Provided by: libnumber-tolerant-perl_1.708-2_all bug


       Number::Tolerant - tolerance ranges for inexact numbers


       version 1.708


        use Number::Tolerant;

        my $range  = tolerance(10 => to => 12);
        my $random = 10 + rand(2);

        die "I shouldn't die" unless $random == $range;

        print "This line will always print.\n";


       Number::Tolerant creates a number-like object whose value refers to a range of possible
       values, each equally acceptable.  It overloads comparison operations to reflect this.

       I use this module to simplify the comparison of measurement results to specified

        reject $product unless $measurement == $specification;




       There is a "new" method on the Number::Tolerant class, but it also exports a simple
       function, "tolerance", which will return an object of the Number::Tolerant class.  Both
       use the same syntax:

        my $range = Number::Tolerant->new( $x => $method => $y);

        my $range = tolerance( $x => $method => $y);

       The meaning of $x and $y are dependent on the value of $method, which describes the nature
       of the tolerance.  Tolerances can be defined in five ways, at present:

         method              range
         plus_or_minus     | x +/- y
         plus_or_minus_pct | x +/- (y% of x)
         or_more           | x to Inf
         or_less           | x to -Inf
         more_than         | x to Inf, not x
         less_than         | x to -Inf, not x
         to                | x to y
         infinite          | -Inf to Inf
         offset            | (x + y1) to (x + y2)

       For "or_less" and "or_more", $y is ignored if passed.  For "infinite", neither $x nor $y
       is used; "infinite" should be the sole argument.  The first two arguments can be reversed
       for "more_than" and "less_than", to be more English-like.

       Offset tolerances are slightly unusual.  Here is an example:

         my $offset_tolerance = tolerance(10 => offset => (-3, 5));
         # stringifies to: 10 (-3 +5)

       An offset is very much like a "plus_or_minus" tolerance, but its center value is not
       necessarily the midpoint between its extremes.  This is significant for comparisons and
       numifications of the tolerance.  Given the following two tolerances:

         my $pm_dice = tolerance(10.5 => plus_or_minus => 7.5);
         my $os_dice = tolerance(11 => offset => (-8, 7));

       The first will sort as numerically less than the second.

       If the given arguments can't be formed into a tolerance, an exception will be raised.


       A new tolerance can be instantiated from the stringification of an old tolerance.  For

        my $range = Number::Tolerant->from_string("10 to 12");

        die "Everything's OK!" if 11 == $range; # program dies of joy

       This will not yet parse stringified unions, but that will be implemented in the future.
       (I just don't need it yet.)

       If a string can't be parsed, an exception is raised.

         my $string = $tolerance->stringify_as($type);

       This method does nothing!  Someday, it will stringify the given tolerance as a different
       type, if possible.  "10 +/- 1" will "stringify_as('plus_or_minus_pct')" to "10 +/- 10%"
       for example.

         my $n = $tolerance->numify;

       This returns the numeric form of a tolerance.  If a tolerance has both a minimum and a
       maximum, and they are the same, then that is the numification.  Otherwise, numify returns

       Tolerances overload a few operations, mostly comparisons.

           Tolerances are always true.

           Most tolerances numify to undef; see "numify".

           A tolerance stringifies to a short description of itself, generally something like "m
           < x < n"

            infinite  - "any number"
            to        - "m <= x <= n"
            or_more   - "m <= x"
            or_less   - "x <= n"
            more_than - "m < x"
            less_than - "x < n"
            offset    - "x (-y1 +y2)"
            constant  - "x"
            plus_or_minus     - "x +/- y"
            plus_or_minus_pct - "x +/- y%"

           A number is equal to a tolerance if it is neither less than nor greater than it.  (See

       smart match
           Same as equality.

           A number is greater than a tolerance if it is greater than its maximum value.

           A number is less than a tolerance if it is less than its minimum value.

           No number is greater than an "or_more" tolerance or less than an "or_less" tolerance.

           "...or equal to" comparisons include the min/max values in the permissible range, as
           common sense suggests.

       tolerance intersection
           A tolerance "&" a tolerance or number is the intersection of the two ranges.
           Intersections allow you to quickly narrow down a set of tolerances to the most
           stringent intersection of values.

            tolerance(5 => to => 6) & tolerance(5.5 => to => 6.5);
            # this yields: tolerance(5.5 => to => 6)

           If the given values have no intersection, "()" is returned.

           An intersection with a normal number will yield that number, if it is within the

       tolerance union
           A tolerance "|" a tolerance or number is the union of the two.  Unions allow multiple
           tolerances, whether they intersect or not, to be treated as one.  See
           Number::Tolerant::Union for more information.


       This feature is slighly experimental, but it's here.

       New tolerance types may be written as subclasses of Number::Tolerant::Type, providing the
       interface described in its documentation.  They can then be enabled or disabled with the
       following methods:

   " enable_plugin "

       This method enables the named class, so that attempts to create new tolerances will check
       against this class.  Classes are checked against "validate_plugin" before being enabled.
       An exception is thrown if the class does not appear to provide the Number::Tolerant::Type

   " disable_plugin "

       This method will disable the named class, so that future attempts to create new tolerances
       will not check against this class.

   " validate_plugin "

       This method checks (naively) that the given class provides the interface defined in
       Number::Tolerant::Type.  If it does not, an exception is thrown.


       ·   Extend "from_string" to cover unions.

       ·   Extend "from_string" to include Number::Range-type specifications.

       ·   Allow translation into forms not originally used:

            my $range    = tolerance(9 => to => 17);
            my $range_pm = $range->convert_to('plus_minus');

       ·   Create a factory so that you can simultaneously work with two sets of plugins.

           This one is very near completion.  There will now be two classes that should be used:
           Number::Tolerant::Factory, which produces tolerances, and Number::Tolerant::Tolerance,
           which is a tolerance.  Both will inherit from N::T, for supporting old code, and N::T
           will dispatch construction methods to a default factory.


       The module Number::Range provides another way to deal with ranges of numbers.  The major
       differences are: N::R is set-like, not range-like; N::R does not overload any operators.
       Number::Tolerant will not (like N::R) attempt to parse a textual range specification like
       "1..2,5,7..10" unless specifically instructed to.  (The valid formats for strings passed
       to "from_string" does not match Number::Range exactly.  See TODO.)

       The "Number::Range" code:

        $range = Number::Range->new("10..15","20..25");

       Is equivalent to the "Number::Tolerant" code:

        $range = Number::Tolerant::Union->new(10..15,20..25);

       ...while the following code expresses an actual range:

        $range = tolerance(10 => to => 15) | tolerance(20 => to => 25);


       Thanks to Yuval Kogman and #perl-qa for helping find the bizarre bug that drove the
       minimum required perl up to 5.8

       Thanks to Tom Freedman, who reminded me that this code was fun to work on, and also
       provided the initial implementation for the offset type.


       Ricardo Signes <>


       ·   Alexandre Mestiashvili <>

       ·   Karen Etheridge <>

       ·   Michael Carman <>

       ·   Ricardo SIGNES <>

       ·   Smylers <>


       This software is copyright (c) 2004 by Ricardo Signes.

       This is free software; you can redistribute it and/or modify it under the same terms as
       the Perl 5 programming language system itself.