Merge pull request #1280 from bjorng/bjorn/effiency-guide-myths/OTP-13652

Update the myths in the Efficiency Guide for OTP 20

1 files changed, 63 insertions, 0 deletions

diff --git a/system/doc/efficiency_guide/retired_myths.xml b/system/doc/efficiency_guide/retired_myths.xml
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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>