On 30/09/2016 15:01, Chris Angelico wrote:
On Fri, Sep 30, 2016 at 10:33 PM, Steve D'Aprano
<steve+pyt...@pearwood.info> wrote:
To me, "make for-loops be their own scope" sounds like a joke feature out of
joke languages like INTERCAL. I'm not aware of any sensible language that
does anything like this.
No, wait a minute, I tell a lie, I recall Chris Angelico mentioning that one
of his favourite languages, Pike or REXX, does it. I forget which.
In C-like languages (including Pike), you can legally define a
variable at any point, making it visible at that point and all inner
locations - effectively, every brace becomes a new subscope. It makes
sense ONLY because variables are declared, no matter where they are
(globals are declared at module scope, locals at some kind of inner
scope). So, it's not strictly true that Pike has for loops as their
own scope, just that C-like languages have a lot of nested scopes.
C likes to make things a bit more complicated:
int A;
{ A; // this is the outer A
int A;
A; // this is the inner A
goto A;
A: // this is yet another A
}
Labels live in a different name-space from other names. I've left out
struct tags which also have their own name-space, and would allow five
different A's in that block (an outer and inner 'struct A') rather than
the three I've shown.
So a single pair of {-} can enclose three (sometimes five) versions of
the same identifier.
Personally I think function-scope is plenty. Only one possible top-level
'A' in a function instead of an unlimited number.
(Python allows extra 'A's inside nested functions and classes within
that function, but that's a bit different.)
--
Bartc
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