On Friday, 4 December 2015 at 01:10:41 UTC, Jim Barnett wrote:
Really? If it leads to "hard to detect errors", I have a hard
time believing that can be "idiomatic D".
It's used throughout the standard library, granted I don't think
there's any occurrences of importing inside a while loop. The
issues with nested imports are well known but also hard to fix
without breaking code. However, they cut down on template bloat
and the standard library makes very heavy use of templates. Thus
a tradeoff is made. It's usually not nested imports by themselves
that create these hard to detect errors, however. It's a few
different D features working in concert.
Observe the following code:
struct Test
{
int num = 1;
string text = `"this is a line of text"`;
void printMessage()
{
import std.conv, std.stdio;
writeln(text("My text is ", text, " and my num is ", num));
}
}
void main()
{
Test t;
t.printMessage();
}
It prints: "My text is and my num is 0"
Why the empty space? Because instead of referring to this.text
inside of the printMessage method, `text` refers to
std.conv.text. The nested import overrides the member variable in
the outer scope.
I have never seen a language that encourages the user to
specify dependencies inside a loop. I am hoping I misunderstood
something here.
Sorry, I thought you were referring more generally to nested
imports. No, imports in a while loop are not encouraged; imports
in a struct or a template are.
