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Manual Reference Pages  -  DECLARE::CONSTRAINTS::SIMPLE::LIBRARY::OPERATORS (3)

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NAME

Declare::Constraints::Simple::Library::Operators - Operators

CONTENTS

SYNOPSIS



  # all hast to be valid
  my $and_constraint = And( IsInt,
                            Matches(qr/0$/) );

  # at least one has to be valid
  my $or_constraint = Or( IsInt, HasLength );

  # only one can be valid
  my $xor_constraint = XOr( IsClass, IsObject );

  # reverse validity
  my $not_an_integer = Not( IsInt );

  # case valid, validate bar key depending on foo keys value
  my $struct_prof =
    And( IsHashRef,
         CaseValid( OnHashKeys(foo => IsEq("FooArray")),
                      OnHashKeys(bar => IsArrayRef),
                    OnHashKeys(foo => IsEq("FooHash")),
                      OnHashKeys(bar => IsHashRef) ));



DESCRIPTION

This module contains the frameworks operators. These constraint like elements act on the validity of passed constraints.

OPERATORS

    And(@constraints)

Is true if all passed @constraints are true on the value. Returns the result of the first failing constraint.

    Or(@constraints)

Is true if at least one of the passed @contraints is true. Returns the last failing constraint’s result if false.

    XOr(@constraints)

Valid only if a single one of the passed @constraints is valid. Returns the last failing constraint’s result if false.

    Not($constraint)

This is valid if the passed $constraint is false. The main purpose of this operator is to allow the easy reversion of a constraint’s trueness.

CaseValid($test, CW$conseq, CW$test2, CW$conseq2, ...)

This runs every given $test argument on the value, until it finds one that returns true. If none is found, false is returned. On a true result, howver, the corresponding $conseq constraint is applied to the value and it’s result returned. This allows validation depending on other properties of the value:



  my $flexible = CaseValid( IsArrayRef,
                              And( HasArraySize(1,5),
                                   OnArrayElements(0 => IsInt) ),
                            IsHashRef,
                              And( HasHashElements(qw( head tail )),
                                   OnHashKeys(head => IsInt) ));



Of course, you could model most of it probably with the other operators, but this is a bit more readable. For default cases use ReturnTrue from Declare::Constraints::Simple::Library::General as test.

SEE ALSO

Declare::Constraints::Simple, Declare::Constraints::Simple::Library

AUTHOR

Robert ’phaylon’ Sedlacek <phaylon@dunkelheit.at>

LICENSE AND COPYRIGHT

This module is free software, you can redistribute it and/or modify it under the same terms as perl itself.
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perl v5.20.3 DECLARE::CONSTRAINTS::SIMPLE::LIBRARY::OPERATORS (3) 2006-09-14

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