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authorBjörn Gustavsson <[email protected]>2016-06-07 15:14:16 +0200
committerBjörn Gustavsson <[email protected]>2016-12-15 10:13:46 +0100
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Retire two myths
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+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE chapter SYSTEM "chapter.dtd">
+
+<chapter>
+ <header>
+ <copyright>
+ <year>2016</year>
+ <year>2016</year>
+ <holder>Ericsson AB, All Rights Reserved</holder>
+ </copyright>
+ <legalnotice>
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+ The Initial Developer of the Original Code is Ericsson AB.
+ </legalnotice>
+ <marker id="retired_myths"/>
+ <title>Retired Myths</title>
+ <prepared>Bjorn Gustavsson</prepared>
+ <docno></docno>
+ <date>2016-06-07</date>
+ <rev></rev>
+ <file>retired_myths.xml</file>
+ </header>
+
+ <p>We belive that the truth finally has caught with the following,
+ retired myths.</p>
+
+ <section>
+ <title>Myth: Funs are Slow</title>
+ <p>Funs used to be very slow, slower than <c>apply/3</c>.
+ Originally, funs were implemented using nothing more than
+ compiler trickery, ordinary tuples, <c>apply/3</c>, and a great
+ deal of ingenuity.</p>
+
+ <p>But that is history. Funs was given its own data type
+ in R6B and was further optimized in R7B.
+ Now the cost for a fun call falls roughly between the cost for a call
+ to a local function and <c>apply/3</c>.</p>
+ </section>
+
+ <section>
+ <title>Myth: List Comprehensions are Slow</title>
+
+ <p>List comprehensions used to be implemented using funs, and in the
+ old days funs were indeed slow.</p>
+
+ <p>Nowadays, the compiler rewrites list comprehensions into an ordinary
+ recursive function. Using a tail-recursive function with
+ a reverse at the end would be still faster. Or would it?
+ That leads us to the myth that tail-recursive functions are faster
+ than body-recursive functions.</p>
+ </section>
+</chapter>