3 Mutable List Functions

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3.1 | Legacy Racket Mutable List Library

On this page:

mlist?
mlist
list->mlist
mlist->list
mlength
mlist-ref
mlist-tail
mappend
mappend!
mreverse
mreverse!
mmap
mfor-each
mmember
mmemv
mmemq
massoc
massv
massq
mlistof
3.1`` Legacy Racket Mutable List Library

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### 3`` Mutable List Functions

(require compatibility/mlist)

This compatibility/mlist library provides support for mutable lists. Support is provided primarily to help porting Lisp/Scheme code to Racket.

Use of mutable lists for modern Racket code is strongly discouraged. Instead, consider using lists.

For functions described in this section, contracts are not directly enforced. In particular, when a mutable list is expected, supplying any other kind of value (or mutating a value that starts as a mutable list) tends to produce an exception from mcar or mcdr.

> procedure (mlist? v) → boolean?
> v : any/c

Returns #t if v is a mutable list: either the empty list, or a mutable pair whose second element is a mutable list.

> procedure (mlist v ...) → mlist?
> v : any/c

Returns a newly allocated mutable list containing the vs as its elements.

> procedure (list->mlist lst) → mlist?
> lst : list?

Returns a newly allocated mutable list with the same elements as lst.

> procedure (mlist->list mlst) → list?
> mlst : mlist?

Returns a newly allocated list with the same elements as mlst.

> procedure (mlength mlst) → exact-nonnegative-integer?
> mlst : mlist?

Returns the number of elements in mlst.

> procedure (mlist-ref mlst pos) → any/c
> mlst : mlist?
> pos : exact-nonnegative-integer?

Like list-ref, but for mutable lists.

> procedure (mlist-tail mlst pos) → any/c
> mlst : mlist?
> pos : exact-nonnegative-integer?

Like list-tail, but for mutable lists.

> procedure (mappend mlst ...) → mlist?
> mlst : mlist?
> (mappend mlst ... v) → any/c
> mlst : mlist?
> v : any/c

Like append, but for mutable lists.

> procedure (mappend! mlst ...) → mlist?
> mlst : mlist?
> (mappend! mlst ... v) → any/c
> mlst : mlist?
> v : any/c

The mappend! procedure appends the given mutable lists by mutating the tail of each to refer to the next, using set-mcdr!. Empty lists are dropped; in particular, the result of calling mappend! with one or more empty lists is the same as the result of the call with the empty lists removed from the set of arguments.

> procedure (mreverse mlst) → mlist?
> mlst : mlist?

Like reverse, but for mutable lists.

> procedure (mreverse! mlst) → mlist?
> mlst : mlist?

Like mreverse, but destructively reverses the mutable list by using all of the mutable pairs in mlst and changing them with set-mcdr!.

> procedure (mmap proc mlst ...+) → mlist?
> proc : procedure?
> mlst : mlist?

Like map, but for mutable lists.

> procedure (mfor-each proc mlst ...+) → void?
> proc : procedure?
> mlst : mlist?

Like for-each, but for mutable lists.

> procedure (mmember v mlst) → (or/c mlist? #f)
> v : any/c
> mlst : mlist?

Like member, but for mutable lists.

> procedure (mmemv v mlst) → (or/c mlist? #f)
> v : any/c
> mlst : mlist?

Like memv, but for mutable lists.

> procedure (mmemq v mlst) → (or/c list? #f)
> v : any/c
> mlst : mlist?

Like memq, but for mutable lists.

> procedure (massoc v mlst) → (or/c mpair? #f)
> v : any/c
> mlst : (mlistof mpair?)

Like assoc, but for mutable lists of mutable pairs.

> procedure (massv v mlst) → (or/c mpair? #f)
> v : any/c
> mlst : (mlistof mpair?)

Like assv, but for mutable lists of mutable pairs.

> procedure (massq v mlst) → (or/c mpair? #f)
> v : any/c
> mlst : (mlistof mpair?)

Like assq, but for mutable lists of mutable pairs.

> procedure (mlistof pred) → (any/c . -> . boolean?)
> pred : (any/c . -> . any/c)

Returns a procedure that returns #t when given a mutable list for which pred returns a true value for all elements.

(require racket/mpair)

The racket/mpair library re-exports compatibility/mlist for backward compatibility.
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