perlop: Add detail about xor #23286
perlop: Add detail about xor #23286
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pod/perlop.pod
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| X<operator, logical, xor> X<operator, logical, exclusive or> X<xor> | ||
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| Binary C<"xor"> returns the logical disjunction of the two surrounding | ||
| expressions. That means it returns 1 if either, but not both, are true. |
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Does it return 1 or true (the boolean)?
And, note that 'or' is "inclusive"; 'xor' is "exclusive" And, explicitly give the results of bitwise '|' vs '^' And, fix the incorrect use of 'binary' when 'logical' was meant. Fixes Perl#18565
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In re-reading the changes, I realized the old text wrongly used "binary" instead of "logical". Also that I had wrongly said |
| @@ -3836,6 +3849,11 @@ Here is a short, but incomplete summary: | |||
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| Choose wisely. | |||
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| =head2 Logical or and Exclusive Or | |||
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I believe these were put in the same section because the current organization of perlop is to document operators in the order of precedence, with operators of the same precedence (like or and xor) sharing a section.
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Is it then the case that there is a distinct precedence order in && || ^^ // .. as these all have their own section in this order? My guess is that || and ^^ have the same precedence.
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According to the precedence table at the top, && has a distinct precedence and || // ^^ share a precedence. Perhaps this was an oversight when adding the latter two operators.
| Binary C<"or"> returns the logical disjunction of the two surrounding | ||
| expressions. It's equivalent to C<||> except for the very low precedence. | ||
| This makes it useful for control flow: | ||
| Logical C<"or"> returns the logical inclusive disjunction of the two |
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I do not think "binary" here refers to the operation, but to the syntax of the operator: it takes two arguments. Note that the versions of these operators marked as "bitwise" as well as the C-style logical forms are also introduced with this term. In fact it is distinguishing for example binary - with unary -.
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You're right about the intent, based on looking at other portions of the document. But it confused me, and thus could easily confuse others; so some clarification is necessary.
It had not existed, until the 5.40 release. https://perldoc.perl.org/perl5400delta#New-%5E%5E-logical-xor-operator |
| expression pattern can't both match and not match, for otherwise it | ||
| would be a bug in our pattern matching code. | ||
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| ($a =~ qr/$pat/ xor $a !~ qr/$pat/) or die; |
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Avoid promoting use of $a in docs
| ($a =~ qr/$pat/ xor $a !~ qr/$pat/) or die; | |
| ($x =~ qr/$pat/ xor $x !~ qr/$pat/) or die; |
Fixes #18565