-----------------------------------------------------------------------
--- Metalua.
---
--- Summary: parser generator. Collection of higher order functors,
--- which allow to build and combine parsers. Relies on a lexer
--- that supports the same API as the one exposed in mll.lua.
---
-----------------------------------------------------------------------
---
--- Copyright (c) 2006-2008, Fabien Fleutot <metalua@gmail.com>.
---
--- This software is released under the MIT Licence, see licence.txt
--- for details.
---
-----------------------------------------------------------------------
-
---------------------------------------------------------------------------------
---
--- Exported API:
---
--- Parser generators:
--- * [gg.sequence()]
--- * [gg.multisequence()]
--- * [gg.expr()]
--- * [gg.list()]
--- * [gg.onkeyword()]
--- * [gg.optkeyword()]
---
--- Other functions:
--- * [gg.parse_error()]
--- * [gg.make_parser()]
--- * [gg.is_parser()]
---
---------------------------------------------------------------------------------
-
-module("gg", package.seeall)
-
--------------------------------------------------------------------------------
--- parser metatable, which maps __call to method parse, and adds some
--- error tracing boilerplate.
--------------------------------------------------------------------------------
-local parser_metatable = { }
-function parser_metatable.__call (parser, lx, ...)
- --printf ("Call parser %q of type %q", parser.name or "?", parser.kind)
- if mlc.metabugs then
- return parser:parse (lx, ...)
- --local x = parser:parse (lx, ...)
- --printf ("Result of parser %q: %s",
- -- parser.name or "?",
- -- _G.table.tostring(x, "nohash", 80))
- --return x
- else
- local li = lx:lineinfo_right() or { "?", "?", "?", "?" }
- local status, ast = pcall (parser.parse, parser, lx, ...)
- if status then return ast else
- error (string.format ("%s\n - (l.%s, c.%s, k.%s) in parser %s",
- ast:strmatch "gg.lua:%d+: (.*)" or ast,
- li[1], li[2], li[3], parser.name or parser.kind))
- end
- end
-end
-
--------------------------------------------------------------------------------
--- Turn a table into a parser, mainly by setting the metatable.
--------------------------------------------------------------------------------
-function make_parser(kind, p)
- p.kind = kind
- if not p.transformers then p.transformers = { } end
- function p.transformers:add (x)
- table.insert (self, x)
- end
- setmetatable (p, parser_metatable)
- return p
-end
-
--------------------------------------------------------------------------------
--- Return true iff [x] is a parser.
--- If it's a gg-generated parser, reutrn the name of its kind.
--------------------------------------------------------------------------------
-function is_parser (x)
- return type(x)=="function" or getmetatable(x)==parser_metatable and x.kind
-end
-
--------------------------------------------------------------------------------
--- Parse a sequence, without applying builder nor transformers
--------------------------------------------------------------------------------
-local function raw_parse_sequence (lx, p)
- local r = { }
- for i=1, #p do
- e=p[i]
- if type(e) == "string" then
- if not lx:is_keyword (lx:next(), e) then
- parse_error (lx, "Keyword '%s' expected", e) end
- elseif is_parser (e) then
- table.insert (r, e (lx))
- else
- gg.parse_error (lx,"Sequence `%s': element #%i is not a string "..
- "nor a parser: %s",
- p.name, i, table.tostring(e))
- end
- end
- return r
-end
-
--------------------------------------------------------------------------------
--- Parse a multisequence, without applying multisequence transformers.
--- The sequences are completely parsed.
--------------------------------------------------------------------------------
-local function raw_parse_multisequence (lx, sequence_table, default)
- local seq_parser = sequence_table[lx:is_keyword(lx:peek())]
- if seq_parser then return seq_parser (lx)
- elseif default then return default (lx)
- else return false end
-end
-
--------------------------------------------------------------------------------
--- Applies all transformers listed in parser on ast.
--------------------------------------------------------------------------------
-local function transform (ast, parser, fli, lli)
- if parser.transformers then
- for _, t in ipairs (parser.transformers) do ast = t(ast) or ast end
- end
- if type(ast) == 'table'then
- local ali = ast.lineinfo
- if not ali or ali.first~=fli or ali.last~=lli then
- ast.lineinfo = { first = fli, last = lli }
- end
- end
- return ast
-end
-
--------------------------------------------------------------------------------
--- Generate a tracable parsing error (not implemented yet)
--------------------------------------------------------------------------------
-function parse_error(lx, fmt, ...)
- local li = lx:lineinfo_left() or {-1,-1,-1, "<unknown file>"}
- local msg = string.format("line %i, char %i: "..fmt, li[1], li[2], ...)
- local src = lx.src
- if li[3]>0 and src then
- local i, j = li[3], li[3]
- while src:sub(i,i) ~= '\n' and i>=0 do i=i-1 end
- while src:sub(j,j) ~= '\n' and j<=#src do j=j+1 end
- local srcline = src:sub (i+1, j-1)
- local idx = string.rep (" ", li[2]).."^"
- msg = string.format("%s\n>>> %s\n>>> %s", msg, srcline, idx)
- end
- error(msg)
-end
-
--------------------------------------------------------------------------------
---
--- Sequence parser generator
---
--------------------------------------------------------------------------------
--- Input fields:
---
--- * [builder]: how to build an AST out of sequence parts. let [x] be the list
--- of subparser results (keywords are simply omitted). [builder] can be:
--- - [nil], in which case the result of parsing is simply [x]
--- - a string, which is then put as a tag on [x]
--- - a function, which takes [x] as a parameter and returns an AST.
---
--- * [name]: the name of the parser. Used for debug messages
---
--- * [transformers]: a list of AST->AST functions, applied in order on ASTs
--- returned by the parser.
---
--- * Table-part entries corresponds to keywords (strings) and subparsers
--- (function and callable objects).
---
--- After creation, the following fields are added:
--- * [parse] the parsing function lexer->AST
--- * [kind] == "sequence"
--- * [name] is set, if it wasn't in the input.
---
--------------------------------------------------------------------------------
-function sequence (p)
- make_parser ("sequence", p)
-
- -------------------------------------------------------------------
- -- Parsing method
- -------------------------------------------------------------------
- function p:parse (lx)
- -- Raw parsing:
- local fli = lx:lineinfo_right()
- local seq = raw_parse_sequence (lx, self)
- local lli = lx:lineinfo_left()
-
- -- Builder application:
- local builder, tb = self.builder, type (self.builder)
- if tb == "string" then seq.tag = builder
- elseif tb == "function" or builder and builder.__call then seq = builder(seq)
- elseif builder == nil then -- nothing
- else error ("Invalid builder of type "..tb.." in sequence") end
- seq = transform (seq, self, fli, lli)
- assert (not seq or seq.lineinfo)
- return seq
- end
-
- -------------------------------------------------------------------
- -- Construction
- -------------------------------------------------------------------
- -- Try to build a proper name
- if not p.name and type(p[1])=="string" then
- p.name = p[1].." ..."
