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documentation for pattern matching

This commit is contained in:
Jeremy Ashkenas 2010-01-11 22:55:01 -05:00
parent 186797a745
commit c3029faca7
8 changed files with 202 additions and 16 deletions
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5
documentation/coffee/multiple_return_values.coffee Normal file
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@ -0,0 +1,5 @@
weather_report: location =>
# Make an Ajax request to fetch the weather...
[location, 72, "Mostly Sunny"]
[city, temp, forecast]: weather_report("Berkeley, CA")

13
documentation/coffee/object_extraction.coffee Normal file
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@ -0,0 +1,13 @@
futurists: {
sculptor: "Umberto Boccioni"
painter: "Vladimir Burliuk"
poet: {
name: "F.T. Marinetti"
address: [
"Via Roma 42R"
"Bellagio, Italy 22021"
]
}
}
{poet: {name: poet, address: [street, city]}}: futurists

4
documentation/coffee/parallel_assignment.coffee Normal file
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@ -0,0 +1,4 @@
bait: 1000
and_switch: 0
[bait, and_switch]: [and_switch, bait]

39
documentation/index.html.erb
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@ -75,6 +75,7 @@
<a href="#expressions">Everything is an Expression</a><br />
<a href="#inheritance">Inheritance, and Calling Super from a Subclass</a><br />
<a href="#blocks">Blocks</a><br />
<a href="#pattern_matching">Pattern Matching</a><br />
<a href="#embedded">Embedded JavaScript</a><br />
<a href="#switch">Switch/When/Else</a><br />
<a href="#try">Try/Catch/Finally</a><br />
@ -95,7 +96,7 @@
<a href="documentation/underscore.html">Underscore.coffee</a>, a port
of the <a href="http://documentcloud.github.com/underscore/">Underscore.js</a>
library of helper functions. Underscore.coffee can pass the entire Underscore.js
test suite. The CoffeeScript version is faster than the original for a number
test suite. The CoffeeScript version is faster than the original for a number
of methods (in general, due to the speed of CoffeeScript's array comprehensions), and
after being minified and gzipped, is only 241 bytes larger than the original
JavaScript version.
@ -415,7 +416,7 @@ coffee --print app/scripts/*.coffee > concatenation.js</pre>
<%= code_for('range_comprehensions', 'countdown') %>
<p>
Comprehensions can also be used to iterate over the keys and values in
an object. Use <tt>of</tt> to signal comprehension over the properties of
an object. Use <tt>of</tt> to signal comprehension over the properties of
an object instead of the values in an array.
</p>
<%= code_for('object_comprehensions', 'ages.join(", ")') %>
@ -481,12 +482,12 @@ coffee --print app/scripts/*.coffee > concatenation.js</pre>
be completely usable if it weren't for a couple of small exceptions:
it's awkward to call <b>super</b> (the prototype object's
implementation of the current function), and it's awkward to correctly
set the prototype chain.
set the prototype chain.
</p>
<p>
CoffeeScript provides <tt>extends</tt>
to help with prototype setup, <tt>::</tt> for quick access to an
object's prototype, and converts <tt>super()</tt> into a call against
object's prototype, and converts <tt>super()</tt> into a call against
the immediate ancestor's method of the same name.
</p>
<%= code_for('super', true) %>
@ -500,14 +501,36 @@ coffee --print app/scripts/*.coffee > concatenation.js</pre>
</p>
<%= code_for('blocks') %>
<p>
If you prefer not to use blocks, you'll need to add a pair of parentheses
If you prefer not to use blocks, you'll need to add a pair of parentheses
to help distinguish the arguments from the definition of the function:
<tt>_.map(array, (num => num * 2))</tt>
</p>
<p id="pattern_matching">
<b class="header">Pattern Matching (Destructuring Assignment)</b>
To make working with complex arrays and objects more convenient,
CoffeeScript provides ECMAScript Harmony's proposed
<a href="http://wiki.ecmascript.org/doku.php?id=harmony:destructuring">destructuring assignment</a>
syntax. When you assign an array or object literal to a value, CoffeeScript
breaks up and matches both sides against each other, assigning the values
on the right to the variables on the left. In the simplest case, it can be
used for parallel assignment:
</p>
<%= code_for('parallel_assignment', 'bait') %>
<p>
But it's also helpful for dealing with functions that return multiple
values.
</p>
<%= code_for('multiple_return_values', 'forecast') %>
<p>
Pattern matching can be used with any depth of array and object nesting,
to help cleanly extract deeply nested properties.
</p>
<%= code_for('object_extraction', 'poet + " — " + street') %>
<p id="embedded">
<b class="header">Embedded JavaScript</b>
Hopefully, you'll never need to use it, but if you ever need to intersperse
Hopefully, you'll never need to use it, but if you ever need to intersperse
snippets of JavaScript within your CoffeeScript, you can
use backticks to pass it straight through.
</p>
@ -545,7 +568,7 @@ coffee --print app/scripts/*.coffee > concatenation.js</pre>
<a href="http://github.com/jashkenas/coffee-script/">Source Code</a><br />
After checking out the source, make sure to run <tt>rake build:parser</tt>
to generate an up-to-date version of the Racc parser.
Use <tt>bin/coffee</tt> to test your changes,
Use <tt>bin/coffee</tt> to test your changes,
<tt>rake test</tt> to run the test suite,
and <tt>rake gem:install</tt> to
create and install a custom version of the gem.
@ -594,7 +617,7 @@ coffee --print app/scripts/*.coffee > concatenation.js</pre>
</ul>
<h2 id="change_log">Change Log</h2>
<p>
<b class="header" style="margin-top: 20px;">0.2.3</b>
Axed the unsatisfactory <tt>ino</tt> keyword, replacing it with <tt>of</tt> for

