foreach with a default range

[w0rp via Digitalmars-d]

A thought just came to me. When I'm implementing foreach for a 
container, I'm left with the choice of using a range for a 
container or opApply. I've found often that I prefer the ranges, 
as it's easy for me to write a range that satisfies @nogc @safe 
pure nothrow, etc. This is because the ranges don't call 
delegates which are less restrictive, which opApply does.

I've been thinking about how you would implement opApply so that 
it could allow you to run @system code while the iteration itself 
is @safe, but then I had another idea. Could we allow foreach to 
look for a method (UFCS include) for producing a default range 
for an object, from a function named 'range'?

In short this...

foreach(elem; container) {}

Could be transformed into this.

foreach(elem; container.range()) {}

This is not too different from how iteration works in Python, 
Java, etc. The objects are asked for an iterator, and the 
iterator is used to iterate through the object. This would allow 
you to implement ranges with more qualifiers set on them, without 
having to type .range() everywhere.

What do others think?