if
Differences
This shows you the differences between two versions of the page.
| — |
if [2007/05/31 03:59] (current) |
||
|---|---|---|---|
| Line 1: | Line 1: | ||
| + | ======Synopsis:====== | ||
| + | __if__ (<condition>) <then> \\ | ||
| + | __if__ (<condition>) { <then> } [{ <else> }] \\ | ||
| + | __if__ (<condition>) { <then> } elsif (<condition>) { <then> } else { <then> } \\ | ||
| + | __if__ (<condition>) { <then> } elif (<condition>) { <then> } \\ | ||
| + | __if__ (<condition>) { <then> } else if (<condition>) { <then> } | ||
| + | |||
| + | ======Description:====== | ||
| + | __IF__ is the general purpose control statement for testing the truth/false | ||
| + | value of a given condition. If the condition is true, it performs | ||
| + | some action; if false, some alternate action. The condition does not | ||
| + | necessarily need to be a numeric comparison. It may be a function whose | ||
| + | return value is evaluated for truth or falsity, or compared against some | ||
| + | other value (which might also be a function return value). Expressions | ||
| + | are generally of the following forms: | ||
| + | |||
| + | |( exp ) |tests for existence of exp (usually a variable) | | ||
| + | |( !exp ) |tests for non-existence of exp | | ||
| + | |( exp1 == exp2 ) |tests whether exp1 equals exp2 | | ||
| + | |( exp1 != exp2 ) |tests whether exp1 does not equal exp2 | | ||
| + | |( exp1 && exp2 ) |tests for existence of exp1 and exp2 | | ||
| + | |( exp1 %%||%% exp2 ) |tests for existence of exp1 or exp2 or both | | ||
| + | |( exp1 %%^^%% exp2 ) |tests for existence of exp1 or exp2, not both | | ||
| + | |( exp1 < exp2 ) |tests whether exp1 is less than exp2 | | ||
| + | |( exp1 > exp2 ) |tests whether exp1 is more than exp2 | | ||
| + | |( exp1 <= exp2 ) |tests whether exp1 is less than or equal to exp2 | | ||
| + | |( exp1 >= exp2 ) |tests whether exp1 is more than or equal to exp2 | | ||
| + | |||
| + | The "else" portion of an __IF__ statement is not required. Additionally, | ||
| + | if the "then" portion is only a single statement, the curly braces are | ||
| + | not required either. The expression (exp) is evaluated as though it | ||
| + | were within a ${} construct, such that | ||
| + | |||
| + | if ( blah ) ... | ||
| + | |||
| + | would expand "blah" to $blah, then test the value of $blah. Variables | ||
| + | can also be placed inside the expression parser, such that | ||
| + | |||
| + | if ( [$blah] ) ... | ||
| + | |||
| + | is equivalent to the previous statement (though it isn't as efficient). | ||
| + | Both forms may be combined in the same expression. Numbers are treated | ||
| + | as constants, so in order to expand numeric expandos, such as $0, you | ||
| + | must use the expression parser, as above. Strings must also be passed | ||
| + | through the expression parser (otherwise they are interpreted as | ||
| + | variables), and are compared case-insensitively. | ||
| + | |||
| + | As in C, assignment operators may be used inside __IF__ statements. This is | ||
| + | generally not recommended, if only because it can make the code rather | ||
| + | confusing, but there are times when it can prove to be useful. The | ||
| + | following: | ||
| + | |||
| + | if ( foo = 3 > bar ) ... | ||
| + | |||
| + | would first set the value of $foo to 3, and then compare it with $bar. | ||
| + | Note that the @ operator is not needed (and in fact is not even allowed). | ||
| + | Gratuitous use of parenthesis is recommended with this notation. | ||
| + | |||
| + | Finally, as with other ircII-EPIC control statements, the curly braces | ||
| + | may be placed anywhere. | ||
| + | |||
| + | ======Examples:====== | ||
| + | The following two statements are functionally equivalent: | ||
| + | if ( foo == bar ) echo foo and bar are the same | ||
| + | if ( foo == bar ) { | ||
| + | echo foo and bar are the same | ||
| + | } | ||
| + | |||
| + | These are also equivalent: | ||
| + | if ( !foo ) ... | ||
| + | unless ( foo ) ... | ||
| + | |||
| + | Braces are required for a multi-line then portion: | ||
| + | if ( foo == bar ) { | ||
| + | echo foo and bar are the same | ||
| + | echo that's so cool! | ||
| + | } | ||
| + | |||
| + | Like other control statements, IFs may be embedded: | ||
| + | if ( foo ) { | ||
| + | if ( bar ) { | ||
| + | echo foo and bar are both non-empty! | ||
| + | echo that's so cool! | ||
| + | } | ||
| + | } | ||
| + | |||
| + | Function return values can be evaluated too: | ||
| + | if ( rmatch(foobar *blah* *bar) ) { | ||
| + | echo it matched | ||
| + | } | ||
| + | |||
| + | ======Aliases:====== | ||
| + | [[UNLESS]] is the exact opposite of __IF__. It is essentially the same applying | ||
| + | the negation operator (!) to the entire __IF__ condition. | ||
| + | |||
| + | ======Other Notes:====== | ||
| + | The "then" and "else" portions aren't required to contain anything. Use | ||
| + | of the negation operator and [[UNLESS]] obsolete this practice, however. | ||
| + | |||
if.txt ยท Last modified: 2007/05/31 03:59 (external edit)