CODEWITHSUNDEEP
smalltalksqueak
parsifal
parsifal

Reputation: 917

How do I debug Squeak source code?

Here is the division method in Squeak 4.1:

/t1
| t2 |
t1 isInteger
    ifTrue: [t2 := self digitDiv: t1 abs neg: self negative ~~ t1 negative.
        (t2 at: 2)
                = 0
            ifTrue: [^ (t2 at: 1) normalize].
        ^ (Fraction numerator: self denominator: t1) reduced].
^ t1 adaptToInteger: self andSend: #/

I do not understand the code. Can you give me some hints on how to debug the code, so I can trace the code behavior? Like open a workspace, type 4/3, I can inspect into Fraction. There are objects self, numerator, denominator and etc. How can I step into 4/3, and see how Smalltalk implemented division?

Upvotes: 1

Views: 521

Answers (1)

codefrau
codefrau

Reputation: 4623

First of all, something is wrong with your sources. The method Integer>>/ actually looks like this:

/ aNumber
"Refer to the comment in Number / "
| quoRem |
aNumber isInteger ifTrue:
    [quoRem := self digitDiv: aNumber abs   "*****I've added abs here*****"
                    neg: self negative ~~ aNumber negative.
    (quoRem at: 2) = 0
        ifTrue: [^ (quoRem at: 1) normalize]
        ifFalse: [^ (Fraction numerator: self denominator: aNumber) reduced]].
^ aNumber adaptToInteger: self andSend: #/

Secondly, this code is only used for large integers. If you evaluate 4 / 3 this method is not used, but rather SmallInteger>>/ which creates a Fraction directly.

To invoke the method you want, you need to use a large number, e.g.:

12345678901234567890 / 2

Select this expression, and choose "debug it" from the context menu. Alternatively, you can use the "halt" message to invoke the debugger:

12345678901234567890 halt / 2

When the debugger pops up, click its "Into" button to step into the method.

Upvotes: 6

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