- if type(p[#p])=="string" then p.name = p.name .. " " .. p[#p] end
- else
- p.name = "<anonymous>"
- end
-
- return p
-end --</sequence>
-
-
--------------------------------------------------------------------------------
---
--- Multiple, keyword-driven, sequence parser generator
---
--------------------------------------------------------------------------------
--- in [p], useful fields are:
---
--- * [transformers]: as usual
---
--- * [name]: as usual
---
--- * Table-part entries must be sequence parsers, or tables which can
--- be turned into a sequence parser by [gg.sequence]. These
--- sequences must start with a keyword, and this initial keyword
--- must be different for each sequence. The table-part entries will
--- be removed after [gg.multisequence] returns.
---
--- * [default]: the parser to run if the next keyword in the lexer is
--- none of the registered initial keywords. If there's no default
--- parser and no suitable initial keyword, the multisequence parser
--- simply returns [false].
---
--- After creation, the following fields are added:
---
--- * [parse] the parsing function lexer->AST
---
--- * [sequences] the table of sequences, indexed by initial keywords.
---
--- * [add] method takes a sequence parser or a config table for
--- [gg.sequence], and adds/replaces the corresponding sequence
--- parser. If the keyword was already used, the former sequence is
--- removed and a warning is issued.
---
--- * [get] method returns a sequence by its initial keyword
---
--- * [kind] == "multisequence"
---
--------------------------------------------------------------------------------
-function multisequence (p)
- make_parser ("multisequence", p)
-
- -------------------------------------------------------------------
- -- Add a sequence (might be just a config table for [gg.sequence])
- -------------------------------------------------------------------
- function p:add (s)
- -- compile if necessary:
- if not is_parser(s) then sequence(s) end
- if type(s[1]) ~= "string" then
- error "Invalid sequence for multiseq"
- elseif self.sequences[s[1]] then
- printf (" *** Warning: keyword %q overloaded in multisequence ***", s[1])
- end
- self.sequences[s[1]] = s
- end -- </multisequence.add>
-
- -------------------------------------------------------------------
- -- Get the sequence starting with this keyword. [kw :: string]
- -------------------------------------------------------------------
- function p:get (kw) return self.sequences [kw] end
-
- -------------------------------------------------------------------
- -- Remove the sequence starting with keyword [kw :: string]
- -------------------------------------------------------------------
- function p:del (kw)
- if not self.sequences[kw] then
- printf("*** Warning: trying to delete sequence starting "..
- "with %q from a multisequence having no such "..
- "entry ***", kw) end
- local removed = self.sequences[kw]
- self.sequences[kw] = nil
- return removed
- end
-
- -------------------------------------------------------------------
- -- Parsing method
- -------------------------------------------------------------------
- function p:parse (lx)
- local fli = lx:lineinfo_right()
- local x = raw_parse_multisequence (lx, self.sequences, self.default)
- local lli = lx:lineinfo_left()
- return transform (x, self, fli, lli)
- end
-
- -------------------------------------------------------------------
- -- Construction
- -------------------------------------------------------------------
- -- Register the sequences passed to the constructor. They're going
- -- from the array part of the parser to the hash part of field
- -- [sequences]
- p.sequences = { }
- for i=1, #p do p:add (p[i]); p[i] = nil end
-
- -- FIXME: why is this commented out?
- --if p.default and not is_parser(p.default) then sequence(p.default) end
- return p
-end --</multisequence>
-
-
--------------------------------------------------------------------------------
---
--- Expression parser generator
---
--------------------------------------------------------------------------------
---
--- Expression configuration relies on three tables: [prefix], [infix]
--- and [suffix]. Moreover, the primary parser can be replaced by a
--- table: in this case the [primary] table will be passed to
--- [gg.multisequence] to create a parser.
---
--- Each of these tables is a modified multisequence parser: the
--- differences with respect to regular multisequence config tables are:
---
--- * the builder takes specific parameters:
--- - for [prefix], it takes the result of the prefix sequence parser,
--- and the prefixed expression
--- - for [infix], it takes the left-hand-side expression, the results
--- of the infix sequence parser, and the right-hand-side expression.
--- - for [suffix], it takes the suffixed expression, and theresult
--- of the suffix sequence parser.
---
--- * the default field is a list, with parameters:
--- - [parser] the raw parsing function
--- - [transformers], as usual
--- - [prec], the operator's precedence
--- - [assoc] for [infix] table, the operator's associativity, which
--- can be "left", "right" or "flat" (default to left)
---
--- In [p], useful fields are:
--- * [transformers]: as usual
--- * [name]: as usual
--- * [primary]: the atomic expression parser, or a multisequence config
--- table (mandatory)
--- * [prefix]: prefix operators config table, see above.
--- * [infix]: infix operators config table, see above.
--- * [suffix]: suffix operators config table, see above.
---
--- After creation, these fields are added:
--- * [kind] == "expr"
--- * [parse] as usual
--- * each table is turned into a multisequence, and therefore has an
--- [add] method
---
--------------------------------------------------------------------------------
-function expr (p)
- make_parser ("expr", p)
-
- -------------------------------------------------------------------
- -- parser method.
- -- In addition to the lexer, it takes an optional precedence:
- -- it won't read expressions whose precedence is lower or equal
- -- to [prec].
- -------------------------------------------------------------------
- function p:parse (lx, prec)
- prec = prec or 0
-
- ------------------------------------------------------
- -- Extract the right parser and the corresponding
- -- options table, for (pre|in|suff)fix operators.
- -- Options include prec, assoc, transformers.
- ------------------------------------------------------
- local function get_parser_info (tab)
- local p2 = tab:get (lx:is_keyword (lx:peek()))
- if p2 then -- keyword-based sequence found
- local function parser(lx) return raw_parse_sequence(lx, p2) end
- return parser, p2
- else -- Got to use the default parser
- local d = tab.default
- if d then return d.parse or d.parser, d
- else return false, false end
- end
- end
-
- ------------------------------------------------------
- -- Look for a prefix sequence. Multiple prefixes are
- -- handled through the recursive [p.parse] call.
- -- Notice the double-transform: one for the primary
- -- expr, and one for the one with the prefix op.
- ------------------------------------------------------
- local function handle_prefix ()
- local fli = lx:lineinfo_right()
- local p2_func, p2 = get_parser_info (self.prefix)
- local op = p2_func and p2_func (lx)
- if op then -- Keyword-based sequence found
- local ili = lx:lineinfo_right() -- Intermediate LineInfo
- local e = p2.builder (op, self:parse (lx, p2.prec))
- local lli = lx:lineinfo_left()
- return transform (transform (e, p2, ili, lli), self, fli, lli)
- else -- No prefix found, get a primary expression
- local e = self.primary(lx)
- local lli = lx:lineinfo_left()
- return transform (e, self, fli, lli)
- end
- end --</expr.parse.handle_prefix>
-
- ------------------------------------------------------
- -- Look for an infix sequence+right-hand-side operand.