11
documentation/js/multiple_return_values.js Normal file
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@ -0,0 +1,11 @@
(function(){
var __a, city, forecast, temp, weather_report;
weather_report = function weather_report(location) {
// Make an Ajax request to fetch the weather...
return [location, 72, "Mostly Sunny"];
};
__a = weather_report("Berkeley, CA");
city = __a[0];
temp = __a[1];
forecast = __a[2];
})();

17
documentation/js/object_extraction.js Normal file
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@ -0,0 +1,17 @@
(function(){
var __a, __b, __c, city, futurists, poet, street;
futurists = {
sculptor: "Umberto Boccioni",
painter: "Vladimir Burliuk",
poet: {
name: "F.T. Marinetti",
address: ["Via Roma 42R", "Bellagio, Italy 22021"]
}
};
__a = futurists;
__b = __a.poet;
poet = __b.name;
__c = __b.address;
street = __c[0];
city = __c[1];
})();

8
documentation/js/parallel_assignment.js Normal file
View File

@ -0,0 +1,8 @@
(function(){
var __a, and_switch, bait;
bait = 1000;
and_switch = 0;
__a = [and_switch, bait];
bait = __a[0];
and_switch = __a[1];
})();

121
index.html
View File

@ -61,6 +61,7 @@
<a href="#expressions">Everything is an Expression</a><br />
<a href="#inheritance">Inheritance, and Calling Super from a Subclass</a><br />
<a href="#blocks">Blocks</a><br />
<a href="#pattern_matching">Pattern Matching</a><br />
<a href="#embedded">Embedded JavaScript</a><br />
<a href="#switch">Switch/When/Else</a><br />
<a href="#try">Try/Catch/Finally</a><br />
@ -192,7 +193,7 @@ cubed_list = (function() {
<a href="documentation/underscore.html">Underscore.coffee</a>, a port
of the <a href="http://documentcloud.github.com/underscore/">Underscore.js</a>
library of helper functions. Underscore.coffee can pass the entire Underscore.js
test suite. The CoffeeScript version is faster than the original for a number
test suite. The CoffeeScript version is faster than the original for a number
of methods (in general, due to the speed of CoffeeScript's array comprehensions), and
after being minified and gzipped, is only 241 bytes larger than the original
JavaScript version.
@ -782,7 +783,7 @@ egg_delivery = function egg_delivery() {
;alert(countdown);'>run: countdown</button><br class='clear' /></div>
<p>
Comprehensions can also be used to iterate over the keys and values in
an object. Use <tt>of</tt> to signal comprehension over the properties of
an object. Use <tt>of</tt> to signal comprehension over the properties of
an object instead of the values in an array.
</p>
<div class='code'><pre class="idle"><span class="FunctionName">years_old</span><span class="Keyword">:</span> {<span class="FunctionName">max</span><span class="Keyword">:</span> <span class="Number">10</span>, <span class="FunctionName">ida</span><span class="Keyword">:</span> <span class="Number">9</span>, <span class="FunctionName">tim</span><span class="Keyword">:</span> <span class="Number">11</span>}
@ -990,12 +991,12 @@ globals = ((function() {
be completely usable if it weren't for a couple of small exceptions:
it's awkward to call <b>super</b> (the prototype object's
implementation of the current function), and it's awkward to correctly
set the prototype chain.
set the prototype chain.
</p>
<p>
CoffeeScript provides <tt>extends</tt>
to help with prototype setup, <tt>::</tt> for quick access to an
object's prototype, and converts <tt>super()</tt> into a call against
object's prototype, and converts <tt>super()</tt> into a call against
the immediate ancestor's method of the same name.
</p>
<div class='code'><pre class="idle"><span class="FunctionName">Animal</span><span class="Keyword">:</span> <span class="Storage">=&gt;</span>
@ -1120,14 +1121,118 @@ tom.move();
});
</pre><br class='clear' /></div>
<p>
If you prefer not to use blocks, you'll need to add a pair of parentheses
