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| control structure | when, unless | ||||
| Related Syntax | Related Concepts | ||||
Syntax
action|rule when condition action|rule unless condition
Where:
action
rule
condition
You can usewhen and unless to make any OmniMark rule or action conditional. The rule will not fire, the action will not be executed, if the condition following when is false, or the condition following unless is true.
The following rule will fire when "hello" occurs in the data only if "count" is greater than 12:
find "hello" when count > 12
The following action will be executed unless the variable "name" contains the string "Fred":
output name unless name = "Fred"
when and unless can also be used to make any block or looping structure conditional by placing them at the end of the structure:
do xml-parse document scan my-document
output"%c"
done unless my-flag
This is not particulary readable, however. It will usually be preferable to wrap the structure you want to make conditional in a do when or do unless block:
do unless my-flag
do xml-parse document scan my-document
output "%c"
done
done
Note that do when and do unless are separate conditional structures, not do blocks with when or unless attached. do when and do unless allow for the use of else and else when within the block.
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Related Syntax do when, do unless true, false |
Related Concepts Conditional constructs |
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