SRFI 65: define-immutable: A Syntax to Define Identifiers With Immutable Values

by Andrew Wilcox

status: withdrawn (2005-05-17)

keywords: Binding, Lazy Evaluation


The define-immutable form defines an identifier whose value never changes.

The expression part of the definition is evaluated lazily: it is not evaluated unless and until the identifier is evaluated. This permits an immutable definition to use other definitions in more ways than is possible when using define in internal definitions.

A series of immutable definitions have simple semantics, making them easy to program and understand.

    (let ()
      (define-immutable x (+ z 5))
      (define-immutable y (/ 100 4))
      (define-immutable z (add-10 y))
      (define-immutable add-10 (add-n 10))
      (define-immutable (add-n n)
        (lambda (x)
          (+ n x)))