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The module Char contains procedures operating on characters. Characters are integers between 0 and 255, used for building strings. For the encoding of characters by integers, we use the ISO 8859-1 standard [ISO87]. The functionality provided by this module is similar to the ctype.h module of ANSI C, see for instance [KR88].
The procedures described herein can be used to compute with strings by using the generic procedures of the list module (see Section 6.3). For example,
{Filter "r E!m O\nv7E" Char.isAlpha} keeps only the letters of the given string and returns the string "rEmOvE".
IsChar
{Char.is+X?B}
tests whether X is a character, i. e., an integer between 0 and 255 inclusively.
isLower
{Char.isLower+Char?B}
tests whether Char encodes a lower-case letter.
isUpper
{Char.isUpper+Char?B}
tests whether Char encodes an upper-case letter.
isDigit
{Char.isDigit+Char?B}
tests whether Char encodes a digit.
isSpace
{Char.isSpace+Char?B}
tests whether Char encodes a white space character, i. e., either a space, a form feed (&\f), a newline (&\n), a carriage return (&\r), a tab (&\t), a vertical tab (&\v) or a non-breaking space (&\240).
isPunct
{Char.isPunct+Char?B}
tests whether Char encodes a punctuation character, i. e., a visible character, which is not a space, a digit, or a letter.
isCntrl
{Char.isCntrl+Char?B}
tests whether Char encodes a control character.
isAlpha
{Char.isAlpha+Char?B}
tests whether Char encodes a letter.
isAlNum
{Char.isAlNum+Char?B}
tests whether Char encodes a letter or a digit.
isGraph
{Char.isGraph+Char?B}
tests whether Char encodes a visible character.
isPrint
{Char.isPrint+Char?B}
tests whether Char is a visible character or either the space or non-breaking space character.
isXDigit
{Char.isXDigit+Char?B}
tests whether Char is a hexadecimal digit.
type
{Char.type+Char?A}
maps Char to its simple type A, i. e., one of the atoms lower, upper, digit, space, punct, or other.
toLower
{Char.toLower+Char1?Char2}
returns the corresponding lower-case letter if Char1 is an upper-case letter, otherwise Char1 itself.
toUpper
{Char.toUpper+Char1?Char2}
returns the corresponding upper-case letter if Char1 is a lower-case letter, otherwise Char1 itself.
toAtom
{Char.toAtom+Char?A}
maps Char to the corresponding atom A. If Char is zero, A will be the empty atom ''.
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