46 lines
1.7 KiB
Racket
46 lines
1.7 KiB
Racket
#lang scribble/doc
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@(require scribble/manual scribble/eval "guide-utils.rkt")
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@title[#:tag "vectors"]{Vectors}
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A @deftech{vector} is a fixed-length array of arbitrary
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values. Unlike a list, a vector supports constant-time access and
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update of its elements.
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A vector prints similar to a list---as a parenthesized sequence of its
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elements---but a vector is prefixed with @litchar{#} after
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@litchar{'}, or it uses @racketresult[vector] if one of its elements
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cannot be expressed with @racket[quote].
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For a vector as an expression, an optional length can be
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supplied. Also, a vector as an expression implicitly @racket[quote]s
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the forms for its content, which means that identifiers and
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parenthesized forms in a vector constant represent symbols and lists.
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@refdetails/gory["parse-vector"]{the syntax of vectors}
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@examples[
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(eval:alts @#,racketvalfont{#("a" "b" "c")} #("a" "b" "c"))
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(eval:alts @#,racketvalfont{#(name (that tune))} #(name (that tune)))
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(eval:alts @#,racketvalfont{#4(baldwin bruce)} #4(baldwin bruce))
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(vector-ref #("a" "b" "c") 1)
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(vector-ref #(name (that tune)) 1)
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]
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Like strings, a vector is either mutable or immutable, and vectors
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written directly as expressions are immutable.
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Vectors can be converted to lists and vice versa via
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@racket[vector->list] and @racket[list->vector]; such conversions are
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particularly useful in combination with predefined procedures on
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lists. When allocating extra lists seems too expensive, consider
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using looping forms like @racket[for/fold], which recognize vectors as
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well as lists.
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@examples[
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(list->vector (map string-titlecase
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(vector->list #("three" "blind" "mice"))))
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]
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@refdetails["vectors"]{vectors and vector procedures}
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