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28.5 Delayed Evaluation


Scheme Procedure: promise? obj
C Function: scm_promise_p (obj)
Return true if obj is a promise, i.e. a delayed computation (see section `Delayed evaluation' in The Revised^5 Report on Scheme).

Scheme Procedure: force x
C Function: scm_force (x)
If the promise x has not been computed yet, compute and return x, otherwise just return the previously computed value.

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