If you prefer not to use blocks, you'll need to add a pair of parentheses
to help distinguish the arguments from the definition of the function:
<tt>_.map(array, (num => num * 2))</tt>
</p>
<p id="pattern_matching">
<b class="header">Pattern Matching (Destructuring Assignment)</b>
To make working with complex arrays and objects more convenient,
CoffeeScript provides ECMAScript Harmony's proposed
<a href="http://wiki.ecmascript.org/doku.php?id=harmony:destructuring">destructuring assignment</a>
syntax. When you assign an array or object literal to a value, CoffeeScript
breaks up and matches both sides against each other, assigning the values
on the right to the variables on the left. In the simplest case, it can be
used for parallel assignment:
</p>
<div class='code'><pre class="idle"><span class="FunctionName">bait</span><span class="Keyword">:</span> <span class="Number">1000</span>
<span class="FunctionName">and_switch</span><span class="Keyword">:</span> <span class="Number">0</span>
[bait, and_switch]<span class="Keyword">:</span> [and_switch, bait]
</pre><pre class="idle"><span class="Storage">var</span> __a, and_switch, bait;
bait <span class="Keyword">=</span> <span class="Number">1000</span>;
and_switch <span class="Keyword">=</span> <span class="Number">0</span>;
__a <span class="Keyword">=</span> [and_switch, bait];
bait <span class="Keyword">=</span> __a[<span class="Number">0</span>];
and_switch <span class="Keyword">=</span> __a[<span class="Number">1</span>];
</pre><button onclick='javascript: var __a, and_switch, bait;
bait = 1000;
and_switch = 0;
__a = [and_switch, bait];
bait = __a[0];
and_switch = __a[1];
;alert(bait);'>run: bait</button><br class='clear' /></div>
<p>
But it's also helpful for dealing with functions that return multiple
values.
</p>
<div class='code'><pre class="idle"><span class="FunctionName">weather_report</span><span class="Keyword">:</span> <span class="FunctionArgument">location</span> <span class="Storage">=&gt;</span>
<span class="Comment"><span class="Comment">#</span> Make an Ajax request to fetch the weather...</span>
[location, <span class="Number">72</span>, <span class="String"><span class="String">&quot;</span>Mostly Sunny<span class="String">&quot;</span></span>]
[city, temp, forecast]<span class="Keyword">:</span> weather_report(<span class="String"><span class="String">&quot;</span>Berkeley, CA<span class="String">&quot;</span></span>)
</pre><pre class="idle"><span class="Storage">var</span> __a, city, forecast, temp, weather_report;
weather_report <span class="Keyword">=</span> <span class="Storage">function</span> <span class="FunctionName">weather_report</span>(<span class="FunctionArgument">location</span>) {
<span class="Comment"><span class="Comment">//</span> Make an Ajax request to fetch the weather...</span>
<span class="Keyword">return</span> [location, <span class="Number">72</span>, <span class="String"><span class="String">&quot;</span>Mostly Sunny<span class="String">&quot;</span></span>];
};
__a <span class="Keyword">=</span> weather_report(<span class="String"><span class="String">&quot;</span>Berkeley, CA<span class="String">&quot;</span></span>);
city <span class="Keyword">=</span> __a[<span class="Number">0</span>];
temp <span class="Keyword">=</span> __a[<span class="Number">1</span>];
forecast <span class="Keyword">=</span> __a[<span class="Number">2</span>];
</pre><button onclick='javascript: var __a, city, forecast, temp, weather_report;
weather_report = function weather_report(location) {
// Make an Ajax request to fetch the weather...
return [location, 72, "Mostly Sunny"];
};
__a = weather_report("Berkeley, CA");
city = __a[0];
temp = __a[1];
forecast = __a[2];
;alert(forecast);'>run: forecast</button><br class='clear' /></div>
<p>
Pattern matching can be used with any depth of array and object nesting,
to help cleanly extract deeply nested properties.
</p>
