1Syntax::Operator::Equ(3U)ser Contributed Perl DocumentatiSoynntax::Operator::Equ(3)
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NAME

6       "Syntax::Operator::Equ" - equality operators that distinguish "undef"
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SYNOPSIS

9       On a suitably-patched perl:
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11          use Syntax::Operator::Equ;
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13          if($x equ $y) {
14             say "x and y are both undef, or both defined and equal strings";
15          }
16
17          if($i === $j) {
18             say "i and j are both undef, or both defined and equal numbers";
19          }
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21       Or, on a standard perl via Syntax::Keyword::Match:
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23          use v5.14;
24          use Syntax::Keyword::Match;
25          use Syntax::Operator::Equ;
26
27          match($str : equ) {
28             case(undef) { say "The variable is not defined" }
29             case("")    { say "The variable is defined but is empty" }
30             default     { say "The string is non-empty" }
31          }
32

DESCRIPTION

34       This module provides infix operators that implement equality tests of
35       strings or numbers similar to perl's "eq" and "==" operators, except
36       that they consider "undef" to be a distinct value, separate from the
37       empty string or the number zero.
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39       These operators do not warn when either or both operands are "undef".
40       They yield true if both operands are "undef", false if exactly one
41       operand is, or otherwise behave the same as the regular string or
42       number equality tests if both operands are defined.
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44       Current versions of perl do not directly support custom infix
45       operators. The documentation of XS::Parse::Infix describes the
46       situation, with reference to a branch experimenting with this new
47       feature. This module is therefore almost entirely useless on standard
48       perl builds. While the regular parser does not support custom infix
49       operators, they are supported via "XS::Parse::Infix" and hence
50       XS::Parse::Keyword, and so custom keywords which attempt to parse
51       operator syntax may be able to use it. One such module is
52       Syntax::Keyword::Match; see the SYNOPSIS example given above.
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OPERATORS

55   equ
56          my $equal = $lhs equ $rhs;
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58       Yields true if both operands are "undef", or if both are defined and
59       contain equal string values. Yields false if given exactly one "undef",
60       or two unequal strings.
61
62   ===
63          my $equal = $lhs === $rhs;
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65       Yields true if both operands are "undef", or if both are defined and
66       contain equal numerical values. Yields false if given exactly one
67       "undef", or two unequal numbers.
68
69       Note that while this operator will not cause warnings about
70       uninitialized values, it can still warn if given defined stringy values
71       that are not valid as numbers.
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FUNCTIONS

74       As a convenience, the following functions may be imported which
75       implement the same behaviour as the infix operators, though are
76       accessed via regular function call syntax.
77
78       These wrapper functions are implemented using XS::Parse::Infix, and
79       thus have an optimising call-checker attached to them. In most cases,
80       code which calls them should not in fact have the full runtime overhead
81       of a function call because the underlying test operator will get
82       inlined into the calling code at compiletime. In effect, code calling
83       these functions should run with the same performance as code using the
84       infix operators directly.
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86   is_strequ
87          my $equal = is_strequ( $lhs, $rhs );
88
89       A function version of the "equ" stringy operator.
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91   is_numequ
92          my $equal = is_numequ( $lhs, $rgh );
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94       A function version of the "===" numerical operator.
95

AUTHOR

97       Paul Evans <leonerd@leonerd.org.uk>
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101perl v5.34.0                      2021-11-12          Syntax::Operator::Equ(3)
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