Re^3: Unhappy returns

[Perl Mouse]

Well, map and grep are usually seen as functions, but there's no denying that both map and grep are looping constructs.

But ultimely, what is the difference between an operator, a function or a syntax construct from a programmers aspect of view (other than using it to answer "where do I find this in the manual")? Would you code differently if map or grep were reclassified as a syntax or looping construct, or foreach as a function?

[Aristotle]

The difference is that foreach is a statement, and as such does not return anything. The context in which its body is evaluated is therefore never of any interest, any more than it is of interest which context the body of an if or while is evaluated in.

map and grep OTOH are expressions and do return something; which means context is paramount.

[ysth]

I'd have to disagree. Every runtime statement in perl does have a return value. It's not true that foreach doesn't return anything. Ponder this piece of code:

@x = sub { 0; for (4,3,2) { 1 } }->();

What does the sub return? Is it a bug? What should it return? (It has to return something, even if it's an empty list.) Also compare to

@x = sub { }->();

and

$x = sub { 0; for (4,3,2) { 1 } }->();

[Aristotle]

What does the sub return?

The foreach in your examples is a red herring. A function call is an expression. And function calls return the value of the last expression evaluated. foreach is not an expression, but in the course of its execution several of those may be evaluated.

My statement stands. (Pun intended.)

[sauoq]

It's not true that foreach doesn't return anything.

Sure it is. Otherwise, you would not have had to wrap your example for loops in a sub to try to make your point. If it returned something, you'd be able to write code like: @x = for (1) { 1 }; But, that's a syntax error. Why? Because statements don't return anything. Q.E.D.