<div class='code'><pre class="idle"><span class="FunctionName">futurists</span><span class="Keyword">:</span> {
<span class="FunctionName">sculptor</span><span class="Keyword">:</span> <span class="String"><span class="String">&quot;</span>Umberto Boccioni<span class="String">&quot;</span></span>
<span class="FunctionName">painter</span><span class="Keyword">:</span> <span class="String"><span class="String">&quot;</span>Vladimir Burliuk<span class="String">&quot;</span></span>
<span class="FunctionName">poet</span><span class="Keyword">:</span> {
<span class="FunctionName">name</span><span class="Keyword">:</span> <span class="String"><span class="String">&quot;</span>F.T. Marinetti<span class="String">&quot;</span></span>
<span class="FunctionName">address</span><span class="Keyword">:</span> [
<span class="String"><span class="String">&quot;</span>Via Roma 42R<span class="String">&quot;</span></span>
<span class="String"><span class="String">&quot;</span>Bellagio, Italy 22021<span class="String">&quot;</span></span>
]
}
}
{<span class="FunctionName">poet</span><span class="Keyword">:</span> {<span class="FunctionName">name</span><span class="Keyword">:</span> poet, <span class="FunctionName">address</span><span class="Keyword">:</span> [street, city]}}<span class="Keyword">:</span> futurists
</pre><pre class="idle"><span class="Storage">var</span> __a, __b, __c, city, futurists, poet, street;
futurists <span class="Keyword">=</span> {
sculptor: <span class="String"><span class="String">&quot;</span>Umberto Boccioni<span class="String">&quot;</span></span>,
painter: <span class="String"><span class="String">&quot;</span>Vladimir Burliuk<span class="String">&quot;</span></span>,
poet: {
name: <span class="String"><span class="String">&quot;</span>F.T. Marinetti<span class="String">&quot;</span></span>,
address: [<span class="String"><span class="String">&quot;</span>Via Roma 42R<span class="String">&quot;</span></span>, <span class="String"><span class="String">&quot;</span>Bellagio, Italy 22021<span class="String">&quot;</span></span>]
}
};
__a <span class="Keyword">=</span> futurists;
__b <span class="Keyword">=</span> __a.poet;
poet <span class="Keyword">=</span> __b.<span class="LibraryConstant">name</span>;
__c <span class="Keyword">=</span> __b.address;
street <span class="Keyword">=</span> __c[<span class="Number">0</span>];
city <span class="Keyword">=</span> __c[<span class="Number">1</span>];
</pre><button onclick='javascript: var __a, __b, __c, city, futurists, poet, street;
futurists = {
sculptor: "Umberto Boccioni",
painter: "Vladimir Burliuk",
poet: {
name: "F.T. Marinetti",
address: ["Via Roma 42R", "Bellagio, Italy 22021"]
}
};
__a = futurists;
__b = __a.poet;
poet = __b.name;
__c = __b.address;
street = __c[0];
city = __c[1];
;alert(poet + " — " + street);'>run: poet + " — " + street</button><br class='clear' /></div>
<p id="embedded">
<b class="header">Embedded JavaScript</b>
Hopefully, you'll never need to use it, but if you ever need to intersperse
Hopefully, you'll never need to use it, but if you ever need to intersperse
snippets of JavaScript within your CoffeeScript, you can
use backticks to pass it straight through.
</p>
@ -1238,7 +1343,7 @@ world...";
<a href="http://github.com/jashkenas/coffee-script/">Source Code</a><br />
After checking out the source, make sure to run <tt>rake build:parser</tt>
to generate an up-to-date version of the Racc parser.
Use <tt>bin/coffee</tt> to test your changes,
Use <tt>bin/coffee</tt> to test your changes,
<tt>rake test</tt> to run the test suite,
and <tt>rake gem:install</tt> to
create and install a custom version of the gem.
@ -1287,7 +1392,7 @@ world...";
</ul>
<h2 id="change_log">Change Log</h2>
<p>
<b class="header" style="margin-top: 20px;">0.2.3</b>
Axed the unsatisfactory <tt>ino</tt> keyword, replacing it with <tt>of</tt> for