[Issue 15285] Range-ified functions for std.string

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15285

--- Comment #4 from greenify <greeenify at gmail.com> ---
Hey I had a look at what types does functions allow:

abbrev          string[]
capitalize      isSomeString
isNumeric       isSomeString
inPattern       isSomeString
munch           isSomeString  
representation  Char[] (char[],wchar[],dchar[])
squeeze         anything - no constrains???
succ            isSomeString
translate       immutable char[]
outdent         isSomeString
wrap            isSomeString

I guess the biggest win is, if we first focus on those isSomeString functions.

So you mean we could add to isSomeString a RangeString?

```
template isRangeString(R)
{
    enum bool isRangeString = is(typeof(
    (inout int = 0)
    {
        static assert(isInputRange!R);
        static assert(hasLength!R); // all the algorithms allocate a new
immutable string
        static asssert(isSomeChar!(isElementType!R));
    }
}
```

The only problem then would be that currently those algorithms use an
index-based for-loop

```
    for (size_t i = j; i < iLen; i++)
    {
        immutable c = s[i];
```

can we just replace that with 

```
   foreach (i,immutable c;s)
```

so in summary - my questions:

1) can we replace for --> foreach or do we have to use `static if`?
2) we still will return a newly allocated immutable string. Should we return
something different for ranges?

--