137 lines
10 KiB
HTML
137 lines
10 KiB
HTML
|
<html><head>
|
||
|
|
<style type="text/css">
|
||
|
|
body {color: #000; background-color: #FFFFF8;}
|
||
|
|
div#menu {font-size: smaller; position: absolute; top: 50px; left: 0; width: 250px; height: 100%}
|
||
|
|
div#menu a:link {text-decoration: none}
|
||
|
|
div#main {font-size: large; position: absolute; top: 0; left: 260px; max-width: 590px; height: 100%}
|
||
|
|
div#notes {position: relative; top: 2em; left: 620px; width: 200px; height: 0px; font-size: smaller;}
|
||
|
|
div#footer {padding-bottom: 50px}
|
||
|
|
div#menu ol {list-style-position:inside; padding-left: 5px; margin-left: 5px}
|
||
|
|
div#menu ol ol {list-style: lower-alpha; padding-left: 15px; margin-left: 15px}
|
||
|
|
div#menu ol ol ol {list-style: decimal; padding-left: 5px; margin-left: 5px}
|
||
|
|
h2 { color: #888888; border-top: 3px solid #4588ba; }
|
||
|
|
h3 { color: #666666; border-top: 2px solid #4588ba; }
|
||
|
|
h4 { color: #222288; border-top: 1px solid #4588ba; }
|
||
|
|
.result { color: #000; background-color: #FFEADF; width: 100%; padding: 3px}
|
||
|
|
.output { color: #000; background-color: beige; width: 100%; padding: 3px}
|
||
|
|
.error { color: #000; background-color: #F0B0B0; width: 100%; padding: 3px}
|
||
|
|
.command { color: #000; background-color: #FFEADF; width: 100%; padding: 5px}
|
||
|
|
.keyword { color: #800080; background-color: inherit; }
|
||
|
|
.type { color: #008000; background-color: inherit; }
|
||
|
|
.function { color: #0000FF; background-color: inherit; }
|
||
|
|
.variable { color: #B8860B; background-color: inherit; }
|
||
|
|
.comment { color: #FF0000; background-color: inherit; }
|
||
|
|
.string { color: #BC8F8F; background-color: inherit; }
|
||
|
|
.attribute { color: #FF5000; background-color: inherit; }
|
||
|
|
.preprocessor { color: #FF00FF; background-color: inherit; }
|
||
|
|
.builtin { color: #FF00FF; background-color: inherit; }
|
||
|
|
.character { color: #0055AA; background-color: inherit; }
|
||
|
|
.syntaxerror { color: #FF0000; background-color: inherit; }
|
||
|
|
.diff-deleted { color: #5F2121; background-color: inherit; }
|
||
|
|
.diff-added { color: #215F21; background-color: inherit; }
|
||
|
|
span.paren1 { color: #AAAAAA; background-color: inherit; }
|
||
|
|
span.paren2 { color: #888888; background-color: inherit; }
|
||
|
|
span.paren3 { color: #666666; background-color: inherit; }
|
||
|
|
span.paren4 { color: #444444; background-color: inherit; }
|
||
|
|
span.paren5 { color: #222222; background-color: inherit; }
|
||
|
|
span.paren6 { color: #000000; background-color: inherit; }
|
||
|
|
</style>
|
||
|
|
</head><body><div id="menu"><ol><li><a href="#h4_(let-optionalsls((vardefault)...[rest])body...)">let-optionals</a></li><li><a href="#h4_(let-optionals*ls((vardefault)...[rest])body...)">let-optionals*</a></li><li><a href="#h4_(opt-lambda((vardefault)...[rest])body...)">opt-lambda</a></li><li><a href="#h4_(define-opt(name(vardefault)...[rest])body...)">define-opt</a></li><li><a href="#h4_(keyword-reflskey[default])">keyword-ref</a></li><li><a href="#h4_(keyword-ref*lskeydefault)">keyword-ref*</a></li><li><a href="#h4_(let-keywordsls((var[keyword]default)...[rest])body...)">let-keywords</a></li><li><a href="#h4_(let-keywords*ls((var[keyword]default)...[rest])body...)">let-keywords*</a></li></ol></div><div id="main"><div><a name="h1_(chibioptional)"></a><h1>(chibi optional)</h1></div><p>Syntax to support optional and named keyword arguments.
