Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!haven!mimsy!tove.umd.edu!folta
From: folta@tove.umd.edu (Wayne Folta)
Newsgroups: comp.lang.smalltalk
Subject: Smalltalk (maybe only Smalltalk/V) quest.
Message-ID: <17280@mimsy.UUCP>
Date: 3 May 89 21:48:00 GMT
Sender: nobody@mimsy.UUCP
Reply-To: folta@tove.umd.edu.UUCP (Wayne Folta)
Distribution: usa
Organization: U of Maryland, Dept. of Computer Science, gs
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I just got Smalltalk/V Mac last night, and I was running through the
book that comes with it.  One of their examples does not work, however, and
I wonder if my question is Smalltalk- or Smalltalk/V-specific: it has to do
with Smalltalk/V's Bags class.  Is this a standard class in most Smalltalk
implementations, or is it Smalltalk/V-specific?

As for the question... they give a program in Pascal that counts the
occurrences of letters in an input string.  Then they show the  Pascal-like
Smalltalk code to do the same thing, which is about 25% shorter.  Then,
they give a "native" Smalltalk version, which is only 5 lines:

   |s f|
   s := Prompter prompt: 'enter line' default: ''.
   f := Bag new.
   s do: [:c | c isLetter ifTrue: [f add: c asLowerCase]].
   ^f

It is impressive to see how much more efficient Smalltalk can be, until you
actually evaluate the program.

The problem is that it *does not* result in an array with the number of
occurrences, it results in a Bag containing all of the letters.  One more
step is needed to get the number of occurrences.  What is the most Smalltalk-
like way (if there is such a thing) to accomplish this?  Maybe something like:

   ^'abcdefghijklmnopqrstuvwxyz' collect: [:c | f occurrencesOf: c]

(Which gives me an error which I--novice that I am--don't understand.)


Wayne Folta          (folta@tove.umd.edu  128.8.128.42)