Function if - Revision history

Diemo: Category:Functions

2010-08-06T09:48:17Z

Category:Functions

Diemo: see also

2010-08-06T09:41:32Z

Diemo at 09:41, 6 August 2010

2010-08-06T09:41:18Z

Diemo: from mail 5.5.2009

2010-08-06T09:39:44Z

from mail 5.5.2009

New page

===Syntax===

<code>if <num: condition> <any: true value> [<any: false value>]</code>

===Synopsis:===

Choose between two values (both conditional values are evaluated). If the <false value> argument is missing, nothing is output.

===Description===

The ''if'' function (not method) should be pretty clear if you keep in mind the
two drawbacks:

1. it is a function, i.e. all three arguments are evaluated before the ''if'' gets to
decide which one to output, i.e. something like

(if ($1 != 1) ($myfmat mul 2) ($myfmat zero))

always multiplies and then zeros the myfmat!

2. The result of ''if'' can only be one atom, not a list. If you want to output
one list or another, use tuples, with a subsequent ftm.list, the ''list'' function, or the
''output tuples as list'' (''untuple'') inspector option of ftm.mess. This can be used with a 'route'
to send different lists out to one or another connection, like this:

(if ($mydict exists $1) {1 $mydict[$1]} {2 $1 42})
|
ftm.list
|
route 1 2

or

(list (if ($mydict exists $1) {1 $mydict[$1]} {2 $1 42}))
|
route 1 2

or with ''untuple''

(if ($mydict exists $1) {1 $mydict[$1]} {2 $1 42})
|
route 1 2

'''See also:''' [[How can I work with lists passed to an ftm.mess object?]]

[[Category:Expressions]] [[Category:ftm.mess]] [[Category:FTM Documentation]]

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		+	[[How can I work with lists passed to an ftm.mess object?]]

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 ===See also===
- [[How can I work with lists passed to an ftm.mess object?]]
+[[How can I work with lists passed to an ftm.mess object?]]
 [[Category:Expressions]] [[Category:ftm.mess]] [[Category:FTM Documentation]]