|
||
|
|
<code><span>let-optionals</span>[<span>*</span>]</code> is originally from SCSH, and
|
||
|
|
<code><span>let-keywords</span>[<span>*</span>]</code> derived from Gauche.<div><a name="h4_(let-optionalsls((vardefault)...[rest])body...)"></a><h4><code>(let-optionals ls ((var default) ... [rest]) body ...)</code></h4></div>
|
||
|
|
|
||
|
|
Binding construct similar to <code><span>let</span></code>. The <code>var</code>s are
|
||
|
|
bound to fresh locations holding values taken in order from the
|
||
|
|
list <code>ls</code>, <code>body</code> is evaluated in the resulting
|
||
|
|
environment, and the value(s) of the last expression of <code>body</code>
|
||
|
|
returned. If the length of <code>ls</code> is shorter than the number of
|
||
|
|
<code>var</code>s, then the remaining <code>var</code>s taken their values from
|
||
|
|
their corresponding <code>default</code>s, evaluated in an unspecified
|
||
|
|
order. Unused <code>default</code>s are not evaluated. If a final
|
||
|
|
<code>rest</code> var is specified, then it is bound to any remaining
|
||
|
|
elements of <code>ls</code> beyond the length of <code>ls</code>, otherwise any
|
||
|
|
extra values are unused.
|
||
|
|
|
||
|
|
Typically used on the dotted rest list at the start of a lambda,
|
||
|
|
<code><span>let-optionals</span></code> is more concise and more efficient than
|
||
|
|
<code><span>case-lambda</span></code> for simple optional argument uses.
|
||
|
|
|
||
|
|
<em>Example:</em>
|
||
|
|
<pre><code>(<span class="keyword">define</span> (<span class="function">copy-port</span> <span>.</span> <span>o</span>)
|
||
|
|
(<span class="keyword">let-optionals</span> <span>o</span> ((in (current-input-port))
|
||
|
|
(out (current-output-port))
|
||
|
|
(n-bytes #f))
|
||
|
|
(<span class="keyword">do</span> ((i <span>0</span> (+ <span>i</span> <span>1</span>))
|
||
|
|
(n (read-u8 <span>in</span>) (read-u8 <span>in</span>)))
|
||
|
|
((or (and <span>n-bytes</span> (>= <span>i</span> <span>n-bytes</span>))
|
||
|
|
(eof-object? <span>b</span>)))
|
||
|
|
(write-u8 <span>b</span> <span>out</span>)))</code></pre>
|
||
|
|
|
||
|
|
<em>Example:</em>
|
||
|
|
<div><pre><code>(<span class="keyword">let-optionals</span> '(0) ((a <span>10</span>) (b <span>11</span>) (c <span>12</span>))
|
||
|
|
(list <span>a</span> <span>b</span> <span>c</span>))</code></pre><div class="result"><code>=> (0 11 12)</code></div></div><div><a name="h4_(let-optionals*ls((vardefault)...[rest])body...)"></a><h4><code>(let-optionals* ls ((var default) ... [rest]) body ...)</code></h4></div>
|
||
|
|
|
||
|
|
<code><span>let*</span></code> equivalent to <code><span>let-optionals</span></code>. Any required
|
||
|
|
<code>default</code> values are evaluated in left-to-right order, with
|
||
|
|
all preceding <code>var</code>s in scope.
|
||
|
|
<div><a name="h4_(opt-lambda((vardefault)...[rest])body...)"></a><h4><code>(opt-lambda ((var default) ... [rest]) body ...)</code></h4></div>
|
||
|
|
|
||
|
|
Shorthand for
|
||
|
|
<pre><code>(<span class="keyword">lambda</span> (required <span>...</span> <span>.</span> <span>o</span>)
|
||
|
|
(<span class="keyword">let-optionals</span> <span>o</span> ((var <span>default</span>) <span>...</span> [<span>rest</span>])
|
||
|
|
<span>body</span> <span>...</span>))</code></pre><div><a name="h4_(define-opt(name(vardefault)...[rest])body...)"></a><h4><code>(define-opt (name (var default) ... [rest]) body ...)</code></h4></div>
|
||
|
|
|
||
|
|
Shorthand for
|
||
|
|
<pre><code>(<span class="keyword">define</span> <span class="function">name</span> (opt-lambda (var <span>default</span>) <span>...</span> [<span>rest</span>]) <span>body</span> <span>...</span>)</code></pre><div><a name="h4_(keyword-reflskey[default])"></a><h4><code>(keyword-ref ls key [default])</code></h4></div>
|
||
|
|
|
||
|
|
Search for the identifier <code>key</code> in the list <code>ls</code>, treating
|
||
|
|
it as a property list of the form <code>(key1 <span>val1</span> <span>key2</span> <span>val2</span>
|
||
|
|
<span>...</span>)</code>, and return the associated <code>val</code>. If not found, return
|
||
|
|
<code>default</code>, or <code>#f</code>.<div><a name="h4_(keyword-ref*lskeydefault)"></a><h4><code>(keyword-ref* ls key default)</code></h4></div>
|
||
|
|
|
||
|
|
Macro equivalent of <code><span>keyword-ref</span></code>, where <code>default</code> is
|
||
|
|
only evaluated if <code>key</code> is not found.<div><a name="h4_(let-keywordsls((var[keyword]default)...[rest])body...)"></a><h4><code>(let-keywords ls ((var [keyword] default) ... [rest]) body ...)</code></h4></div>
|
||
|
|
|
||
|
|
Analogous to <code><span>let-optionals</span></code>, except instead of binding the
|
||
|
|
<code>var</code>s by position they are bound by name, by searching in
|
||
|
|
<code>ls</code> with <code><span>keyword-ref*</span></code>. If an optional <code>keyword</code>
|
||
|
|
argument is provided it must be an identifier to use as the name,
|
||
|
|
otherwise <code>var</code> is used, appending a ":" (colon). If the name
|
||
|
|
is not found, <code>var</code> is bound to <code>default</code>, even if unused
|
||
|
|
names remain in <code>ls</code>.
