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authorBjörn Gustavsson <[email protected]>2017-01-10 14:44:00 +0100
committerBjörn Gustavsson <[email protected]>2017-01-10 14:46:05 +0100
commitfa04f8212d282ea1535c07683660de1a23565b0f (patch)
tree4366ec01e34fdbd3587c2e21320b83e4ffa57a18 /system/doc
parent953f57e3a86f3b714a634177e32f630b56a05240 (diff)
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Modernize section about list handling and list comprehensions
Diffstat (limited to 'system/doc')
-rw-r--r--system/doc/efficiency_guide/listhandling.xml16
1 files changed, 12 insertions, 4 deletions
diff --git a/system/doc/efficiency_guide/listhandling.xml b/system/doc/efficiency_guide/listhandling.xml
index 2ebc877820..ec258d7c2a 100644
--- a/system/doc/efficiency_guide/listhandling.xml
+++ b/system/doc/efficiency_guide/listhandling.xml
@@ -90,7 +90,7 @@ tail_recursive_fib(N, Current, Next, Fibs) ->
<p>Lists comprehensions still have a reputation for being slow.
They used to be implemented using funs, which used to be slow.</p>
- <p>In recent Erlang/OTP releases (including R12B), a list comprehension:</p>
+ <p>A list comprehension:</p>
<code type="erl"><![CDATA[
[Expr(E) || E <- List]]]></code>
@@ -102,7 +102,7 @@ tail_recursive_fib(N, Current, Next, Fibs) ->
[Expr(E)|'lc^0'(Tail, Expr)];
'lc^0'([], _Expr) -> [].</code>
- <p>In R12B, if the result of the list comprehension will <em>obviously</em>
+ <p>If the result of the list comprehension will <em>obviously</em>
not be used, a list will not be constructed. For example, in this code:</p>
<code type="erl"><![CDATA[
@@ -131,6 +131,14 @@ some_function(...),
'lc^0'(Tail, Expr);
'lc^0'([], _Expr) -> [].</code>
+ <p>The compiler also understands that assigning to '_' means that
+ the value will not used. Therefore, the code in the following example
+ will also be optimized:</p>
+
+ <code type="erl"><![CDATA[
+_ = [io:put_chars(E) || E <- List],
+ok.]]></code>
+
</section>
<section>
@@ -209,11 +217,11 @@ some_function(...),
<section>
<title>Recursive List Functions</title>
- <p>In Section 7.2, the following myth was exposed:
+ <p>In section about myths, the following myth was exposed:
<seealso marker="myths#tail_recursive">Tail-Recursive Functions
are Much Faster Than Recursive Functions</seealso>.</p>
- <p>To summarize, in R12B there is usually not much difference between
+ <p>There is usually not much difference between
a body-recursive list function and tail-recursive function that reverses
the list at the end. Therefore, concentrate on writing beautiful code
and forget about the performance of your list functions. In the