- -- Return the whole binary expression result,
- -- or false if no operator was found.
- ------------------------------------------------------
- local function handle_infix (e)
- local p2_func, p2 = get_parser_info (self.infix)
- if not p2 then return false end
-
- -----------------------------------------
- -- Handle flattening operators: gather all operands
- -- of the series in [list]; when a different operator
- -- is found, stop, build from [list], [transform] and
- -- return.
- -----------------------------------------
- if (not p2.prec or p2.prec>prec) and p2.assoc=="flat" then
- local fli = lx:lineinfo_right()
- local pflat, list = p2, { e }
- repeat
- local op = p2_func(lx)
- if not op then break end
- table.insert (list, self:parse (lx, p2.prec))
- local _ -- We only care about checking that p2==pflat
- _, p2 = get_parser_info (self.infix)
- until p2 ~= pflat
- local e2 = pflat.builder (list)
- local lli = lx:lineinfo_left()
- return transform (transform (e2, pflat, fli, lli), self, fli, lli)
-
- -----------------------------------------
- -- Handle regular infix operators: [e] the LHS is known,
- -- just gather the operator and [e2] the RHS.
- -- Result goes in [e3].
- -----------------------------------------
- elseif p2.prec and p2.prec>prec or
- p2.prec==prec and p2.assoc=="right" then
- local fli = e.lineinfo.first -- lx:lineinfo_right()
- local op = p2_func(lx)
- if not op then return false end
- local e2 = self:parse (lx, p2.prec)
- local e3 = p2.builder (e, op, e2)
- local lli = lx:lineinfo_left()
- return transform (transform (e3, p2, fli, lli), self, fli, lli)
-
- -----------------------------------------
- -- Check for non-associative operators, and complain if applicable.
- -----------------------------------------
- elseif p2.assoc=="none" and p2.prec==prec then
- parser_error (lx, "non-associative operator!")
-
- -----------------------------------------
- -- No infix operator suitable at that precedence
- -----------------------------------------
- else return false end
-
- end --</expr.parse.handle_infix>
-
- ------------------------------------------------------
- -- Look for a suffix sequence.
- -- Return the result of suffix operator on [e],
- -- or false if no operator was found.
- ------------------------------------------------------
- local function handle_suffix (e)
- -- FIXME bad fli, must take e.lineinfo.first
- local p2_func, p2 = get_parser_info (self.suffix)
- if not p2 then return false end
- if not p2.prec or p2.prec>=prec then
- --local fli = lx:lineinfo_right()
- local fli = e.lineinfo.first
- local op = p2_func(lx)
- if not op then return false end
- local lli = lx:lineinfo_left()
- e = p2.builder (e, op)
- e = transform (transform (e, p2, fli, lli), self, fli, lli)
- return e
- end
- return false
- end --</expr.parse.handle_suffix>
-
- ------------------------------------------------------
- -- Parser body: read suffix and (infix+operand)
- -- extensions as long as we're able to fetch more at
- -- this precedence level.
- ------------------------------------------------------
- local e = handle_prefix()
- repeat
- local x = handle_suffix (e); e = x or e
- local y = handle_infix (e); e = y or e
- until not (x or y)
-
- -- No transform: it already happened in operators handling
- return e
- end --</expr.parse>
-
- -------------------------------------------------------------------
- -- Construction
- -------------------------------------------------------------------
- if not p.primary then p.primary=p[1]; p[1]=nil end
- for _, t in ipairs{ "primary", "prefix", "infix", "suffix" } do
- if not p[t] then p[t] = { } end
- if not is_parser(p[t]) then multisequence(p[t]) end
- end
- function p:add(...) return self.primary:add(...) end
- return p
-end --</expr>
-
-
--------------------------------------------------------------------------------
---
--- List parser generator
---
--------------------------------------------------------------------------------
--- In [p], the following fields can be provided in input:
---
--- * [builder]: takes list of subparser results, returns AST
--- * [transformers]: as usual
--- * [name]: as usual
---
--- * [terminators]: list of strings representing the keywords which
--- might mark the end of the list. When non-empty, the list is
--- allowed to be empty. A string is treated as a single-element
--- table, whose element is that string, e.g. ["do"] is the same as
--- [{"do"}].
---
--- * [separators]: list of strings representing the keywords which can
--- separate elements of the list. When non-empty, one of these
--- keyword has to be found between each element. Lack of a separator
--- indicates the end of the list. A string is treated as a
--- single-element table, whose element is that string, e.g. ["do"]
--- is the same as [{"do"}]. If [terminators] is empty/nil, then
--- [separators] has to be non-empty.
---
--- After creation, the following fields are added:
--- * [parse] the parsing function lexer->AST
--- * [kind] == "list"
---
--------------------------------------------------------------------------------
-function list (p)
- make_parser ("list", p)
-
- -------------------------------------------------------------------
- -- Parsing method
- -------------------------------------------------------------------
- function p:parse (lx)
-
- ------------------------------------------------------
- -- Used to quickly check whether there's a terminator
- -- or a separator immediately ahead
- ------------------------------------------------------
- local function peek_is_in (keywords)
- return keywords and lx:is_keyword(lx:peek(), unpack(keywords)) end
-
- local x = { }
- local fli = lx:lineinfo_right()
-
- -- if there's a terminator to start with, don't bother trying
- if not peek_is_in (self.terminators) then
- repeat table.insert (x, self.primary (lx)) -- read one element
- until
- -- First reason to stop: There's a separator list specified,
- -- and next token isn't one. Otherwise, consume it with [lx:next()]
- self.separators and not(peek_is_in (self.separators) and lx:next()) or
- -- Other reason to stop: terminator token ahead
- peek_is_in (self.terminators) or
- -- Last reason: end of file reached
- lx:peek().tag=="Eof"
- end
-
- local lli = lx:lineinfo_left()
-
- -- Apply the builder. It can be a string, or a callable value,
- -- or simply nothing.
- local b = self.builder
- if b then
- if type(b)=="string" then x.tag = b -- b is a string, use it as a tag
- elseif type(b)=="function" then x=b(x)
- else
- local bmt = getmetatable(b)
- if bmt and bmt.__call then x=b(x) end
- end
- end
- return transform (x, self, fli, lli)
- end --</list.parse>
-
- -------------------------------------------------------------------
- -- Construction
- -------------------------------------------------------------------
- if not p.primary then p.primary = p[1]; p[1] = nil end
- if type(p.terminators) == "string" then p.terminators = { p.terminators }
- elseif p.terminators and #p.terminators == 0 then p.terminators = nil end
- if type(p.separators) == "string" then p.separators = { p.separators }
- elseif p.separators and #p.separators == 0 then p.separators = nil end
-
- return p
-end --</list>
-
-
--------------------------------------------------------------------------------
---
--- Keyword-conditionned parser generator
---
--------------------------------------------------------------------------------
---
--- Only apply a parser if a given keyword is found. The result of
--- [gg.onkeyword] parser is the result of the subparser (modulo
--- [transformers] applications).
