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authorBjörn Gustavsson <bjorn@erlang.org>2010-04-09 15:50:17 +0200
committerBjörn Gustavsson <bjorn@erlang.org>2011-11-07 13:57:03 +0100
commitff432e262e65243cbc983fcb002527f8fae8c78b (patch)
tree1966b14f94663375eb0333c3e2d707aab501a960 /system/doc
parent33c08d87a9395ae088eebcad9fb62193d26b6846 (diff)
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EEP-23: Allow variables in fun M:F/A
Currently, the external fun syntax "fun M:F/A" only supports literals. That is, "fun lists:reverse/1" is allowed but not "fun M:F/A". In many real-life situations, some or all of M, F, A are not known until run-time, and one is forced to either use the undocumented erlang:make_fun/3 BIF or to use a "tuple fun" (which is deprecated). EEP-23 suggests that the parser (erl_parse) should immediately transform "fun M:F/A" to "erlang:make_fun(M, F, A)". We have not followed that approach in this implementation, because we want the abstract code to mirror the source code as closely as possible, and we also consider erlang:make_fun/3 to be an implementation detail that we might want to remove in the future. Instead, we will change the abstract format for "fun M:F/A" (in a way that is not backwards compatible), and while we are at it, we will move the translation from "fun M:F/A" to "erlang:make_fun(M, F, A)" from sys_pre_expand down to the v3_core pass. We will also update the debugger and xref to use the new format. We did consider making the abstract format backward compatible if no variables were used in the fun, but decided against it. Keeping it backward compatible would mean that there would be different abstract formats for the no-variable and variable case, and tools would have to handle both formats, probably forever. Reference: http://www.erlang.org/eeps/eep-0023.html
Diffstat (limited to 'system/doc')
-rw-r--r--system/doc/reference_manual/expressions.xml3
1 files changed, 2 insertions, 1 deletions
diff --git a/system/doc/reference_manual/expressions.xml b/system/doc/reference_manual/expressions.xml
index 4d211ae1d3..43d46d87cc 100644
--- a/system/doc/reference_manual/expressions.xml
+++ b/system/doc/reference_manual/expressions.xml
@@ -993,7 +993,8 @@ fun Module:Name/Arity</pre>
<pre>
fun (Arg1,...,ArgN) -> Name(Arg1,...,ArgN) end</pre>
<p>In <c>Module:Name/Arity</c>, <c>Module</c> and <c>Name</c> are atoms
- and <c>Arity</c> is an integer.
+ and <c>Arity</c> is an integer. Starting from the R15 release,
+ <c>Module</c>, <c>Name</c>, and <c>Arity</c> may also be variables.
A fun defined in this way will refer to the function <c>Name</c>
with arity <c>Arity</c> in the <em>latest</em> version of module
<c>Module</c>. A fun defined in this way will not be dependent on