Computer Programming with GNU Smalltalk - Free

setNumerator:setDenominator:
Objects, Messages and Classes: Part I 31
To set the numerator and the denominator of a fraction, we use setNumerator:setDenominator
message:
3/4 setNumerator: 5 setDenominator: 6
5/6
Note that, this time we didn't need to use parenthesis because this time we send a keyword message to
the expression 3/4 and binary messages already have a precedence over keyword messages.
Character
Characters are the single symbols we use to represent data. For example; letters, special characters like
%, and digits like 9 are all characters. They are individual objects in Smalltalk. Though, to tell Smalltalk
environment that we want to treat a symbol as a character, we have to put a $ (dollar sign) in front of it.
For example:
$a
$%
$9
And we use the same methodology to represent dollar sign itself:
$$
We have a lot of methods to apply on characters, some of which are mentioned below.
asLowercase
If you have a letter to convert into lowercase then you can use asLowercase message:
$D asLowercase
$d
asUppercase
Uppercase counterpart of asLowercase is asUppercase.
$d asUppercase
$D
isAlphaNumeric
If you have a suspicion whether a symbol is alphanumeric, then you can use isAlphaNumeric
message:
$% isAlphaNumeric