---
--- lineinfo: the keyword is *not* included in the boundaries of the
--- resulting lineinfo. A review of all usages of gg.onkeyword() in the
--- implementation of metalua has shown that it was the appropriate choice
--- in every case.
---
--- Input fields:
---
--- * [name]: as usual
---
--- * [transformers]: as usual
---
--- * [peek]: if non-nil, the conditionning keyword is left in the lexeme
--- stream instead of being consumed.
---
--- * [primary]: the subparser.
---
--- * [keywords]: list of strings representing triggering keywords.
---
--- * Table-part entries can contain strings, and/or exactly one parser.
--- Strings are put in [keywords], and the parser is put in [primary].
---
--- After the call, the following fields will be set:
---
--- * [parse] the parsing method
--- * [kind] == "onkeyword"
--- * [primary]
--- * [keywords]
---
--------------------------------------------------------------------------------
-function onkeyword (p)
- make_parser ("onkeyword", p)
-
- -------------------------------------------------------------------
- -- Parsing method
- -------------------------------------------------------------------
- function p:parse(lx)
- if lx:is_keyword (lx:peek(), unpack(self.keywords)) then
- --local fli = lx:lineinfo_right()
- if not self.peek then lx:next() end
- local content = self.primary (lx)
- --local lli = lx:lineinfo_left()
- local fli, lli = content.lineinfo.first, content.lineinfo.last
- return transform (content, p, fli, lli)
- else return false end
- end
-
- -------------------------------------------------------------------
- -- Construction
- -------------------------------------------------------------------
- if not p.keywords then p.keywords = { } end
- for _, x in ipairs(p) do
- if type(x)=="string" then table.insert (p.keywords, x)
- else assert (not p.primary and is_parser (x)); p.primary = x end
- end
- assert (p.primary, 'no primary parser in gg.onkeyword')
- return p
-end --</onkeyword>
-
-
--------------------------------------------------------------------------------
---
--- Optional keyword consummer pseudo-parser generator
---
--------------------------------------------------------------------------------
---
--- This doesn't return a real parser, just a function. That function parses
--- one of the keywords passed as parameters, and returns it. It returns
--- [false] if no matching keyword is found.
---
--- Notice that tokens returned by lexer already carry lineinfo, therefore
--- there's no need to add them, as done usually through transform() calls.
--------------------------------------------------------------------------------
-function optkeyword (...)
- local args = {...}
- if type (args[1]) == "table" then
- assert (#args == 1)
- args = args[1]
- end
- for _, v in ipairs(args) do assert (type(v)=="string") end
- return function (lx)
- local x = lx:is_keyword (lx:peek(), unpack (args))
- if x then lx:next(); return x
- else return false end
- end
-end
-
-
--------------------------------------------------------------------------------
---
--- Run a parser with a special lexer
---
--------------------------------------------------------------------------------
---
--- This doesn't return a real parser, just a function.
--- First argument is the lexer class to be used with the parser,
--- 2nd is the parser itself.
--- The resulting parser returns whatever the argument parser does.
---
--------------------------------------------------------------------------------
-function with_lexer(new_lexer, parser)
-
- -------------------------------------------------------------------
- -- Most gg functions take their parameters in a table, so it's
- -- better to silently accept when with_lexer{ } is called with
- -- its arguments in a list:
- -------------------------------------------------------------------
- if not parser and #new_lexer==2 and type(new_lexer[1])=='table' then
- return with_lexer(unpack(new_lexer))
- end
-
- -------------------------------------------------------------------
- -- Save the current lexer, switch it for the new one, run the parser,
- -- restore the previous lexer, even if the parser caused an error.
- -------------------------------------------------------------------
- return function (lx)
- local old_lexer = getmetatable(lx)
- lx:sync()
- setmetatable(lx, new_lexer)
- local status, result = pcall(parser, lx)
- lx:sync()
- setmetatable(lx, old_lexer)
- if status then return result else error(result) end
- end
-end
+----------------------------------------------------------------------\r
+-- Metalua.\r
+--\r
+-- Summary: parser generator. Collection of higher order functors,\r
+-- which allow to build and combine parsers. Relies on a lexer\r
+-- that supports the same API as the one exposed in mll.lua.\r
+--\r
+----------------------------------------------------------------------\r
+--\r
+-- Copyright (c) 2006-2008, Fabien Fleutot <metalua@gmail.com>.\r
+--\r
+-- This software is released under the MIT Licence, see licence.txt\r
+-- for details.\r
+--\r
+----------------------------------------------------------------------\r
+\r
+--------------------------------------------------------------------------------\r
+--\r
+-- Exported API:\r
+--\r
+-- Parser generators:\r
+-- * [gg.sequence()]\r
+-- * [gg.multisequence()]\r
+-- * [gg.expr()]\r
+-- * [gg.list()]\r
+-- * [gg.onkeyword()]\r
+-- * [gg.optkeyword()]\r
+--\r
+-- Other functions: \r
+-- * [gg.parse_error()]\r
+-- * [gg.make_parser()]\r
+-- * [gg.is_parser()]\r
+--\r
+--------------------------------------------------------------------------------\r
+\r
+module("gg", package.seeall)\r
+\r
+-------------------------------------------------------------------------------\r
+-- parser metatable, which maps __call to method parse, and adds some\r
+-- error tracing boilerplate.\r
+-------------------------------------------------------------------------------\r
+local parser_metatable = { }\r
+function parser_metatable.__call (parser, lx, ...)\r
+ --printf ("Call parser %q of type %q", parser.name or "?", parser.kind)\r
+ if mlc.metabugs then \r
+ return parser:parse (lx, ...) \r
+ --local x = parser:parse (lx, ...) \r
+ --printf ("Result of parser %q: %s", \r
+ -- parser.name or "?",\r
+ -- _G.table.tostring(x, "nohash", 80))\r
+ --return x\r
+ else\r
+ local li = lx:lineinfo_right() or { "?", "?", "?", "?" }\r
+ local status, ast = pcall (parser.parse, parser, lx, ...) \r
+ if status then return ast else\r
+ error (string.format ("%s\n - (l.%s, c.%s, k.%s) in parser %s", \r
+ ast:strmatch "gg.lua:%d+: (.*)" or ast,\r
+ li[1], li[2], li[3], parser.name or parser.kind))\r
+ end\r
+ end\r
+end\r
+\r
