► |  | How to Design Programs Languages

1 | Beginning Student
2 | Beginning Student with List Abbreviations
3 | Intermediate Student
4 | Intermediate Student with Lambda
5 | Advanced Student
| Index

▼ | 5 | Advanced Student

5.1 | define
5.2 | define-struct
5.3 | lambda
5.4 | Function Calls
5.5 | begin
5.6 | begin0
5.7 | set!
5.8 | delay
5.9 | shared
5.10 | let
5.11 | recur
5.12 | case
5.13 | when and unless
5.14 | Primitive Operations
5.15 | Unchanged Forms

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delay

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#### 5.8`` delay

( delay expr)

Produces a “promise” to evaluate expr. The expr is not evaluated until the promise is forced through the force operator; when the promise is forced, the result is recorded, so that any further force of the promise always produces the remembered value.
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