Lo que todo programador debería saber sobre aritmética de punto flotante
added language details
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content/languages/csharp.html
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How to Round
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------------
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TODO
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The <code>Math.Round()</code> method works with the double and decimal types, and allows you to specify a [rounding mode](/errors/rounding/):
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Math.Round(1.25m, 1, MidpointRounding.AwayFromZero); // returns 1.3
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Resources
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content/languages/java.html
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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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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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also allows to choose the [rounding mode](/errors/rounding/).
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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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How to Round
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------------
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To get a String:
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String.format("%.2f", 1.2399) // returns "1.24"
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String.format("%.3f", 1.2399) // returns "1.240"
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String.format("%.2f", 1.2) // returns "1.20"
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String.format("%.2f", 1.2399) // returns "1.24"
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String.format("%.3f", 1.2399) // returns "1.240"
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String.format("%.2f", 1.2) // returns "1.20"
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To print to standard output (or any <code>PrintStream</code>):
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System.out.printf("%.2f", 1.2399) // same syntax as String.format()
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System.out.printf("%.2f", 1.2399) // same syntax as String.format()
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If you don't want trailing zeroes:
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new DecimalFormat("0.00").format(1.2)// returns "1.20"
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new DecimalFormat("0.##").format(1.2)// returns "1.2"
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new DecimalFormat("0.00").format(1.2)// returns "1.20"
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new DecimalFormat("0.##").format(1.2)// returns "1.2"
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If you need a specific [rounding mode](/errors/rounding/):
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new BigDecimal("1.25").setScale(1, RoundingMode.HALF_EVEN); // returns 1.2
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Resources
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content/languages/javascript.html
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Decimal Types
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-------------
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TODO: is there a standard or widely used JS bignum/decimal library?
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The best decimal type for JavaScript seems to be a port of [Java's](/languages/java/) <code>BigDecimal</code> class, which also supports [rounding modes](/errors/rounding/):
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var a = new BigDecimal("0.01");
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var b = new BigDecimal("0.02");
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var c = a.add(b); // 0.03
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var d = c.setScale(1, BigDecimal.prototype.ROUND_HALF_UP);
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How to Round
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------------
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num.toPrecision(1) //returns 5 as string
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num.toPrecision(2) //returns 5.1 as string
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num.toPrecision(4) //returns 5.123 as string
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TODO: talk about rounding modes; Firefox JavaScript seems to use round-half-odd
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Using a specific rounding mode:
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new BigDecimal("1.25").setScale(1, BigDecimal.prototype.ROUND_HALF_UP);
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Resources
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---------
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[BigDecimal for JavaScript](http://stz-ida.de/html/oss/js_bigdecimal.html.en)
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[Core JavaScript Reference](https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference)
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