+-------------------------------------------------------------------------------\r
+-- Turn a table into a parser, mainly by setting the metatable.\r
+-------------------------------------------------------------------------------\r
+function make_parser(kind, p)\r
+ p.kind = kind\r
+ if not p.transformers then p.transformers = { } end\r
+ function p.transformers:add (x)\r
+ table.insert (self, x)\r
+ end\r
+ setmetatable (p, parser_metatable)\r
+ return p\r
+end\r
+\r
+-------------------------------------------------------------------------------\r
+-- Return true iff [x] is a parser.\r
+-- If it's a gg-generated parser, reutrn the name of its kind.\r
+-------------------------------------------------------------------------------\r
+function is_parser (x)\r
+ return type(x)=="function" or getmetatable(x)==parser_metatable and x.kind\r
+end\r
+\r
+-------------------------------------------------------------------------------\r
+-- Parse a sequence, without applying builder nor transformers\r
+-------------------------------------------------------------------------------\r
+local function raw_parse_sequence (lx, p)\r
+ local r = { }\r
+ for i=1, #p do\r
+ e=p[i]\r
+ if type(e) == "string" then \r
+ if not lx:is_keyword (lx:next(), e) then\r
+ parse_error (lx, "Keyword '%s' expected", e) end\r
+ elseif is_parser (e) then\r
+ table.insert (r, e (lx)) \r
+ else \r
+ gg.parse_error (lx,"Sequence `%s': element #%i is not a string "..\r
+ "nor a parser: %s", \r
+ p.name, i, table.tostring(e))\r
+ end\r
+ end\r
+ return r\r
+end\r
+\r
+-------------------------------------------------------------------------------\r
+-- Parse a multisequence, without applying multisequence transformers.\r
+-- The sequences are completely parsed.\r
+-------------------------------------------------------------------------------\r
+local function raw_parse_multisequence (lx, sequence_table, default)\r
+ local seq_parser = sequence_table[lx:is_keyword(lx:peek())]\r
+ if seq_parser then return seq_parser (lx)\r
+ elseif default then return default (lx)\r
+ else return false end\r
+end\r
+\r
+-------------------------------------------------------------------------------\r
+-- Applies all transformers listed in parser on ast.\r
+-------------------------------------------------------------------------------\r
+local function transform (ast, parser, fli, lli)\r
+ if parser.transformers then\r
+ for _, t in ipairs (parser.transformers) do ast = t(ast) or ast end\r
+ end\r
+ if type(ast) == 'table'then\r
+ local ali = ast.lineinfo\r
+ if not ali or ali.first~=fli or ali.last~=lli then\r
+ ast.lineinfo = { first = fli, last = lli }\r
+ end\r
+ end\r
+ return ast\r
+end\r
+\r
+-------------------------------------------------------------------------------\r
+-- Generate a tracable parsing error (not implemented yet)\r
+-------------------------------------------------------------------------------\r
+function parse_error(lx, fmt, ...)\r
+ local li = lx:lineinfo_left() or {-1,-1,-1, "<unknown file>"}\r
+ local msg = string.format("line %i, char %i: "..fmt, li[1], li[2], ...) \r
+ local src = lx.src\r
+ if li[3]>0 and src then\r
+ local i, j = li[3], li[3]\r
+ while src:sub(i,i) ~= '\n' and i>=0 do i=i-1 end\r
+ while src:sub(j,j) ~= '\n' and j<=#src do j=j+1 end \r
+ local srcline = src:sub (i+1, j-1)\r
+ local idx = string.rep (" ", li[2]).."^"\r
+ msg = string.format("%s\n>>> %s\n>>> %s", msg, srcline, idx)\r
+ end\r
+ error(msg)\r
+end\r
+ \r
+-------------------------------------------------------------------------------\r
+--\r
+-- Sequence parser generator\r
+--\r
+-------------------------------------------------------------------------------\r
+-- Input fields:\r
+--\r
+-- * [builder]: how to build an AST out of sequence parts. let [x] be the list\r
+-- of subparser results (keywords are simply omitted). [builder] can be:\r
+-- - [nil], in which case the result of parsing is simply [x]\r
+-- - a string, which is then put as a tag on [x]\r
+-- - a function, which takes [x] as a parameter and returns an AST.\r
+--\r
+-- * [name]: the name of the parser. Used for debug messages\r
+--\r
+-- * [transformers]: a list of AST->AST functions, applied in order on ASTs\r
+-- returned by the parser.\r
+--\r
+-- * Table-part entries corresponds to keywords (strings) and subparsers \r
+-- (function and callable objects).\r
+--\r
+-- After creation, the following fields are added:\r
+-- * [parse] the parsing function lexer->AST\r
+-- * [kind] == "sequence"\r
+-- * [name] is set, if it wasn't in the input.\r
+--\r
+-------------------------------------------------------------------------------\r
+function sequence (p)\r
+ make_parser ("sequence", p)\r
+\r
+ -------------------------------------------------------------------\r
+ -- Parsing method\r
+ -------------------------------------------------------------------\r
+ function p:parse (lx)\r
+ -- Raw parsing:\r
+ local fli = lx:lineinfo_right()\r
+ local seq = raw_parse_sequence (lx, self)\r
+ local lli = lx:lineinfo_left()\r
+\r
+ -- Builder application:\r
+ local builder, tb = self.builder, type (self.builder)\r
+ if tb == "string" then seq.tag = builder\r
+ elseif tb == "function" or builder and builder.__call then seq = builder(seq)\r
+ elseif builder == nil then -- nothing\r
+ else error ("Invalid builder of type "..tb.." in sequence") end\r
+ seq = transform (seq, self, fli, lli)\r
+ assert (not seq or seq.lineinfo)\r
+ return seq\r
+ end\r
+\r
+ -------------------------------------------------------------------\r
+ -- Construction\r
+ -------------------------------------------------------------------\r
+ -- Try to build a proper name\r
+ if not p.name and type(p[1])=="string" then \r
+ p.name = p[1].." ..." \r
+ if type(p[#p])=="string" then p.name = p.name .. " " .. p[#p] end\r
+ else\r
+ p.name = "<anonymous>"\r
+ end\r
+\r
+ return p\r
+end --</sequence>\r
+\r
+\r
+-------------------------------------------------------------------------------\r
+--\r
+-- Multiple, keyword-driven, sequence parser generator\r
+--\r
+-------------------------------------------------------------------------------\r
+-- in [p], useful fields are:\r
+--\r
+-- * [transformers]: as usual\r
+--\r
+-- * [name]: as usual\r
+--\r
+-- * Table-part entries must be sequence parsers, or tables which can\r
+-- be turned into a sequence parser by [gg.sequence]. These\r
+-- sequences must start with a keyword, and this initial keyword\r
+-- must be different for each sequence. The table-part entries will\r
+-- be removed after [gg.multisequence] returns.\r
+--\r
+-- * [default]: the parser to run if the next keyword in the lexer is\r
+-- none of the registered initial keywords. If there's no default\r
