1Syntax::Operator::Eqr(3U)ser Contributed Perl DocumentatiSoynntax::Operator::Eqr(3)
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6 "Syntax::Operator::Eqr" - string equality and regexp match operator
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9 On Perl v5.38 or later:
10 use v5.38;
12 use Syntax::Operator::Eqr;
13 if($str eqr $pat) {
15 say "x and y are both undef, or both defined and equal strings, " .
16 "or y is a regexp that matches x";
17 }
18 Or via Syntax::Keyword::Match on Perl v5.14 or later:
20 use v5.14;
22 use Syntax::Keyword::Match;
23 use Syntax::Operator::Eqr;
24 match($str : eqr) {
26 case(undef) { say "The variable is not defined" }
27 case("") { say "The variable is defined but is empty" }
28 case(qr/^.$/) { say "The variable contains exactly one character" }
29 default { say "The string contains more than one" }
30 }
31
33 This module provides an infix operators that implements a matching
34 operation whose behaviour depends on whether the right-hand side
35 operand is undef, a quoted regexp object, or some other value. If
36 undef, it is true only if the lefthand operand is also undef. If a
37 quoted regexp object, it behaves like Perl's "=~" pattern-matching
38 operator. If neither, it behaves like the "eq" operator.
39 This operator does not warn when either or both operands are "undef".
41 Support for custom infix operators was added in the Perl 5.37.x
43 development cycle and is available from development release v5.37.7
44 onwards, and therefore in Perl v5.38 onwards. The documentation of
45 XS::Parse::Infix describes the situation in more detail.
46 While Perl versions before this do not support custom infix operators,
48 they can still be used via "XS::Parse::Infix" and hence
49 XS::Parse::Keyword. Custom keywords which attempt to parse operator
50 syntax may be able to use these. One such module is
51 Syntax::Keyword::Match; see the SYNOPSIS example given above.
52 Comparison With Smartmatch
54 At first glance it would appear a little similar to core perl's ill-
55 fated smartmatch operator ("~~"), but this version is much simpler. It
56 does not try to determine if stringy or numerical match is preferred,
57 nor does it attempt to make sense of any "ARRAY", "HASH", "CODE" or
58 other complicated container values on either side. Its behaviour is in
59 effect entirely determined by the value on its righthand side - the
60 three cases of "undef", some "qr/.../" object, or anything else.
61 This in particular makes it behave sensibly with the "match/case"
63 syntax provided by Syntax::Keyword::Match.
64
66 eqr
67 my $matches = $lhs eqr $rhs;
68 Yields true if both operands are "undef", or if the right-hand side is
70 a quoted regexp value that matches the left-hand side, or if both are
71 defined and contain equal string values. Yields false if given exactly
72 one "undef", two unequal strings, or a string that does not match the
73 pattern.
74
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_eqr
89 my $matches = is_eqr( $lhs, $rhs );
90 A function version of the "eqr" stringy operator.
92
94 • Syntax::Operator::Equ - equality operators that distinguish "undef"
95
97 Paul Evans <leonerd@leonerd.org.uk>
98perl v5.36.1 2023-07-10 Syntax::Operator::Eqr(3)