delay <expression> | R5RS |
The delay construct is used together with the procedure force
to implement lazy evaluation or call by need. (delay
<expression>) returns an object called a promise which at some
point in the future may be asked (by the force procedure) to
evaluate <expression> , and deliver the resulting value.
The effect of <expression> returning multiple values is unpredictable.
See the description of |
promise? obj | STKLOS Procedure |
Returns #t if obj is a promise, otherwise returns #f .
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