8.3: Characters

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Page ID: 36374

Andrew P. Black, Stéphane Ducasse, Oscar Nierstrasz, Damien Pollet

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Character is defined in the Collections-Strings category as a subclass of Magnitude. Printable characters are represented in Squeak as $⟨char⟩. For example:

$a < $b    →    true

Non-printing characters can be generated by various class methods. Character class»value: takes the Unicode (or ASCII) integer value as argument and returns the corresponding character. The protocol accessing untypeable characters contains a number of convenience constructor methods such as backspace, cr, escape, euro, space, tab, and so on.

Character space = (Character value: Character space asciiValue)    →    true

The printOn: method is clever enough to know which of the three ways to generate characters offers the most appropriate representation:

Character value: 1    →    Character value: 1
Character value: 32   →    Character space
Character value: 97   →    $a

Various convenient testing methods are built in: isAlphaNumeric, isCharacter, isDigit, isLowercase, isVowel, and so on.

To convert a Character to the string containing just that character, send asString. In this case asString and printString yield different results:

$a asString        →    'a'
$a                 →    $a
$a printString     →    '$a'

Every ascii Character is a unique instance, stored in the class variable CharacterTable:

(Character value: 97) == $a    →    true

Characters outside the range 0 to 255 are not unique, however:

Character characterTable size                        →    256
(Character value: 500) == (Character value: 500)     →    false