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NAME
Syntax::Operator::Equ - equality operators that distinguish undef
SYNOPSIS
On Perl v5.38 or later:
use v5.38;
use Syntax::Operator::Equ;
if($x equ $y) {
say "x and y are both undef, or both defined and equal strings";
}
if($i === $j) {
say "i and j are both undef, or both defined and equal numbers";
}
Or via Syntax::Keyword::Match on Perl v5.14 or later:
use v5.14;
use Syntax::Keyword::Match;
use Syntax::Operator::Equ;
match($str : equ) {
case(undef) { say "The variable is not defined" }
case("") { say "The variable is defined but is empty" }
default { say "The string is non-empty" }
}
DESCRIPTION
This module provides infix operators that implement equality tests of
strings or numbers similar to perl's eq and == operators, except that
they consider undef to be a distinct value, separate from the empty
string or the number zero.
These operators do not warn when either or both operands are undef.
They yield true if both operands are undef, false if exactly one
operand is, or otherwise behave the same as the regular string or
number equality tests if both operands are defined.
Support for custom infix operators was added in the Perl 5.37.x
development cycle and is available from development release v5.37.7
onwards, and therefore in Perl v5.38 onwards. The documentation of
XS::Parse::Infix describes the situation in more detail.
While Perl versions before this do not support custom infix operators,
they can still be used via XS::Parse::Infix and hence
XS::Parse::Keyword. Custom keywords which attempt to parse operator
syntax may be able to use these. One such module is
Syntax::Keyword::Match; see the SYNOPSIS example given above.
OPERATORS
equ
my $equal = $lhs equ $rhs;
Yields true if both operands are undef, or if both are defined and
contain equal string values. Yields false if given exactly one undef,
or two unequal strings.
===
my $equal = $lhs === $rhs;
Yields true if both operands are undef, or if both are defined and
contain equal numerical values. Yields false if given exactly one
undef, or two unequal numbers.
Note that while this operator will not cause warnings about
uninitialized values, it can still warn if given defined stringy values
that are not valid as numbers.
FUNCTIONS
As a convenience, the following functions may be imported which
implement the same behaviour as the infix operators, though are
accessed via regular function call syntax.
These wrapper functions are implemented using XS::Parse::Infix, and
thus have an optimising call-checker attached to them. In most cases,
code which calls them should not in fact have the full runtime overhead
of a function call because the underlying test operator will get
inlined into the calling code at compiletime. In effect, code calling
these functions should run with the same performance as code using the
infix operators directly.
is_strequ
my $equal = is_strequ( $lhs, $rhs );
A function version of the "equ" stringy operator.
is_numequ
my $equal = is_numequ( $lhs, $rgh );
A function version of the "===" numerical operator.
SEE ALSO
* Syntax::Operator::Eqr - string equality and regexp match operator
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
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