The Math::BigFloat extension also supports various rounding modes: use Math::BigFloat The Math::Round extension provides various functions for rounding floating-point values: use Math::Round qw(:all) The variable $# contains the default format for printing numbers, but its use is considered deprecated. Note that this implicitly uses round-to-even. To format output: printf("%.2f", 1.2) # prints 1.20 Scalar variable /usr/bin/perl Scalars hold just single data type: string, number or perl reference Scalars definition in Perl scalarnumber -5. Math::BigInt and Math::BigFloat extensions, but it does not seem to support fraction literals. The other approach to convert a string to a number in Perl is to just append two strings, to get an integer value. The Math::BigRat extension provides similar functionality. The Number::Fraction extension provides a fraction type that overloads the arithmetic operators with symbolic fraction arithmetic: use Number::Fraction ':constants' The Math::BigFloat extension provides an arbitrary-precision decimal type: use Math::BigFloat ':constant' 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. Perl supports platform-native floating-point as scalar values in practice this usually means IEEE 754 double precision. Format number with up to 8 leading zeroes my result sprintf(08d, number) Round number to 3 digits after decimal point my rounded sprintf(.3f. Sub ( Int:D $i is copy where * >= 0 -> Str:D ) ).reverse.join( '|' ).Floating-point cheat sheet for Perl Floating-Point Types I’ll collect the string values then join them: From that I get the base that I’ll use to decompose the number and I’ll break up the string into characters in an array so I can use the numeric value as the index to map it onto its string value. If I don’t specify a string I’ll default to the decimal digits. Specify a stupid string and get stupid number serializations. Maybe they aren’t in order of their codepoints, or they are repeated, or some other weird thing. ![]() I don’t care which characters are in the string. I create a factory that takes a single string where each character represents a digit the number of digits is the base. Optimizing that lookup table is most of the problem but I don’t worry about that right away. Put together all your string parts to get the full number. The solution is to decompose a number into parts and convert that partto a string with a lookup table. How about a converter for arbitrary bases with arbitrary digits? And, I can’t use any of the builtin stuff to make this work (and so far I haven’t peeked to see how Rakudo does it). There are probably some hexadecimal converters out there. ![]() ![]() The solutions I found convert everything to decimal numbers. Perl Automatic String to Number Conversion or Casting Convert an integer to a binary string with leading zeros in C Perl concatenate string Working of String. Since this is also a typical interview problem I thought I’d work on it in Perl 6 with a few extras. Much of his discussion is special to C or C++ where you (think) you directly control the hardware. If you’ve bought into the JSON mania you’re probably serializing numbers as strings quite a bit without even thinking about it. Hex to String converters can be used for a variety of purposes, such as converting data values into a human-readable format or converting code values into a. Paul Khuong wrote about this in How to Print Integers Really Fast (With Open Source AppNexus Code!). Turning numbers into strings can be a big waste of time and money.
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