+-- parser and no suitable initial keyword, the multisequence parser\r
+-- simply returns [false].\r
+--\r
+-- After creation, the following fields are added:\r
+--\r
+-- * [parse] the parsing function lexer->AST\r
+--\r
+-- * [sequences] the table of sequences, indexed by initial keywords.\r
+--\r
+-- * [add] method takes a sequence parser or a config table for\r
+-- [gg.sequence], and adds/replaces the corresponding sequence\r
+-- parser. If the keyword was already used, the former sequence is\r
+-- removed and a warning is issued.\r
+--\r
+-- * [get] method returns a sequence by its initial keyword\r
+--\r
+-- * [kind] == "multisequence"\r
+--\r
+-------------------------------------------------------------------------------\r
+function multisequence (p) \r
+ make_parser ("multisequence", p)\r
+\r
+ -------------------------------------------------------------------\r
+ -- Add a sequence (might be just a config table for [gg.sequence])\r
+ -------------------------------------------------------------------\r
+ function p:add (s)\r
+ -- compile if necessary:\r
+ if not is_parser(s) then sequence(s) end\r
+ if type(s[1]) ~= "string" then \r
+ error "Invalid sequence for multiseq"\r
+ elseif self.sequences[s[1]] then \r
+ eprintf (" *** Warning: keyword %q overloaded in multisequence ***", s[1])\r
+ end\r
+ self.sequences[s[1]] = s\r
+ end -- </multisequence.add>\r
+\r
+ -------------------------------------------------------------------\r
+ -- Get the sequence starting with this keyword. [kw :: string]\r
+ -------------------------------------------------------------------\r
+ function p:get (kw) return self.sequences [kw] end\r
+\r
+ -------------------------------------------------------------------\r
+ -- Remove the sequence starting with keyword [kw :: string]\r
+ -------------------------------------------------------------------\r
+ function p:del (kw) \r
+ if not self.sequences[kw] then \r
+ eprintf("*** Warning: trying to delete sequence starting "..\r
+ "with %q from a multisequence having no such "..\r
+ "entry ***", kw) end\r
+ local removed = self.sequences[kw]\r
+ self.sequences[kw] = nil \r
+ return removed\r
+ end\r
+\r
+ -------------------------------------------------------------------\r
+ -- Parsing method\r
+ -------------------------------------------------------------------\r
+ function p:parse (lx)\r
+ local fli = lx:lineinfo_right()\r
+ local x = raw_parse_multisequence (lx, self.sequences, self.default)\r
+ local lli = lx:lineinfo_left()\r
+ return transform (x, self, fli, lli)\r
+ end\r
+\r
+ -------------------------------------------------------------------\r
+ -- Construction\r
+ -------------------------------------------------------------------\r
+ -- Register the sequences passed to the constructor. They're going\r
+ -- from the array part of the parser to the hash part of field\r
+ -- [sequences]\r
+ p.sequences = { }\r
+ for i=1, #p do p:add (p[i]); p[i] = nil end\r
+\r
+ -- FIXME: why is this commented out?\r
+ --if p.default and not is_parser(p.default) then sequence(p.default) end\r
+ return p\r
+end --</multisequence>\r
+\r
+\r
+-------------------------------------------------------------------------------\r
+--\r
+-- Expression parser generator\r
+--\r
+-------------------------------------------------------------------------------\r
+--\r
+-- Expression configuration relies on three tables: [prefix], [infix]\r
+-- and [suffix]. Moreover, the primary parser can be replaced by a\r
+-- table: in this case the [primary] table will be passed to\r
+-- [gg.multisequence] to create a parser.\r
+--\r
+-- Each of these tables is a modified multisequence parser: the\r
+-- differences with respect to regular multisequence config tables are:\r
+--\r
+-- * the builder takes specific parameters:\r
+-- - for [prefix], it takes the result of the prefix sequence parser,\r
+-- and the prefixed expression\r
+-- - for [infix], it takes the left-hand-side expression, the results \r
+-- of the infix sequence parser, and the right-hand-side expression.\r
+-- - for [suffix], it takes the suffixed expression, and theresult \r
+-- of the suffix sequence parser.\r
+--\r
+-- * the default field is a list, with parameters:\r
+-- - [parser] the raw parsing function\r
+-- - [transformers], as usual\r
+-- - [prec], the operator's precedence\r
+-- - [assoc] for [infix] table, the operator's associativity, which\r
+-- can be "left", "right" or "flat" (default to left)\r
+--\r
+-- In [p], useful fields are:\r
+-- * [transformers]: as usual\r
+-- * [name]: as usual\r
+-- * [primary]: the atomic expression parser, or a multisequence config \r
+-- table (mandatory)\r
+-- * [prefix]: prefix operators config table, see above.\r
+-- * [infix]: infix operators config table, see above.\r
+-- * [suffix]: suffix operators config table, see above.\r
+--\r
+-- After creation, these fields are added:\r
+-- * [kind] == "expr"\r
+-- * [parse] as usual\r
+-- * each table is turned into a multisequence, and therefore has an \r
+-- [add] method\r
+--\r
+-------------------------------------------------------------------------------\r
+function expr (p)\r
+ make_parser ("expr", p)\r
+\r
+ -------------------------------------------------------------------\r
+ -- parser method.\r
+ -- In addition to the lexer, it takes an optional precedence:\r
+ -- it won't read expressions whose precedence is lower or equal\r
+ -- to [prec].\r
+ -------------------------------------------------------------------\r
+ function p:parse (lx, prec)\r
+ prec = prec or 0\r
+\r
+ ------------------------------------------------------\r
+ -- Extract the right parser and the corresponding\r
+ -- options table, for (pre|in|suff)fix operators.\r
+ -- Options include prec, assoc, transformers.\r
+ ------------------------------------------------------\r
+ local function get_parser_info (tab)\r
+ local p2 = tab:get (lx:is_keyword (lx:peek()))\r
+ if p2 then -- keyword-based sequence found\r
+ local function parser(lx) return raw_parse_sequence(lx, p2) end\r
+ return parser, p2\r
+ else -- Got to use the default parser\r
+ local d = tab.default\r
+ if d then return d.parse or d.parser, d\r
+ else return false, false end\r
+ end\r
+ end\r
+\r
+ ------------------------------------------------------\r
+ -- Look for a prefix sequence. Multiple prefixes are\r
+ -- handled through the recursive [p.parse] call.\r
+ -- Notice the double-transform: one for the primary\r
+ -- expr, and one for the one with the prefix op.\r
+ ------------------------------------------------------\r
+ local function handle_prefix ()\r
+ local fli = lx:lineinfo_right()\r
+ local p2_func, p2 = get_parser_info (self.prefix)\r
+ local op = p2_func and p2_func (lx)\r