|
||
|
|
|
||
|
|
If an optional trailing identifier <code>rest</code> is provided, it is
|
||
|
|
bound to the list of unused arguments not bound to any <code>var</code>.
|
||
|
|
|
||
|
|
Note R7RS does not have a disjoint keyword type or auto-quoting
|
||
|
|
syntax for keywords - they are simply identifiers. Thus when
|
||
|
|
passing keyword arguments they must be quoted (or otherwise
|
||
|
|
dynamically evaluated).
|
||
|
|
|
||
|
|
<em>Example:</em>
|
||
|
|
<div><pre><code>(<span class="keyword">define</span> (<span class="function">make-person</span> <span>.</span> <span>o</span>)
|
||
|
|
(<span class="keyword">let-keywords</span> <span>o</span> ((name <span class="string">"John Doe"</span>)
|
||
|
|
(age <span>0</span>)
|
||
|
|
(occupation <span>job:</span> '<span>unemployed</span>))
|
||
|
|
(vector <span>name</span> <span>age</span> <span>occupation</span>))<span class="syntaxerror">)</span>
|
||
|
|
|
||
|
|
(list (make-person)
|
||
|
|
(make-person '<span>name:</span> <span class="string">"Methuselah"</span> '<span>age:</span> <span>969</span>)
|
||
|
|
(make-person '<span>name:</span> <span class="string">"Dr. Who"</span> '<span>job:</span> '<span>time-lord</span> '<span>age:</span> <span>1500</span>))
|
||
|
|
</code></pre><div class="result"><code>=> (#("John Doe" 0 unemployed) #("Methuselah" 969 unemployed) #("Dr. Who" 1500 time-lord))</code></div></div>
|
||
|
|
|
||
|
|
<em>Example:</em>
|
||
|
|
<div><pre><code>(<span class="keyword">let-keywords</span> '(b: <span>2</span> <span>a:</span> <span>1</span> <span>other:</span> <span>9</span>)
|
||
|
|
((a <span>0</span>) (b <span>0</span>) (c <span>0</span>) <span>rest</span>)
|
||
|
|
(list <span>a</span> <span>b</span> <span>c</span> <span>rest</span>))
|
||
|
|
</code></pre><div class="result"><code>=> (1 2 0 (other: 9))</code></div></div><div><a name="h4_(let-keywords*ls((var[keyword]default)...[rest])body...)"></a><h4><code>(let-keywords* ls ((var [keyword] default) ... [rest]) body ...)</code></h4></div>
|
||
|
|
|
||
|
|
<code><span>let*</span></code> equivalent to <code><span>let-keywords*</span></code>. Any required
|
||
|
|
<code>default</code> values are evaluated in left-to-right order, with
|
||
|
|
all preceding <code>var</code>s in scope.
|
||
|
|
|
||
|
|
<em>Example:</em>
|
||
|
|
<div><pre><code>(<span class="keyword">let-keywords*</span> '(b: <span>5</span>)
|
||
|
|
((a <span>1</span>) (b (* <span>a</span> <span>2</span>)) (c (* <span>b</span> <span>3</span>)))
|
||
|
|
(list <span>a</span> <span>b</span> <span>c</span>))
|
||
|
|
</code></pre><div class="result"><code>=> (1 5 15)</code></div></div></p><div id="footer"></div></div></body></html>
|