So my problem is the following:
When char = 0
boolean = char ~= 0 & char ~= 256
evaluates to true and if I invert the statements like so:
boolean = char ~= 256 & char ~= 0
I get false.
What's happening?. I am expecting false on both cases.
As @Uko said, you must understand the precedence of messages: all binary messages (+ = < & ~= etc..) are evaluated from left to right.
Thus you evaluate:
(((boolean = char) ~= 256) & char) ~= 0
I think you were after:
boolean := (char ~= 256) & (char ~= 0).
So what happens with your expression ?
booleanis presumably unitialized (thus nil)char is 0.boolean = char is false.false ~= 256 is true.true & char is char (see below why)char ~= 0 is false (since char = 0)If you invert 0 and 256, only the last step changes and awnswer true.
The interesting part is the implementation of message & in class True: it probably does not assert that the parameter is a Boolean and looks like:
& aBoolean
^aBoolean
If you pass something that is not a Boolean, (like 0 in your case), it will return this thing, whatever surprising it can be...
If you use an IDE (Squeak/Pharo/Visualworks/Dolphin... but not gnu Smalltalk) I suggest you use the menu Debug It and evaluate the expression step by step in the Debugger.
Last, note that char is probably not a good name in Smalltalk context: it might be misleading. Indeed, if it holds 0, it's rather an Integer, not a Character.