From: Tom Cloyd <tomcloyd@...>
Date: 2009-02-01T06:16:56+09:00
Subject: Re: proper use of classes

Robert Klemme wrote:
> On 31.01.2009 10:02, Tom Cloyd wrote:
>> BTW, I was puzzled for years by the mathematical notion of a 
>> function. It just eluded me. Baffled me. Then, as I was learning to 
>> program in Fortran, years ago, I began to wonder if there was any 
>> relation between Fortran functions (hope you know a little Fortran) 
>> and mathematical functions. Of course, there is. Fortran functions 
>> was no problem at all to grasp, and once I realized they were just 
>> another way of expressing a mathematical function (or perhaps I 
>> should say that a math function can be expressed as a Fortran 
>> function, and in fact that was what they were for), I was seriously 
>> rageful.
>
> IMHO there is an important distinction though which makes Fortran 
> functions a bad example: mathematical functions usually do not have 
> side effects, i.e. they can be completely described in terms of input 
> and output.  I view them as a relationship (or call it a mapping) 
> which assigns particular output values to particular input values.  If 
> I'm not mistaken, a Fortran function can have side effects on 
> arguments (and probably global variables).  A closer analogy are 
> functions in - you guessed it - functional languages.
>
> Kind regards
>
>     robert
>
>
Robert - I absolutely agree, and I can to that (or THOSE) 
understanding(s) in my first pass through grad. school. The idea of a 
function being a rule that associates two sets of numbers seems to me 
the most useful. However, the initial breakthrough for me was to see a 
function as a little program - a process: put something in, get 
something out. So easy. For some reason, that view it escaped me 
throughout high school, etc. (I was a writer, not a calculator!).

Thanks for your thoughts, as always. I always enjoy what you have to say!

Tom

-- 

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Tom Cloyd, MS MA, LMHC - Private practice Psychotherapist
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