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On this page:

mark-parameter
mark-parameter-first
mark-parameter-all
mark-parameters-all
mark-parameterize

Version: 5.3.1
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### 20`` Mark Parameters

Jay McCarthy <jay@racket-lang.org>

This library is unstable; compatibility will not be maintained. See Unstable: May Change Without Warning for more information.

( require unstable/markparam )

This library provides a simplified version of parameters that are backed by continuation marks, rather than parameterizations. This means they are slightly slower, are not inherited by child threads, do not have initial values, and cannot be imperatively mutated.

> > struct

> > ( struct mark-parameter ())

The struct for mark parameters. It is guaranteed to be serializable and transparent. If used as a procedure, it calls mark-parameter-first on itself.

> > procedure

> > ( mark-parameter-first mp [tag]) → any/c

> mp : mark-parameter?

> | tag |  | : |  | continuation-prompt-tag?
> |  |  | = |  | default-continuation-prompt-tag

Returns the first value of mp up to tag.

> > procedure

> > ( mark-parameter-all mp [tag]) → list?

> mp : mark-parameter?

> | tag |  | : |  | continuation-prompt-tag?
> |  |  | = |  | default-continuation-prompt-tag

Returns the values of mp up to tag.

> > procedure

> > ( mark-parameters-all mps none-v [tag]) → ( listof vector? )

> mps : ( listof mark-parameter? )
> none-v : [ any/c #f]

> | tag |  | : |  | continuation-prompt-tag?
> |  |  | = |  | default-continuation-prompt-tag

Returns the values of the mps up to tag. The length of each vector in the result list is the same as the length of mps, and a value in a particular vector position is the value for the corresponding mark parameter in mps. Values for multiple mark parameter appear in a single vector only when the mark parameters are for the same continuation frame in the current continuation. The none-v argument is used for vector elements to indicate the lack of a value.

> > syntax

> > ( mark-parameterize ([mp expr] ...) body-expr ...)

Parameterizes ( begin body-expr ... ) by associating each mp with the evaluation of expr in the parameterization of the entire expression.
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