1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 // ASCII art shape renderer.
12 // Demonstrates traits, impls, operator overloading, non-copyable struct, unit testing.
13 // To run execute: rustc --test shapes.rs && ./shapes
15 // Rust's std library is tightly bound to the language itself so it is automatically linked in.
16 // However the extra library is designed to be optional (for code that must run on constrained
17 // environments like embedded devices or special environments like kernel code) so it must
18 // be explicitly linked in.
21 // Extern mod controls linkage. Use controls the visibility of names to modules that are
22 // already linked in. Using WriterUtil allows us to use the write_line method.
23 use std::io::WriterUtil;
28 // Represents a position on a canvas.
34 // Represents an offset on a canvas. (This has the same structure as a Point.
35 // but different semantics).
48 // Contains the information needed to do shape rendering via ASCII art.
53 priv lines: ~[~[char]],
55 // This struct can be quite large so we'll disable copying: developers need
56 // to either pass these structs around via borrowed pointers or move them.
59 impl Drop for AsciiArt {
63 // It's common to define a constructor sort of function to create struct instances.
64 // If there is a canonical constructor it is typically named the same as the type.
65 // Other constructor sort of functions are typically named from_foo, from_bar, etc.
66 fn AsciiArt(width: uint, height: uint, fill: char) -> AsciiArt {
67 // Use an anonymous function to build a vector of vectors containing
68 // blank characters for each position in our canvas.
69 let lines = do vec::build(Some(height)) |push| {
71 push(vec::from_elem(width, '.'));
75 // Rust code often returns values by omitting the trailing semi-colon
76 // instead of using an explicit return statement.
77 AsciiArt {width: width, height: height, fill: fill, lines: lines}
80 // Methods particular to the AsciiArt struct.
82 fn add_pt(&mut self, x: int, y: int) {
83 if x >= 0 && x < self.width as int {
84 if y >= 0 && y < self.height as int {
85 // Note that numeric types don't implicitly convert to each other.
89 // Vector subscripting will normally copy the element, but &v[i]
90 // will return a reference which is what we need because the
92 // 1) potentially large
93 // 2) needs to be modified
94 let row = &mut self.lines[v];
101 // Allows AsciiArt to be converted to a string using the libcore ToStr trait.
102 // Note that the %s fmt! specifier will not call this automatically.
103 impl ToStr for AsciiArt {
104 fn to_str(&self) -> ~str {
105 // Convert each line into a string.
106 let lines = do self.lines.map |line| {str::from_chars(*line)};
108 // Concatenate the lines together using a new-line.
113 // This is similar to an interface in other languages: it defines a protocol which
114 // developers can implement for arbitrary concrete types.
116 fn add_point(&mut self, shape: Point);
117 fn add_rect(&mut self, shape: Rect);
119 // Unlike interfaces traits support default implementations.
120 // Got an ICE as soon as I added this method.
121 fn add_points(&mut self, shapes: &[Point]) {
122 for pt in shapes.iter() {self.add_point(*pt)};
126 // Here we provide an implementation of the Canvas methods for AsciiArt.
127 // Other implementations could also be provided (e.g. for PDF or Apple's Quartz)
128 // and code can use them polymorphically via the Canvas trait.
129 impl Canvas for AsciiArt {
130 fn add_point(&mut self, shape: Point) {
131 self.add_pt(shape.x, shape.y);
134 fn add_rect(&mut self, shape: Rect) {
135 // Add the top and bottom lines.
136 for x in range(shape.top_left.x, shape.top_left.x + shape.size.width) {
137 self.add_pt(x, shape.top_left.y);
138 self.add_pt(x, shape.top_left.y + shape.size.height - 1);
141 // Add the left and right lines.
142 for y in range(shape.top_left.y, shape.top_left.y + shape.size.height) {
143 self.add_pt(shape.top_left.x, y);
144 self.add_pt(shape.top_left.x + shape.size.width - 1, y);
149 // Rust's unit testing framework is currently a bit under-developed so we'll use
150 // this little helper.
151 pub fn check_strs(actual: &str, expected: &str) -> bool {
152 if actual != expected {
153 io::stderr().write_line(fmt!("Found:\n%s\nbut expected\n%s", actual, expected));
160 fn test_ascii_art_ctor() {
161 let art = AsciiArt(3, 3, '*');
162 assert!(check_strs(art.to_str(), "...\n...\n..."));
167 let mut art = AsciiArt(3, 3, '*');
171 assert!(check_strs(art.to_str(), "*..\n...\n.*."));
176 let mut art = AsciiArt(4, 4, '*');
177 art.add_rect(Rect {top_left: Point {x: 0, y: 0}, size: Size {width: 4, height: 4}});
178 art.add_point(Point {x: 2, y: 2});
179 assert!(check_strs(art.to_str(), "****\n*..*\n*.**\n****"));
183 test_ascii_art_ctor();