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Diffstat (limited to 'Help/command/if.rst')
| -rw-r--r-- | Help/command/if.rst | 37 |
1 files changed, 27 insertions, 10 deletions
diff --git a/Help/command/if.rst b/Help/command/if.rst index 5dba13ef3..4f955db0e 100644 --- a/Help/command/if.rst +++ b/Help/command/if.rst @@ -38,21 +38,29 @@ The following syntax applies to the ``condition`` argument of the ``if``, ``elseif`` and :command:`while` clauses. Compound conditions are evaluated in the following order of precedence: -Innermost parentheses are evaluated first. Next come unary tests such -as `EXISTS`_, `COMMAND`_, and `DEFINED`_. Then binary tests such as -`EQUAL`_, `LESS`_, `LESS_EQUAL`_, `GREATER`_, `GREATER_EQUAL`_, -`STREQUAL`_, `STRLESS`_, `STRLESS_EQUAL`_, `STRGREATER`_, -`STRGREATER_EQUAL`_, `VERSION_EQUAL`_, `VERSION_LESS`_, -`VERSION_LESS_EQUAL`_, `VERSION_GREATER`_, `VERSION_GREATER_EQUAL`_, -and `MATCHES`_. Then the boolean operators in the order `NOT`_, `AND`_, -and finally `OR`_. + +1. Parentheses. + +2. Unary tests such as `EXISTS`_, `COMMAND`_, and `DEFINED`_. + +3. Binary tests such as `EQUAL`_, `LESS`_, `LESS_EQUAL`_, `GREATER`_, + `GREATER_EQUAL`_, `STREQUAL`_, `STRLESS`_, `STRLESS_EQUAL`_, + `STRGREATER`_, `STRGREATER_EQUAL`_, `VERSION_EQUAL`_, `VERSION_LESS`_, + `VERSION_LESS_EQUAL`_, `VERSION_GREATER`_, `VERSION_GREATER_EQUAL`_, + and `MATCHES`_. + +4. Unary logical operator `NOT`_. + +5. Binary logical operators `AND`_ and `OR`_, from left to right, + without any short-circuit. Basic Expressions """"""""""""""""" ``if(<constant>)`` True if the constant is ``1``, ``ON``, ``YES``, ``TRUE``, ``Y``, - or a non-zero number. False if the constant is ``0``, ``OFF``, + or a non-zero number (including floating point numbers). + False if the constant is ``0``, ``OFF``, ``NO``, ``FALSE``, ``N``, ``IGNORE``, ``NOTFOUND``, the empty string, or ends in the suffix ``-NOTFOUND``. Named boolean constants are case-insensitive. If the argument is not one of these specific @@ -126,7 +134,16 @@ Existence Checks ``if(DEFINED <name>|CACHE{<name>}|ENV{<name>})`` True if a variable, cache variable or environment variable with given ``<name>`` is defined. The value of the variable - does not matter. Note that macro arguments are not variables. + does not matter. Note the following caveats: + + * Macro arguments are not variables. + * It is not possible to test directly whether a `<name>` is a non-cache + variable. The expression ``if(DEFINED someName)`` will evaluate to true + if either a cache or non-cache variable ``someName`` exists. In + comparison, the expression ``if(DEFINED CACHE{someName})`` will only + evaluate to true if a cache variable ``someName`` exists. Both expressions + need to be tested if you need to know whether a non-cache variable exists: + ``if(DEFINED someName AND NOT DEFINED CACHE{someName})``. .. versionadded:: 3.14 Added support for ``CACHE{<name>}`` variables. |