liblouis: Character-Class Opcodes
1
1 2.9 Character-Class Opcodes
1 ===========================
1
1 These opcodes define and use character classes. A character class
1 associates a set of characters with a name. The name then refers to any
1 character within the class. A character may belong to more than one
1 class.
1
1 The basic character classes correspond to the character definition
11 opcodes, with the exception of the 'uplow' opcode (⇒uplow uplow
opcode.), which defines characters belonging to the two classes
1 'uppercase' and 'lowercase'. These classes are:
1
1 'space'
1 Whitespace characters such as blank and tab
1 'digit'
1 Numeric characters
1 'letter'
1 Both uppercase and lowercase alphabetic characters
1 'lowercase'
1 Lowercase alphabetic characters
1 'uppercase'
1 Uppercase alphabetic characters
1 'punctuation'
1 Punctuation marks
1 'sign'
1 Signs such as percent ('%')
1 'math'
1 Mathematical symbols
1 'litdigit'
1 Literary digit
1 'undefined'
1 Not properly defined
1
1 The opcodes which define and use character classes are shown below.
1 For examples see 'fr-abrege.ctb'.
1
1 'class name characters'
1 Define a new character class. The characters operand must be
1 specified as a string. A character class may not be used until it
1 has been defined.
1
1 'after class opcode ...'
1 The specified opcode is further constrained in that the matched
1 character sequence must be immediately preceded by a character
1 belonging to the specified class. If this opcode is used more than
1 once on the same line then the union of the characters in all the
1 classes is used.
1
1 'before class opcode ...'
1 The specified opcode is further constrained in that the matched
1 character sequence must be immediately followed by a character
1 belonging to the specified class. If this opcode is used more than
1 once on the same line then the union of the characters in all the
1 classes is used.
1