Have you tried stepping through this with the debugger? Below some ideas to help you solving problems like this the next time (how to set breakpoints, have breakpoints with comment and do conditional breakpoints). If you already know this, then it always might help someone else :-)

For example, add a breakpoint by sending a 'halt' message to any kind of object. Then you can step and send through this piece of code to see what exactly goes on:

self do: [:element | self halt. element number == accountNumber ifTrue:([Transcript show: element;cr]) ifFalse:([Transcript show: 'No such account exists in this portfolio';cr])].

You will see that the message == gets send and what it does. Note that you can accept new code while you go along, and it will immediately take tis into account. Try it to believe it :-)

Note also that you can use 'halt:' and give a string argument that will be shown when the breakpoints pops up. For example the following will pop up the current number it needs to compare. That way you can decide whether to do 'proceed' or 'debug' more easily:

self do: [:element | self halt: element printString. element number == accountNumber ifTrue:([Transcript show: element;cr]) ifFalse:([Transcript show: 'No such account exists in this portfolio';cr])].

You can easily set conditional breakpoints, since it is just plain Smalltalk code. For example, you might only want to see the cases when numbers are negative like this:

self do: [:element | (element < 0) ifTrue: [self halt: element printString]. element number == accountNumber ifTrue:([Transcript show: element;cr]) ifFalse:([Transcript show: 'No such account exists in this portfolio';cr])].

With the same mechanism you can pop up the debugger when a certain key is pressed (so that you can let it crunch for a while before going in to inspect the code. I do not know the exact expression in Squeak, but somebody else will be able to help you there. In VisualWorks (another Smalltalk environment) you would say: InputState default shiftDown ifTrue: [self halt].

Hope this helps a bit. But I am pretty sure (like Avi was) that you want to compare using #= in this case. Almost all of the time you want to do that, actually, unless you are really looking for a particular object, and only want that object.

On Monday, February 3, 2003, at 05:44 AM, Janet Abdul-Karim wrote:

I am understanding what you said about the difference between #= and #==, but I still get the same result. I am wondering is my logic somehow work or could I possibly be missing some type of punctuation because I know the object is there but it seems to always evaluate the false part and then prints out the type of the object that i am looking for.

Avi Bryant avi@beta4.com wrote:

On Sun, 2 Feb 2003, Janet Abdul-Karim wrote:

...

I am trying to find a certain value in a collection. does something

if true or does something if false and for some reason it always evaluates to false and I know its there. Any help would be great

...

sample code.

findAccount: accountNumber "Find the account with the argument number"

self do:[:element | element number == accountNumber ifTrue:([Transcript show: element;cr]) ifFalse:([Transcript show: 'No such account exists in this

portfolio';cr])].

My guess is that you want to use #= (equality) not #== (identity equality). Numbers above a certain size are represented in such a way that they are not the same object even when they are the same number, and so they are #= but not #==. For example:

12 = 12 "true" 12 == 12 "true" (12 raisedTo: 10) = (12 raisedTo: Yahoo! Mail Plus - Powerful. Affordable. Sign up now

Roel Wuyts Software Composition Group roel.wuyts@iam.unibe.ch University of Bern, Switzerland http://www.iam.unibe.ch/~wuyts/ Board Member of the European Smalltalk User Group: www.esug.org

Hi Janet,

I think your mistake lies in what you expect to happen. The comparison wil be evaluated for every element in the collection and thus the transcipt will tell you (n-1) times that the element is not in the collection (where n is the number of elements in the collection) and only once will show the element.

To make it clearer i'd change the code to: (assuming you do this in an inspector where self is bound to the collection) self do:[:element | element number == accountNumber ifTrue:([Transcript show: element;cr]) ifFalse:([Transcript show: element, ' is not the desired element';cr])].

Of course you could also write: Transcript show: (self detect:[:element | element number == accountNumber] ifNone:['no such element']).

HTH, Torge

03.02.2003 05:44:13, Janet Abdul-Karim jn_karim@yahoo.com wrote:

...

findAccount: accountNumber "Find the account with the argument number"

self do:[:element | element number == accountNumber ifTrue:([Transcript show: element;cr]) ifFalse:([Transcript show: 'No such account exists in this

portfolio';cr])].

My guess is that you want to use #= (equality) not #== (identity equality). Numbers above a certain size are represented in such a way that they are not the same object even when they are the same number, and so they are #= but not #==. For example:

12 = 12 "true" 12 == 12 "true" (12 raisedTo: 10) = (12 raisedTo: 10) "true" (12 raisedTo: 10) == (12 raisedTo: 10) "false"

Avi

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