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Comment by zabzonk | Hacker News Reader

apart from that (which i agree with) is that in most pascal-like languages you have to define variables at the top of a function, and their scope is the whole function. both c (nowadays, define at top of a {} scope) and c++ (define anywhere inside a function) do much better which, together with irritating long names, may explain why c and c++ won out over the pascal-likes.

speaking as an ex professional delphi programmer here - i have written lots of object pascal code, and have no desire to write any more.

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C is declare anywhere and has been for a looong time (C99).

sorry, my bad, i don't do any c programming these days.

but to be pedantic, i think you mean define rather than declare, though of course you can also declare things at different scopes.

No, I think they do mean declare. In C89 you can define a variable anywhere, like so:

    int x;
    f();
    x=3;

The improvement was allowing declarations anywhere.

Isn't the first row both the declaration and definition is this case?

(I assume f() is a call.)

C (and C++) considers the declaration to be separate from the definition, though you can combine them. The declaration is the name + type, definition provides a value. The example code is meant to illustrate separate declaration and definition with some code (the call to `f`) between the two.

If you try to use `x` before it is defined (the assignment) your compiler should give you a warning, at least. If it doesn't, find a new compiler.

For block-scope declarations, it's not the definition but the initialization that you're thinking of. At least in C, every block-scope variable declaration is a definition:

> A definition of an identifier is a declaration for that identifier that:

> — for an object, causes storage to be reserved for that object; [...]

But initialization (in C) does not occur for block-scope objects without the optional initializer.

Okay, that's somewhat confusing. So a declaration is when the identifier enters the scope, and a definition is for a variable specifically. So a declaration that's not a definition could be a forward declaration for a function, or a typedef.

Yes, or the declaration of an extern variable.

Delphi supports local variable declarations for quite some years now, and Ada does it since its introduction in 1983.

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