+ if op then -- Keyword-based sequence found\r
+ local ili = lx:lineinfo_right() -- Intermediate LineInfo\r
+ local e = p2.builder (op, self:parse (lx, p2.prec))\r
+ local lli = lx:lineinfo_left()\r
+ return transform (transform (e, p2, ili, lli), self, fli, lli)\r
+ else -- No prefix found, get a primary expression \r
+ local e = self.primary(lx)\r
+ local lli = lx:lineinfo_left()\r
+ return transform (e, self, fli, lli)\r
+ end\r
+ end --</expr.parse.handle_prefix>\r
+\r
+ ------------------------------------------------------\r
+ -- Look for an infix sequence+right-hand-side operand.\r
+ -- Return the whole binary expression result,\r
+ -- or false if no operator was found.\r
+ ------------------------------------------------------\r
+ local function handle_infix (e)\r
+ local p2_func, p2 = get_parser_info (self.infix)\r
+ if not p2 then return false end\r
+\r
+ -----------------------------------------\r
+ -- Handle flattening operators: gather all operands\r
+ -- of the series in [list]; when a different operator \r
+ -- is found, stop, build from [list], [transform] and\r
+ -- return.\r
+ -----------------------------------------\r
+ if (not p2.prec or p2.prec>prec) and p2.assoc=="flat" then\r
+ local fli = lx:lineinfo_right()\r
+ local pflat, list = p2, { e }\r
+ repeat\r
+ local op = p2_func(lx)\r
+ if not op then break end\r
+ table.insert (list, self:parse (lx, p2.prec))\r
+ local _ -- We only care about checking that p2==pflat\r
+ _, p2 = get_parser_info (self.infix)\r
+ until p2 ~= pflat\r
+ local e2 = pflat.builder (list)\r
+ local lli = lx:lineinfo_left()\r
+ return transform (transform (e2, pflat, fli, lli), self, fli, lli)\r
+ \r
+ -----------------------------------------\r
+ -- Handle regular infix operators: [e] the LHS is known,\r
+ -- just gather the operator and [e2] the RHS.\r
+ -- Result goes in [e3].\r
+ -----------------------------------------\r
+ elseif p2.prec and p2.prec>prec or \r
+ p2.prec==prec and p2.assoc=="right" then\r
+ local fli = e.lineinfo.first -- lx:lineinfo_right()\r
+ local op = p2_func(lx)\r
+ if not op then return false end\r
+ local e2 = self:parse (lx, p2.prec)\r
+ local e3 = p2.builder (e, op, e2)\r
+ local lli = lx:lineinfo_left()\r
+ return transform (transform (e3, p2, fli, lli), self, fli, lli)\r
+\r
+ -----------------------------------------\r
+ -- Check for non-associative operators, and complain if applicable. \r
+ -----------------------------------------\r
+ elseif p2.assoc=="none" and p2.prec==prec then\r
+ parser_error (lx, "non-associative operator!")\r
+\r
+ -----------------------------------------\r
+ -- No infix operator suitable at that precedence\r
+ -----------------------------------------\r
+ else return false end\r
+\r
+ end --</expr.parse.handle_infix>\r
+\r
+ ------------------------------------------------------\r
+ -- Look for a suffix sequence.\r
+ -- Return the result of suffix operator on [e],\r
+ -- or false if no operator was found.\r
+ ------------------------------------------------------\r
+ local function handle_suffix (e)\r
+ -- FIXME bad fli, must take e.lineinfo.first\r
+ local p2_func, p2 = get_parser_info (self.suffix)\r
+ if not p2 then return false end\r
+ if not p2.prec or p2.prec>=prec then\r
+ --local fli = lx:lineinfo_right()\r
+ local fli = e.lineinfo.first\r
+ local op = p2_func(lx)\r
+ if not op then return false end\r
+ local lli = lx:lineinfo_left()\r
+ e = p2.builder (e, op)\r
+ e = transform (transform (e, p2, fli, lli), self, fli, lli)\r
+ return e\r
+ end\r
+ return false\r
+ end --</expr.parse.handle_suffix>\r
+\r
+ ------------------------------------------------------\r
+ -- Parser body: read suffix and (infix+operand) \r
+ -- extensions as long as we're able to fetch more at\r
+ -- this precedence level.\r
+ ------------------------------------------------------\r
+ local e = handle_prefix()\r
+ repeat\r
+ local x = handle_suffix (e); e = x or e\r
+ local y = handle_infix (e); e = y or e\r
+ until not (x or y)\r
+\r
+ -- No transform: it already happened in operators handling\r
+ return e\r
+ end --</expr.parse>\r
+\r
+ -------------------------------------------------------------------\r
+ -- Construction\r
+ -------------------------------------------------------------------\r
+ if not p.primary then p.primary=p[1]; p[1]=nil end\r
+ for _, t in ipairs{ "primary", "prefix", "infix", "suffix" } do\r
+ if not p[t] then p[t] = { } end\r
+ if not is_parser(p[t]) then multisequence(p[t]) end\r
+ end\r
+ function p:add(...) return self.primary:add(...) end\r
+ return p\r
+end --</expr>\r
+\r
+\r
+-------------------------------------------------------------------------------\r
+--\r
+-- List parser generator\r
+--\r
+-------------------------------------------------------------------------------\r
+-- In [p], the following fields can be provided in input:\r
+--\r
+-- * [builder]: takes list of subparser results, returns AST\r
+-- * [transformers]: as usual\r
+-- * [name]: as usual\r
+--\r
+-- * [terminators]: list of strings representing the keywords which\r
+-- might mark the end of the list. When non-empty, the list is\r
+-- allowed to be empty. A string is treated as a single-element\r
+-- table, whose element is that string, e.g. ["do"] is the same as\r
+-- [{"do"}].\r
+--\r
+-- * [separators]: list of strings representing the keywords which can\r
+-- separate elements of the list. When non-empty, one of these\r
+-- keyword has to be found between each element. Lack of a separator\r
+-- indicates the end of the list. A string is treated as a\r
+-- single-element table, whose element is that string, e.g. ["do"]\r
+-- is the same as [{"do"}]. If [terminators] is empty/nil, then\r
+-- [separators] has to be non-empty.\r
+--\r
+-- After creation, the following fields are added:\r
+-- * [parse] the parsing function lexer->AST\r
+-- * [kind] == "list"\r
+--\r
+-------------------------------------------------------------------------------\r
+function list (p)\r
+ make_parser ("list", p)\r
+\r
+ -------------------------------------------------------------------\r
+ -- Parsing method\r
+ -------------------------------------------------------------------\r
+ function p:parse (lx)\r
+\r
+ ------------------------------------------------------\r
+ -- Used to quickly check whether there's a terminator \r
+ -- or a separator immediately ahead\r
+ ------------------------------------------------------\r
+ local function peek_is_in (keywords) \r
+ return keywords and lx:is_keyword(lx:peek(), unpack(keywords)) end\r
+\r
+ local x = { }\r
+ local fli = lx:lineinfo_right()\r
+\r
+ -- if there's a terminator to start with, don't bother trying\r
+ if not peek_is_in (self.terminators) then \r
