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1. isCurrentTopic(var): returns true if the provided string or variable containing a string matches one of the topics of the sub-dialogue currently active.
2. known(expr): this returns true of the provided expression evaluates to anything but the NULL value.
3. isLastNonNullTopic(var): similar to isCurrentTopic but executes the match on the last non null topic. That is, if currently there are no active networks, this will match the value of var with the topic of the last active network.
4. isQuestion(var): returns true if the provided var evaluates to a string that contains the string "question". This maps to the method edu.usc.ict.nl.io.NLU.isQuestion overwrite with your own specific NLU class if you want to customize or write a new custom function.
5. match(var1,var2): maps to the String.matches(regexp) Java method. var1 must be a string or evaluate to one. var2 must be a string or evaluate to one. The content of var2 must be a valid Java regular expression.
6. random(var): generates a random number from 0 to the value in var-1. var doesn't have to be a variable but can also be a numeric constant.

Quotation

Delayed evaluation is available using the special operator quote. For example, if we execute this assignment assign(expr1,quote(+(var1,var2,3))) we save in the variable expr1 the expression that computes the sum of var1, var2 and the constant 3. every time we use the variable expr1 it's like if we use the entire expression it contains. If we later write the condition >=(expr1,34) it's equivalent to the condition >=(+(var1,var2,3),34).

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