1Syntax::Operator::Equ(3U)ser Contributed Perl DocumentatiSoynntax::Operator::Equ(3)
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6 "Syntax::Operator::Equ" - equality operators that distinguish "undef"
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9 On Perl v5.38 or later:
10 use v5.38;
12 use Syntax::Operator::Equ;
13 if($x equ $y) {
15 say "x and y are both undef, or both defined and equal strings";
16 }
17 if($i === $j) {
19 say "i and j are both undef, or both defined and equal numbers";
20 }
21 Or via Syntax::Keyword::Match on Perl v5.14 or later:
23 use v5.14;
25 use Syntax::Keyword::Match;
26 use Syntax::Operator::Equ;
27 match($str : equ) {
29 case(undef) { say "The variable is not defined" }
30 case("") { say "The variable is defined but is empty" }
31 default { say "The string is non-empty" }
32 }
33
35 This module provides infix operators that implement equality tests of
36 strings or numbers similar to perl's "eq" and "==" operators, except
37 that they consider "undef" to be a distinct value, separate from the
38 empty string or the number zero.
39 These operators do not warn when either or both operands are "undef".
41 They yield true if both operands are "undef", false if exactly one
42 operand is, or otherwise behave the same as the regular string or
43 number equality tests if both operands are defined.
44 Support for custom infix operators was added in the Perl 5.37.x
46 development cycle and is available from development release v5.37.7
47 onwards, and therefore in Perl v5.38 onwards. The documentation of
48 XS::Parse::Infix describes the situation in more detail.
49 While Perl versions before this do not support custom infix operators,
51 they can still be used via "XS::Parse::Infix" and hence
52 XS::Parse::Keyword. Custom keywords which attempt to parse operator
53 syntax may be able to use these. One such module is
54 Syntax::Keyword::Match; see the SYNOPSIS example given above.
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57 equ
58 my $equal = $lhs equ $rhs;
59 Yields true if both operands are "undef", or if both are defined and
61 contain equal string values. Yields false if given exactly one "undef",
62 or two unequal strings.
63 ===
65 my $equal = $lhs === $rhs;
66 Yields true if both operands are "undef", or if both are defined and
68 contain equal numerical values. Yields false if given exactly one
69 "undef", or two unequal numbers.
70 Note that while this operator will not cause warnings about
72 uninitialized values, it can still warn if given defined stringy values
73 that are not valid as numbers.
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76 As a convenience, the following functions may be imported which
77 implement the same behaviour as the infix operators, though are
78 accessed via regular function call syntax.
79 These wrapper functions are implemented using XS::Parse::Infix, and
81 thus have an optimising call-checker attached to them. In most cases,
82 code which calls them should not in fact have the full runtime overhead
83 of a function call because the underlying test operator will get
84 inlined into the calling code at compiletime. In effect, code calling
85 these functions should run with the same performance as code using the
86 infix operators directly.
87 is_strequ
89 my $equal = is_strequ( $lhs, $rhs );
90 A function version of the "equ" stringy operator.
92 is_numequ
94 my $equal = is_numequ( $lhs, $rgh );
95 A function version of the "===" numerical operator.
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99 • Syntax::Operator::Eqr - string equality and regexp match operator
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102 Paul Evans <leonerd@leonerd.org.uk>
103perl v5.36.1 2023-07-10 Syntax::Operator::Equ(3)