#lang scribble/manual
@(require "utils.rkt" (for-label racket unstable/markparam))

@title{Mark Parameters}

@defmodule[unstable/markparam]

@unstable[@author+email["Jay McCarthy" "jay@racket-lang.org"]]

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.

@defstruct*[mark-parameter ()]{
 The struct for mark parameters. It is guaranteed to be serializable and transparent. If used as a procedure, it calls @racket[mark-parameter-first] on itself.
 }

@defproc[(mark-parameter-first [mp mark-parameter?]
                               [tag continuation-prompt-tag? default-continuation-prompt-tag])
         any/c]{
 Returns the first value of @racket[mp] up to @racket[tag].
 }
               
@defproc[(mark-parameter-all [mp mark-parameter?]
                             [tag continuation-prompt-tag? default-continuation-prompt-tag])
         list?]{
 Returns the values of @racket[mp] up to @racket[tag].
 }   
  
@defproc[(mark-parameters-all [mps (listof mark-parameter?)]
                              [none-v [any/c #f]]
                              [tag continuation-prompt-tag? default-continuation-prompt-tag])
         (listof vector?)]{
 Returns the values of the @racket[mps] up to @racket[tag]. The length of each vector in the result list is the same as the length of @racket[mps], and a value in a particular vector position is the value for the corresponding mark parameter in @racket[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 @racket[none-v] argument is used for vector elements to indicate the lack of a value.
 }
                          
@defform[(mark-parameterize ([mp expr] ...) body-expr ...)]{
 Parameterizes @racket[(begin body-expr ...)] by associating each @racket[mp] with the evaluation of @racket[expr] in the parameterization of the entire expression.
 }