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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 is it contains. If we later write the condition >=(expr1,34) it's equivalent to the condition >=(+(var1,var2,3),34).
The reward definition file:
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