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.IX Title "Declare::Constraints::Simple::Library::Operators 3pm"
.TH Declare::Constraints::Simple::Library::Operators 3pm "2018-03-31" "perl v5.26.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.SH "NAME"
Declare::Constraints::Simple::Library::Operators \- Operators
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 3
\&  # 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 \*(Aqbar\*(Aq key depending on \*(Aqfoo\*(Aq keys value
\&  my $struct_prof = 
\&    And( IsHashRef,
\&         CaseValid( OnHashKeys(foo => IsEq("FooArray")),
\&                      OnHashKeys(bar => IsArrayRef),
\&                    OnHashKeys(foo => IsEq("FooHash")),
\&                      OnHashKeys(bar => IsHashRef) ));
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module contains the frameworks operators. These constraint like
elements act on the validity of passed constraints.
.SH "OPERATORS"
.IX Header "OPERATORS"
.SS "And(@constraints)"
.IX Subsection "And(@constraints)"
Is true if all passed \f(CW@constraints\fR are true on the value. Returns
the result of the first failing constraint.
.SS "Or(@constraints)"
.IX Subsection "Or(@constraints)"
Is true if at least one of the passed \f(CW@contraints\fR is true. Returns the
last failing constraint's result if false.
.SS "XOr(@constraints)"
.IX Subsection "XOr(@constraints)"
Valid only if a single one of the passed \f(CW@constraints\fR is valid. Returns
the last failing constraint's result if false.
.SS "Not($constraint)"
.IX Subsection "Not($constraint)"
This is valid if the passed \f(CW$constraint\fR is false. The main purpose
of this operator is to allow the easy reversion of a constraint's 
trueness.
.ie n .SS "CaseValid($test, $conseq, $test2, $conseq2, ...)"
.el .SS "CaseValid($test, \f(CW$conseq\fP, \f(CW$test2\fP, \f(CW$conseq2\fP, ...)"
.IX Subsection "CaseValid($test, $conseq, $test2, $conseq2, ...)"
This runs every given \f(CW$test\fR argument on the value, until it finds
one that returns true. If none is found, false is returned. On a true
result, however, the corresponding \f(CW$conseq\fR constraint is applied to
the value and it's result returned. This allows validation depending
on other properties of the value:
.PP
.Vb 6
\&  my $flexible = CaseValid( IsArrayRef,
\&                              And( HasArraySize(1,5), 
\&                                   OnArrayElements(0 => IsInt) ),
\&                            IsHashRef,
\&                              And( HasHashElements(qw( head tail )),
\&                                   OnHashKeys(head => IsInt) ));
.Ve
.PP
Of course, you could model most of it probably with the other
operators, but this is a bit more readable. For default cases use
\&\f(CW\*(C`ReturnTrue\*(C'\fR from Declare::Constraints::Simple::Library::General
as test.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Declare::Constraints::Simple, Declare::Constraints::Simple::Library
.SH "AUTHOR"
.IX Header "AUTHOR"
Robert 'phaylon' Sedlacek \f(CW\*(C`<phaylon@dunkelheit.at>\*(C'\fR
.SH "LICENSE AND COPYRIGHT"
.IX Header "LICENSE AND COPYRIGHT"
This module is free software, you can redistribute it and/or modify it 
under the same terms as perl itself.