Origin of the term "first-class object"

[Rainer Deyke]

Ben Finney wrote:
> On Tue, 18 Nov 2003 03:01:35 GMT, Rainer Deyke wrote:
>> One would be passing a name as an argument
>> to a function.
>
> To accomplish what?  What would you be doing with the name that you
> can't do just as easily by passing the object (by reference, as always
> happens in Python)?

Binding the name to a different object.

>> Given the immutability of certain Python objects, it is
>> often necessary to write statements in the form of
>> "x = f(x)".
>
> I don't understand the logic here.  What is it that necessitates
> "x = f(x)",

For example, any "mutating" operation on x, where x is an immutable object.

Trivial and useless example:

def increment(x):
  return x + 1

i = increment(i)

> and why is that undesirable?

Suppose the 'x' in 'x = f(x)' is not a simple variable, but an element in a
list

l[x * 2 + f(y)] = f(l[x * 2 + f(y)])

This statement contains an obvious redundancy that will make code
maintenance difficult.  Python allows me to factor out some of the
redundancy:

index = x * 2 + f(y)
l[index] = f(l[index])

However, Python gives me no way to factor out the remaining redundancy.


-- 
Rainer Deyke - rainerd at eldwood.com - http://eldwood.com