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MIT Scheme implements strings as packed vectors of 8-bit ASCII
bytes. Most of the string operations, such as string-ref, coerce
these 8-bit codes into character objects. However, some lower-level
operations are made available for use.
procedure+: vector-8b-ref string k
Returns character k of string as an ASCII code. K must be a valid index of string.
(vector-8b-ref "abcde" 2) => 99 ; ascii for `c'
procedure+: vector-8b-set! string k ascii
Stores ascii in element k of string and returns an unspecified value. K must be a valid index of string, and ascii must be a valid ASCII code.
procedure+: vector-8b-fill! string start end ascii
Stores ascii in elements start (inclusive) to end (exclusive) of string and returns an unspecified value. Ascii must be a valid ASCII code.
procedure+: vector-8b-find-next-char string start end ascii
procedure+: vector-8b-find-next-char-ci string start end ascii
Returns the index of the first occurrence of ascii in the given
substring; returns #f if ascii does not appear. The index
returned is relative to the entire string, not just the substring.
Ascii must be a valid ASCII code.
vector-8b-find-next-char-ci doesn't distinguish uppercase and
lowercase letters.
procedure+: vector-8b-find-previous-char string start end ascii
procedure+: vector-8b-find-previous-char-ci string start end ascii
Returns the index of the last occurrence of ascii in the given
substring; returns #f if ascii does not appear. The index
returned is relative to the entire string, not just the substring.
Ascii must be a valid ASCII code.
vector-8b-find-previous-char-ci doesn't distinguish uppercase and
lowercase letters.
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