--- /dev/null
+--------------------------------------------------------------------------------
+-- Copyright (c) 2006-2013 Fabien Fleutot and others.
+--
+-- All rights reserved.
+--
+-- This program and the accompanying materials are made available
+-- under the terms of the Eclipse Public License v1.0 which
+-- accompanies this distribution, and is available at
+-- http://www.eclipse.org/legal/epl-v10.html
+--
+-- This program and the accompanying materials are also made available
+-- under the terms of the MIT public license which accompanies this
+-- distribution, and is available at http://www.lua.org/license.html
+--
+-- Contributors:
+-- Fabien Fleutot - API and implementation
+--
+--------------------------------------------------------------------------------
+
+--------------------------------------------------------------------------------
+--
+-- 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.
+--
+--------------------------------------------------------------------------------
+
+--------------------------------------------------------------------------------
+--
+-- 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()]
+--
+--------------------------------------------------------------------------------
+
+local M = { }
+
+local lexer = require 'metalua.grammar.lexer'
+
+--------------------------------------------------------------------------------
+-- Symbol generator: [gensym()] returns a guaranteed-to-be-unique identifier.
+-- The main purpose is to avoid variable capture in macros.
+--
+-- If a string is passed as an argument, theis string will be part of the
+-- id name (helpful for macro debugging)
+--------------------------------------------------------------------------------
+local gensymidx = 0
+
+function M.gensym (arg)
+ gensymidx = gensymidx + 1
+ return { tag="Id", string.format(".%i.%s", gensymidx, arg or "")}
+end
+
+
+-------------------------------------------------------------------------------
+-- parser metatable, which maps __call to method parse, and adds some
+-- error tracing boilerplate.
+-------------------------------------------------------------------------------
+local parser_metatable = { }
+
+function parser_metatable :__call (lx, ...)
+ return self :parse (lx, ...)
+end
+
+-------------------------------------------------------------------------------
+-- Turn a table into a parser, mainly by setting the metatable.
+-------------------------------------------------------------------------------
+function M.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, return the name of its kind.
+-------------------------------------------------------------------------------
+function M.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
+ local e=p[i]
+ if type(e) == "string" then
+ local kw = lx :next()
+ if not lx :is_keyword (kw, e) then
+ M.parse_error(
+ lx, "A keyword was expected, probably `%s'.", e)
+ end
+ elseif M.is_parser (e) then
+ table.insert (r, e(lx))
+ else -- Invalid parser definition, this is *not* a parsing error
+ error(string.format(
+ "Sequence `%s': element #%i is neither 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 = lexer.new_lineinfo(fli, lli)
+ end
+ end
+ return ast
+end
+
+-------------------------------------------------------------------------------
+-- Generate a tracable parsing error (not implemented yet)
+-------------------------------------------------------------------------------
+function M.parse_error(lx, fmt, ...)
+ local li = lx:lineinfo_left()
+ local file, line, column, offset, positions
+ if li then
+ file, line, column, offset = li.source, li.line, li.column, li.offset
+ positions = { first = li, last = li }
+ else
+ line, column, offset = -1, -1, -1
+ end
+
+ local msg = string.format("line %i, char %i: "..fmt, line, column, ...)
+ if file and file~='?' then msg = "file "..file..", "..msg end
+
+ local src = lx.src
+ if offset>0 and src then
+ local i, j = offset, offset
+ 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 (" ", column).."^"
+ msg = string.format("%s\n>>> %s\n>>> %s", msg, srcline, idx)
+ end
+ --lx :kill()
+ 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 M.sequence (p)
+ M.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 p.name then
+ -- don't touch existing name
+ elseif type(p[1])=="string" then -- find name based on 1st keyword
+ if #p==1 then p.name=p[1]
+ elseif type(p[#p])=="string" then
+ p.name = p[1] .. " ... " .. p[#p]
+ else p.name = p[1] .. " ..." end
+ else -- can't find a decent name
+ p.name = "unnamed_sequence"
+ 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 M.multisequence (p)
+ M.make_parser ("multisequence", p)
+
+ -------------------------------------------------------------------
+ -- Add a sequence (might be just a config table for [gg.sequence])
+ -------------------------------------------------------------------
+ function p :add (s)
+ -- compile if necessary:
+ local keyword = type(s)=='table' and s[1]
+ if type(s)=='table' and not M.is_parser(s) then M.sequence(s) end
+ if M.is_parser(s)~='sequence' or type(keyword)~='string' then
+ if self.default then -- two defaults
+ error ("In a multisequence parser, all but one sequences "..
+ "must start with a keyword")
+ else self.default = s end -- first default
+ else
+ if self.sequences[keyword] then -- duplicate keyword
+ -- TODO: warn that initial keyword `keyword` is overloaded in multiseq
+ end
+ self.sequences[keyword] = s
+ end
+ 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
+ -- TODO: warn that we try to delete a non-existent entry
+ 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 the result
+-- 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 M.expr (p)
+ M.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
+ M.parse_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 M.is_parser(p[t]) then M.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 M.list (p)
+ M.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
+ local is_empty_list = self.terminators and (peek_is_in (self.terminators) or lx:peek().tag=="Eof")
+ if not is_empty_list then
+ repeat
+ local item = self.primary(lx)
+ table.insert (x, item) -- read one element
+ until
+ -- There's a separator list specified, and next token isn't in it.
+ -- Otherwise, consume it with [lx:next()]
+ self.separators and not(peek_is_in (self.separators) and lx:next()) or
+ -- 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-conditioned 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 conditioning 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 M.onkeyword (p)
+ M.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 li = content.lineinfo or { }
+ fli, lli = li.first or fli, li.last or lli
+ 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 M.is_parser (x)); p.primary = x end
+ end
+ assert (next (p.keywords), "Missing trigger keyword in gg.onkeyword")
+ 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 M.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 M.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 M.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
+
+--------------------------------------------------------------------------------
+--
+-- Make sure a parser is used and returns successfully.
+--
+--------------------------------------------------------------------------------
+function M.nonempty(primary)
+ local p = M.make_parser('non-empty list', { primary = primary, name=primary.name })
+ function p :parse (lx)
+ local fli = lx:lineinfo_right()
+ local content = self.primary (lx)
+ local lli = lx:lineinfo_left()
+ local li = content.lineinfo or { }
+ fli, lli = li.first or fli, li.last or lli
+ if #content == 0 then
+ M.parse_error (lx, "`%s' must not be empty.", self.name or "list")
+ else
+ return transform (content, self, fli, lli)
+ end
+ end
+ return p
+end
+
+local FUTURE_MT = { }
+function FUTURE_MT:__tostring() return "<Proxy parser module>" end
+function FUTURE_MT:__newindex(key, value) error "don't write in futures" end
+function FUTURE_MT :__index (parser_name)
+ return function(...)
+ local p, m = rawget(self, '__path'), self.__module
+ if p then for _, name in ipairs(p) do
+ m=rawget(m, name)
+ if not m then error ("Submodule '"..name.."' undefined") end
+ end end
+ local f = rawget(m, parser_name)
+ if not f then error ("Parser '"..parser_name.."' undefined") end
+ return f(...)
+ end
+end
+
+function M.future(module, ...)
+ checks('table')
+ local path = ... and {...}
+ if path then for _, x in ipairs(path) do
+ assert(type(x)=='string', "Bad future arg")
+ end end
+ local self = { __module = module,
+ __path = path }
+ return setmetatable(self, FUTURE_MT)
+end
+
+return M
projects / metalua.git / blobdiff