commit fecbccd73db52b9b15ddf3fb29d2b42457995b5d
parent fc57f5e766d5f7eb0600547dd7a0e3c6df7dd0ed
Author: Taylan Ulrich Bayırlı/Kammer <taylanbayirli@gmail.com>
Date: Sat, 15 Aug 2015 14:34:27 +0200
Fix ref specification.
Diffstat:
2 files changed, 26 insertions(+), 8 deletions(-)
diff --git a/README.md b/README.md
@@ -149,16 +149,27 @@ Specification
- `(ref object field)` (procedure)
- `(ref object field default)`
-Returns the value for `field` in `object`. If `object` is of a
-"sparse" type, meaning its fields can be "empty" or "unassigned"
-(e.g. a hashtable), and the requested field is empty, then the value
-of `default` is returned if given, and otherwise an error raised. If
-`object` is not of a sparse type, then `default` is ignored and an
-error raised if object doesn't have a value for `field`. (This error
-will typically come from the underlying accessor procedure.)
+Returns the value for `field` in `object`. An error is raised if
+`object` has no field identified by `field`. (This error will often
+come from the underlying accessor procedure.)
(ref #(0 1 2) 3) ;error: vector-ref: Index out of bounds.
+If `object` is of a "sparse" type, meaning its fields can be "empty"
+or "unassigned" (e.g. a hashtable), and the requested field is empty,
+then the value of `default` is returned if given, and otherwise an
+error raised.
+
+ (ref hashtable unassigned-key 'default) ;=> default
+ (ref hashtable unassigned-key) ;error
+
+If `object` is not of a sparse type, then passing `default` is an
+error.
+
+ (ref '(0 1 2) 3 'default) ;error: list-ref: Too many arguments.
+ ;Unless the implementation's list-ref
+ ;does something else.
+
Valid types for `object` are: bytevectors, hashtables, pairs, strings,
vectors, and all record types. Only hashtables are a sparse type.
Implementations are encouraged to expand this list of types with any
diff --git a/SRFI.html b/SRFI.html
@@ -66,8 +66,15 @@
<li><code>(ref object field)</code> (procedure)</li>
<li><code>(ref object field default)</code></li>
</ul>
-<p>Returns the value for <code>field</code> in <code>object</code>. If <code>object</code> is of a "sparse" type, meaning its fields can be "empty" or "unassigned" (e.g. a hashtable), and the requested field is empty, then the value of <code>default</code> is returned if given, and otherwise an error raised. If <code>object</code> is not of a sparse type, then <code>default</code> is ignored and an error raised if object doesn't have a value for <code>field</code>. (This error will typically come from the underlying accessor procedure.)</p>
+<p>Returns the value for <code>field</code> in <code>object</code>. An error is raised if <code>object</code> has no field identified by <code>field</code>. (This error will often come from the underlying accessor procedure.)</p>
<pre><code>(ref #(0 1 2) 3) ;error: vector-ref: Index out of bounds.</code></pre>
+<p>If <code>object</code> is of a "sparse" type, meaning its fields can be "empty" or "unassigned" (e.g. a hashtable), and the requested field is empty, then the value of <code>default</code> is returned if given, and otherwise an error raised.</p>
+<pre><code>(ref hashtable unassigned-key 'default) ;=> default
+(ref hashtable unassigned-key) ;error</code></pre>
+<p>If <code>object</code> is not of a sparse type, then passing <code>default</code> is an error.</p>
+<pre><code>(ref '(0 1 2) 3 'default) ;error: list-ref: Too many arguments.
+ ;Unless the implementation's list-ref
+ ;does something else.</code></pre>
<p>Valid types for <code>object</code> are: bytevectors, hashtables, pairs, strings, vectors, and all record types. Only hashtables are a sparse type. Implementations are encouraged to expand this list of types with any non-standard types they support.</p>
<p>Valid types for <code>field</code> depend on the type of <code>object</code>. For bytevectors, hashtables, strings, and vectors, refer to their respective <code>*-ref</code> procedures. For pairs, refer to <code>list-ref</code>. For records, symbols that correspond with the record type's field names are allowed.</p>
<p>If SRFI-17 is supported, then the <code>ref</code> procedure has the following setter: <code>(lambda (object field value) (set! object field value))</code></p>
