Lo que todo programador debería saber sobre aritmética de punto flotante
add Perl cheat sheet
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---
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title: Floating-point cheat sheet for Perl
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description: Tips for using floating-point and decimal numbers in Perl
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---
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Floating-Point Types
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--------
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Perl supports platform-native floating-point as scalar values; in practice this usually means [IEEE 754](/formats/fp/) double precision.
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Exact Types
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-------------
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Perl can also store decimal numbers as strings, but the builtin arithmetic operators will convert them to integer or floating-point values to perform the operation.
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The Math::BigFloat extension provides an arbitrary-precision [decimal type](/formats/exact/):
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use Math::BigFloat ':constant'
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my $f = 0.1 + 0.2; # returns exactly 0.3
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The Number::Fraction extension provides a fraction type that overloads the arithmetic operators with [symbolic](/formats/exact/) fraction arithmetic:
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use Number::Fraction ':constants';
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my $f = '1/2' - '1/3'; # returns 1/6
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The Math::BigRat extension provides similar functionality. Its advantage is compatibility with the Math::BigInt and Math::BigFloat extensions, but it does not seem to support fraction literals.
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How to Round
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------------
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To get a string:
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$result = sprintf("%.2f", 1.2345); # returns 1.23
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To format output:
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printf("%.2f", 1.2); # prints 1.20
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Note that this implicitly uses [round-to-even](/errors/rounding/). The variable <code>$#</code> contains the default format for printing numbers, but its use is considered deprecated.
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The Math::Round extension provides various functions for rounding floating-point values:
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use Math::Round qw(:all);
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$result = nearest(.1, 4.567) # prints 4.6
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$result = nearest(.01, 4.567) # prints 4.57
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The Math::BigFloat extension also supports various [rounding modes](/errors/rounding/):
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use Math::BigFloat;
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my $n = Math::BigFloat->new(123.455);
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my $f1 = $n->round('','-2','common'); # returns 123.46
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my $f2 = $n->round('','-2','zero'); # returns 123.45
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Resources
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---------
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* [Semantics of numbers and numeric operations in Perl](http://perldoc.perl.org/perlnumber.html)
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* [sprintf function](http://perldoc.perl.org/functions/sprintf.html)
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* [Math::Round extension](http://search.cpan.org/dist/Math-Round/Round.pm)
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* [Number::Fraction extension](http://search.cpan.org/~davecross/Number-Fraction-1.13/lib/Number/Fraction.pm)
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* [Math::BigRat extension](http://search.cpan.org/~flora/Math-BigRat-0.26/lib/Math/BigRat.pm)
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* [Math::BigFloat](http://search.cpan.org/~flora/Math-BigInt-1.95/lib/Math/BigFloat.pm)
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