+ repeat table.insert (x, self.primary (lx)) -- read one element\r
+ until\r
+ -- First reason to stop: There's a separator list specified,\r
+ -- and next token isn't one. Otherwise, consume it with [lx:next()]\r
+ self.separators and not(peek_is_in (self.separators) and lx:next()) or\r
+ -- Other reason to stop: terminator token ahead\r
+ peek_is_in (self.terminators) or\r
+ -- Last reason: end of file reached\r
+ lx:peek().tag=="Eof"\r
+ end\r
+\r
+ local lli = lx:lineinfo_left()\r
+ \r
+ -- Apply the builder. It can be a string, or a callable value, \r
+ -- or simply nothing.\r
+ local b = self.builder\r
+ if b then\r
+ if type(b)=="string" then x.tag = b -- b is a string, use it as a tag\r
+ elseif type(b)=="function" then x=b(x)\r
+ else\r
+ local bmt = getmetatable(b)\r
+ if bmt and bmt.__call then x=b(x) end\r
+ end\r
+ end\r
+ return transform (x, self, fli, lli)\r
+ end --</list.parse>\r
+\r
+ -------------------------------------------------------------------\r
+ -- Construction\r
+ -------------------------------------------------------------------\r
+ if not p.primary then p.primary = p[1]; p[1] = nil end\r
+ if type(p.terminators) == "string" then p.terminators = { p.terminators }\r
+ elseif p.terminators and #p.terminators == 0 then p.terminators = nil end\r
+ if type(p.separators) == "string" then p.separators = { p.separators }\r
+ elseif p.separators and #p.separators == 0 then p.separators = nil end\r
+\r
+ return p\r
+end --</list>\r
+\r
+\r
+-------------------------------------------------------------------------------\r
+--\r
+-- Keyword-conditionned parser generator\r
+--\r
+-------------------------------------------------------------------------------\r
+-- \r
+-- Only apply a parser if a given keyword is found. The result of\r
+-- [gg.onkeyword] parser is the result of the subparser (modulo\r
+-- [transformers] applications).\r
+--\r
+-- lineinfo: the keyword is *not* included in the boundaries of the\r
+-- resulting lineinfo. A review of all usages of gg.onkeyword() in the\r
+-- implementation of metalua has shown that it was the appropriate choice\r
+-- in every case.\r
+--\r
+-- Input fields:\r
+--\r
+-- * [name]: as usual\r
+--\r
+-- * [transformers]: as usual\r
+--\r
+-- * [peek]: if non-nil, the conditionning keyword is left in the lexeme\r
+-- stream instead of being consumed.\r
+--\r
+-- * [primary]: the subparser. \r
+--\r
+-- * [keywords]: list of strings representing triggering keywords.\r
+--\r
+-- * Table-part entries can contain strings, and/or exactly one parser.\r
+-- Strings are put in [keywords], and the parser is put in [primary].\r
+--\r
+-- After the call, the following fields will be set:\r
+-- \r
+-- * [parse] the parsing method\r
+-- * [kind] == "onkeyword"\r
+-- * [primary]\r
+-- * [keywords]\r
+--\r
+-------------------------------------------------------------------------------\r
+function onkeyword (p)\r
+ make_parser ("onkeyword", p)\r
+\r
+ -------------------------------------------------------------------\r
+ -- Parsing method\r
+ -------------------------------------------------------------------\r
+ function p:parse(lx)\r
+ if lx:is_keyword (lx:peek(), unpack(self.keywords)) then\r
+ --local fli = lx:lineinfo_right()\r
+ if not self.peek then lx:next() end\r
+ local content = self.primary (lx)\r
+ --local lli = lx:lineinfo_left()\r
+ local fli, lli = content.lineinfo.first, content.lineinfo.last\r
+ return transform (content, p, fli, lli)\r
+ else return false end\r
+ end\r
+\r
+ -------------------------------------------------------------------\r
+ -- Construction\r
+ -------------------------------------------------------------------\r
+ if not p.keywords then p.keywords = { } end\r
+ for _, x in ipairs(p) do\r
+ if type(x)=="string" then table.insert (p.keywords, x)\r
+ else assert (not p.primary and is_parser (x)); p.primary = x end\r
+ end\r
+ assert (p.primary, 'no primary parser in gg.onkeyword')\r
+ return p\r
+end --</onkeyword>\r
+\r
+\r
+-------------------------------------------------------------------------------\r
+--\r
+-- Optional keyword consummer pseudo-parser generator\r
+--\r
+-------------------------------------------------------------------------------\r
+--\r
+-- This doesn't return a real parser, just a function. That function parses\r
+-- one of the keywords passed as parameters, and returns it. It returns \r
+-- [false] if no matching keyword is found.\r
+--\r
+-- Notice that tokens returned by lexer already carry lineinfo, therefore\r
+-- there's no need to add them, as done usually through transform() calls.\r
+-------------------------------------------------------------------------------\r
+function optkeyword (...)\r
+ local args = {...}\r
+ if type (args[1]) == "table" then \r
+ assert (#args == 1)\r
+ args = args[1]\r
+ end\r
+ for _, v in ipairs(args) do assert (type(v)=="string") end\r
+ return function (lx)\r
+ local x = lx:is_keyword (lx:peek(), unpack (args))\r
+ if x then lx:next(); return x\r
+ else return false end\r
+ end\r
+end\r
+\r
+\r
+-------------------------------------------------------------------------------\r
+--\r
+-- Run a parser with a special lexer\r
+--\r
+-------------------------------------------------------------------------------\r
+--\r
+-- This doesn't return a real parser, just a function.\r
+-- First argument is the lexer class to be used with the parser,\r
+-- 2nd is the parser itself.\r
+-- The resulting parser returns whatever the argument parser does.\r
+--\r
+-------------------------------------------------------------------------------\r
+function with_lexer(new_lexer, parser)\r
+\r
+ -------------------------------------------------------------------\r
+ -- Most gg functions take their parameters in a table, so it's \r
+ -- better to silently accept when with_lexer{ } is called with\r
+ -- its arguments in a list:\r
+ -------------------------------------------------------------------\r
+ if not parser and #new_lexer==2 and type(new_lexer[1])=='table' then\r
+ return with_lexer(unpack(new_lexer))\r
+ end\r
+\r
+ -------------------------------------------------------------------\r
+ -- Save the current lexer, switch it for the new one, run the parser,\r
+ -- restore the previous lexer, even if the parser caused an error.\r
+ -------------------------------------------------------------------\r
+ return function (lx)\r
+ local old_lexer = getmetatable(lx)\r
+ lx:sync()\r
+ setmetatable(lx, new_lexer)\r
+ local status, result = pcall(parser, lx)\r
+ lx:sync()\r
+ setmetatable(lx, old_lexer)\r
+ if status then return result else error(result) end\r
+ end\r
+end\r
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