Scalar::Number(3pm)					User Contributed Perl Documentation				       Scalar::Number(3pm)

NAME

       Scalar::Number - numeric aspects of scalars

SYNOPSIS

	       use Scalar::Number qw(scalar_num_part);

	       $num = scalar_num_part($scalar);

	       use Scalar::Number qw(sclnum_is_natint sclnum_is_float);

	       if(sclnum_is_natint($value)) { ...
	       if(sclnum_is_float($value)) { ...

	       use Scalar::Number qw(sclnum_val_cmp sclnum_id_cmp);

	       @sorted_nums = sort { sclnum_val_cmp($a, $b) } @floats;
	       @sorted_nums = sort { sclnum_id_cmp($a, $b) } @floats;

DESCRIPTION

       This module is about the numeric part of plain (string) Perl scalars.  A scalar has a numeric value, which may be expressed in either the
       native integer type or the native floating point type.  Many values are expressible both ways, in which case the exact representation is
       insignificant.  To fully understand Perl arithmetic it is necessary to know about both of these representations, and the differing
       behaviours of numbers according to which way they are expressible.

       This module provides functions to extract the numeric part of a scalar, classify a number by expressibility, and compare numbers across
       representations.

       This module is implemented in XS, with a pure Perl backup version for systems that can't handle XS.

FUNCTIONS

       Each "sclnum_" function takes one or more scalar numeric arguments to operate on.  These arguments must be numeric; giving non-numeric
       arguments will cause mayhem.  See "is_number" in Params::Classify for a way to check for numericness.  Only the numeric value of the scalar
       is used; the string value is completely ignored, so dualvars are not a problem.

   Decomposition
       scalar_num_part(SCALAR)
	   Extracts the numeric value of SCALAR, and returns it as a pure numeric scalar.  The argument is permitted to be any scalar.

	   Every scalar has both a string value and a numeric value.  In pure string scalars, those resulting from string literals or string
	   operations, the numeric value is determined from the string value.  In pure numeric scalars, those resulting from numeric literals or
	   numeric operations, the string value is determined from the numeric value.  In the general case, however, a plain scalar's string and
	   numeric values may be set independently, which is known as a dualvar.  Non-plain scalars, principally references, determine their
	   string and numeric values in other ways, and in particular a reference to a blessed object can stringify and numerify however the class
	   wishes.

	   This function does not warn if given an ostensibly non-numeric argument, because the whole point of it is to extract the numeric value
	   of scalars that are not pure numeric.

   Classification
       sclnum_is_natint(VALUE)
	   Returns a truth value indicating whether the provided VALUE can be represented in the native integer data type.  If the floating point
	   type includes signed zeroes then they do not qualify; the only zero representable in the integer type is unsigned.

       sclnum_is_float(VALUE)
	   Returns a truth value indicating whether the provided VALUE can be represented in the native floating point data type.  If the floating
	   point type includes signed zeroes then an unsigned zero (from the native integer type) does not qualify.

   Comparison
       sclnum_val_cmp(A, B)
	   Numerically compares the values A and B.  Integer and floating point values are compared correctly with each other, even if there is no
	   available format in which both values can be accurately represented.  Returns -1, 0, +1, or undef, indicating whether A is less than,
	   equal to, greater than, or not comparable with B.  The "not comparable" situation arises if either value is a floating point NaN (not-
	   a-number).  All flavours of zero compare equal.

	   This is very similar to Perl's built-in <=> operator.  The only difference is the capability to compare integer against floating point
	   (where neither can be represented exactly in the other's format).  <=> performs such comparisons in floating point, losing accuracy of
	   the integer value.

       sclnum_id_cmp(A, B)
	   This is a comparison function supplying a total ordering of scalar numeric values.  Returns -1, 0, or +1, indicating whether A is to be
	   sorted before, the same as, or after B.

	   The ordering is of the identities of numeric values, not their numerical values.  If floating point zeroes are signed, then the three
	   types (positive, negative, and unsigned) are considered to be distinct.  NaNs compare equal to each other, but different from all
	   numeric values.  The exact ordering provided is mostly numerical order: NaNs come first, followed by negative infinity, then negative
	   finite values, then negative zero, then unsigned zero, then positive zero, then positive finite values, then positive infinity.

	   In addition to sorting, this function can be useful to check for a zero of a particular sign.

BUGS

       In Perl 5.6, if configured with a wider-than-usual native integer type such that there are native integers that can't be represented
       exactly in the native floating point type, it is not always possible to distinguish between integer and floating point values in pure Perl
       code.  In order to get the full benefit of either type, one is expected (by the numeric semantics) to know in advance which of them one is
       using.  The pure Perl version of this module can't operate on such a system, but the XS version works fine.  This problem is resolved by
       Perl 5.8's new numeric semantics.

SEE ALSO

       Data::Float, Data::Integer, perlnumber(1)

AUTHOR

       Andrew Main (Zefram) <zefram@fysh.org>

COPYRIGHT

       Copyright (C) 2007, 2009, 2010 Andrew Main (Zefram) <zefram@fysh.org>

LICENSE

       This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perl v5.14.2							    2011-11-15						       Scalar::Number(3pm)