Hi,

I'm engaged in a discussion with someone 
(http://stackoverflow.com/questions/3527753) on whether Smalltalk is or 
is not a functional programming language.

Now admittedly no one in the argument has defined what exactly 
checkboxes a language needs to tick to qualify as an FPL. (Also, "Foo 
is/is not a Bar" discussions tend to generate more heat than light.)

So at any rate, my position is that because it's natural and idiomatic 
to program in Smalltalk in a functional way (see Point class and the 
Collection API - #collect:, #select:, #reduce: and friends), yes, 
Smalltalk is a FPL.

I'm not quite sure what position igouy holds. Or, rather, I know that he 
(I'll just use the English male pronouns here for brevity) says that 
Smalltalk's not a FPL, but I'm not sure why. He talks of there being no 
way to define named functions outside of a class as being the reason, 
but I'm sure that can't be all of it. (You can - Smalltalk at : #square 
put: [:x| x * x] - but that's hardly idiomatic.)

At any rate, I've spent a while thinking about the matter, so I'm happy 
either way.

It seems to me that the _real_ reason one might label Smalltalk as not 
being a FPL is mutable state.

You can, with a smidge of discipline, happily write a functional object. 
But it's just as easy to write a mutable object.

Point is a good example of a Value Object (aka "immutable state") as is, 
if I recall correctly, Rectangle: methods either return part of the 
state of an object (0 at 0 x) or, if they're state-mutating, return a new 
object with the required state (0 at 0 translateBy: 1 at 1). There's a mild 
hiccup here, where your "return a new object with new state" must 
initialise the new object. Point does this by having #setX:setY: in the 
'private' category.

But this discipline isn't enforced by the language/environment, which 
for some might be a necessary condition for FPL-ness.

Or have I missed the point of what makes a language an FPL?

frank