Variables

[Bengt Richter]

On Sat, 23 Apr 2005 22:45:14 -0400, Richard Blackwood <richardblackwood at cloudthunder.com> wrote:

>Robert Kern wrote:
>
>> Richard Blackwood wrote:
>>
>>> To All:
>>>
>>>    Folks, I need your help. I have a friend who claims that if I write:
>>>
>>> foo = 5
>>>
>>> then foo is NOT a variable, necessarily. If you guys can define for 
>>> me what a variable is and what qualifications you have to back you, I 
>>> can pass this along to, hopefully, convince him that foo is indeed a 
>>> variable.
>>
>>
>> None of us can do that unless you tell us what he thinks the word 
>> "variable" means. The terminology is a bit fluid. I suspect that your 
>> friend applying a somewhat restricted notion of "variable" that 
>> coincides with the behavior of variables in some other language.
>>
>Indeed, this language is math. My friend says that foo is a constant and 
>necessarily not a variable. If I had written foo = raw_input(), he would 
>say that foo is a variable. Which is perfectly fine except that he 
>insists that since programming came from math, the concept of variable 
>is necessarily the identical. This can not be true. For example, I may 
>define foo as being a dictionary, but I can not do this within math 
>because there is no concept of dictionaries within mathematics; yet foo 
>is a variable, a name bound to a value which can change.

Maybe he doesn't know that foo = 5 in Python is not an equation as in math,
but a Python source language statement to be translated to a step in some
processing sequence.

Tell him in Python foo is a member of one set and 5 is a member of another,
and foo = 5 expresses the step of putting them into correspondence
to define a mapping, not declaring them equal.

Even in math notation, ISTM important to distinguish between
a finger and what it may for the moment be pointing at.

Regards,
Bengt Richter