Variables

[Ron]

Richard Blackwood wrote:

> He would argue strongly against your notion of variable. In the 
> statement "foo = 5", foo is constant. He would thus argue that foo is a 
> constant and not a variable (regardless of whether you change foo's 
> value in subsequent statements).

Sounds like his mind is made up and you will probably not be able to 
persuade him otherwise.

But maybe this will help... or not. ;-)

Given a math equation...

x = 2y+3

x and y are clearly (most would agree) variables.  The value of each 
changes depending on the value of the other.

To solve the equation you set one variable to a value to find the other.

x = 2*y+3
y = 5

x = 2*5+3
x = 13

Do this again for other values... etc...

Would he agree that x, and y are variables even after a value is 
determined?  Or would he say that they become constants once you decide 
a value for one?

I think context is the deciding factor if this is a general discussion 
concerning math equations.  The above equation may be an equation of a 
line, or it may be the equation of a specific condition with two unknowns.

They may variables which may either have the value which is constant, a 
known value, an unknown value, or a range of values.

So given only "foo = 5" ...

In Python foo is a Name which is bound to the integer 5.  There are 
other way to describe it, but it all comes down to being symbols 
representing a concept.

(It could have been a randomly generated sequence with no meaning at all 
too!)

Without knowing the context of the discussion, that is all that we can 
say.  However if we were to agree that foo represents a concept that has 
an unchanging value in the context that it is used, then it is a 
constant, because we agreed that it is.  So it is determined by the 
meaning we agree (or decide for ourself) to give to the name "foo".

So what is the meaning of foo?  In general computer discussions foo is 
ever changing and represents an abstract object to be used and reused to 
describe a multitude of possibilities.  I would call that a variable.

  ;-)

Cheers,
Ron