Ranges, constantly frustrating

[bearophile]

Regan Heath:

> FWIW I disagree.  I think it's immediately and intuitively 
> obvious what 'i' should be when you're foreaching over X items 
> taken from another range, even if you do not know take returns 
> another range.  Compare it to calling a function on a range and 
> foreaching on the result, you would intuitively and immediately 
> expect 'i' to relate to the result, not the input.

Using enumerate has several advantages. It gives a bit longer 
code, but it keeps as much complexity as possible out of the 
language. So the language gets simpler to implement and its 
compiler is smaller and simpler to debug.

Also, using enumerate is more explicit, if you have an 
associative array you can iterate it in many ways:

foreach (v; AA) {}
foreach (k, v; AA) {}
foreach (k; AA.byKeys) {}
foreach (i, k; AA.byKeys.enumerate) {}
foreach (i, v; AA.byValues.enumerate) {}
foreach (k, v; AA.byPairs) {}
foreach (i, k, v; AA.byPairs.enumerate) {}

If you want all those schemes built in a language (and to use 
them without adding .enumerate) you risk making a mess. In this 
case "explicit is better than implicit".

Python does the same with its enumerate function and keeps the 
for loop simple:

for k in my_dict: pass
for i, v in enumerate(my_dict.itervalues()): pass
etc.

In D we have a mess because tuples are not built-in. Instead of 
having a built-in functionality similar to what enumerate does, 
it's WAY better to have built-in tuples. Finding what's important 
and what is not important to have as built-ins in a language is 
an essential and subtle design problem.

Bye,
bearophile