Lo que todo programador debería saber sobre aritmética de punto flotante
fixed issue #1: Added description meta header tag
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---
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title: Basic Answers
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description: Concise answers to common basic questions about floating-point math, like "Why don't my numbers add up?"
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---
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### Why don't my numbers, like 0.1 + 0.2 add up to a nice round 0.3, and instead I get a weird result like 0.30000000000000004?
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---
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title: Exact Types
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description: Description of various datatypes that can be more exact that floating-point numbers
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---
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While [binary](/formats/binary/) [floating-point](/formats/fp/) numbers are better for computers to work with, and usually good enough for humans, sometimes they are just not appropriate. Sometimes, the numbers really must add up to the last bit, and no technical excuses are acceptable - usually when the calculations involve money.
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---
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title: On Using Integers
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description: Explanation why using integers to avoid floating-point problems by having them represent e.g. cents is not a good solution.
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---
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While integer types are usually binary and by definition do not support fractions, they are exact (no [rounding errors](/errors/rounding/) when converting from decimal integers) and can be used as a sort of "poor man's [decimal type](/formats/exact/)" by choosing an implicit fixed decimal point so that the smallest unit you work with can be represented as the integer 1. In practical terms, this is often put as: **"To handle money, store and calculate everything in cents and format only the output"**.
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content/index.html
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---
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title: What Every Programmer Should Know About Floating-Point Arithmetic
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description: Aims to provide both short and simple answers to the common recurring questions of novice programmers about floating-point numbers not 'adding up' correctly, and more in-depth information about how IEEE 754 floats work, when and how to use them correctly, and what to use instead when they are not appropriate.
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verification: SoYmbsJEmSz2s1LmZk_cku4pKwhRsU6m0ZOTgGdnTL0
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---
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or
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---
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title: How to deal with floating-point numbers in Java
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description: Tips for using floating-point numbers in Java
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---
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Floating-Point Types
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Decimal Types
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-------------
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Java has an [arbitrary-precision](/formats/exact/) decimal type named <code>java.math.BigDecimal</code>, which
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also allows to choose the rounding mode:
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also allows to choose the rounding mode.
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BigDecimal a = new BigDecimal("0.1");
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BigDecimal b = new BigDecimal("0.2");
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BigDecimal c = a.add(b); // returns a BigDecimal representing exactly 0.3
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---
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title: xkcd
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description: How to mess with people who've learned to *expect* rounding errors in floating-point math.
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---
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or
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--
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How to mess with people who've learned to *expect* rounding errors in floating-point math.
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<%= @item[:description] %>
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====================
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<head>
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<meta charset="utf-8">
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<title>The Floating-Point Guide - <%= @item[:title] %></title>
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<meta name="google-site-verification" content="SoYmbsJEmSz2s1LmZk_cku4pKwhRsU6m0ZOTgGdnTL0" />
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<% if @item[:verification] %>
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<meta name="google-site-verification" content="SoYmbsJEmSz2s1LmZk_cku4pKwhRsU6m0ZOTgGdnTL0" />
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<% end %>
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<meta name="generator" content="nanoc 3.1.2">
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<% if @item[:description] %>
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<meta name="Description" content="<%= @item[:description] %>">
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<% end %>
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<link rel="stylesheet" type="text/css" href="/style.css" media="screen">
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<link rel="shortcut icon" href="/favicon.ico" type="image/vnd.microsoft.icon">
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</head>