Re: foreach UFCS
On Thursday, 31 March 2016 at 13:48:27 UTC, Adam D. Ruppe wrote: It is trying to look up a name i in global scope, and calling writeln on it. This is why the .name syntax exists: so you can bypass local variables with the same name when trying to access a global. It would compile if you put an `int i;` at the top of your module... try it! Thanks, that makes sense! I had forgotten the global dot syntax. That seems like a somewhat sketchy syntax given how little one would use it, wouldn't something like: writeln(i).global; be much clearer for globals?
Re: foreach UFCS
On Thursday, 31 March 2016 at 13:39:25 UTC, ixid wrote:
What is going on with UFCS and foreach?
foreach(i;0..5).writeln;
This is not UFCS; it is calling writeln on module scope. See
http://dlang.org/spec/module.html#module_scope_operators
Your code is semantically identical with
foreach (i; 0 .. 5)
{
.writeln; // module scope operator!
}
Furthermre because there is no local variable writeln that could
be confused with the imported function, the code is identical with
foreach (i; 0 .. 5)
{
writeln;
}
This prints five line breaks.
foreach(i;0..5).i.writeln;
This will not compile.
It does not compile because i is not an identifier at module
scope. i is a local variable and a hypothetical i at module scope
(accessible via .i) is not declared, therefore this is an error.
foreach(i;0..5).writeln(i);
This writes out 1 to 4 on separate lines. Is this supposed to
work? I thought a.b would be rewritten to b(a) with UFCS but
writeln(foreach(i;0..5)) is nonsensical and does not compile
and should be the same as foreach(i;0..5).writeln;
It does rewrite. But only if there is an expression beforehand
the dot. Here it just isn't. The "foreach (i; 0 .. 5)" is not a
complete expression.
Re: foreach UFCS
On Thursday, 31 March 2016 at 13:39:25 UTC, ixid wrote:
What is going on with UFCS and foreach?
There's no such thing as UFCS on foreach. UFCS only works on
variables, not a foreach statement.
foreach(i;0..5).writeln;
You can add a line break and optional braces there to see what it
really is:
foreach(i;0..5) {
.writeln;
}
It is just an ordinary loop calling writeln 5 times. The leading
dot in D means "look up in the global namespace".
foreach(i;0..5).i.writeln;
foreach(i; 0 .. 5) {
.i.writeln;
}
It is trying to look up a name i in global scope, and calling
writeln on it.
This is why the .name syntax exists: so you can bypass local
variables with the same name when trying to access a global.
It would compile if you put an `int i;` at the top of your
module... try it!
foreach(i;0..5).writeln(i);
foreach(i; 0 .. 5) {
.writeln(i); // leading . just means call global writeln
}
What you're seeing is similar to the Java hoax where people say
it supports hyperlinking:
public static void main() {
http://dlang.org/awesome
}
That compiles, but it isn't a link, it just looks like one at
first.
It is actually a label, "http:", followed by a comment,
"//dlang.org". Two legal things without whitespace that looks
like something else at first glance.
Re: foreach UFCS
On Thursday, 31 March 2016 at 13:39:25 UTC, ixid wrote:
What is going on with UFCS and foreach?
foreach(i;0..5).writeln;
This prints five line breaks.
foreach(i;0..5).i.writeln;
This will not compile.
foreach(i;0..5).writeln(i);
This writes out 1 to 4 on separate lines. Is this supposed to
work? I thought a.b would be rewritten to b(a) with UFCS but
writeln(foreach(i;0..5)) is nonsensical and does not compile
and should be the same as foreach(i;0..5).writeln;
The compiler interprets it as a foreach without curly braces.
With curlies it would look like:
foreach(i; 0..5)
{
.writeln();
}
In this context the dot means the writeln lookup should happen
from the module level scope.
foreach UFCS
What is going on with UFCS and foreach? foreach(i;0..5).writeln; This prints five line breaks. foreach(i;0..5).i.writeln; This will not compile. foreach(i;0..5).writeln(i); This writes out 1 to 4 on separate lines. Is this supposed to work? I thought a.b would be rewritten to b(a) with UFCS but writeln(foreach(i;0..5)) is nonsensical and does not compile and should be the same as foreach(i;0..5).writeln;
