Re: Manipulate slice or specific element of range and return range

[Ali Çehreli via Digitalmars-d-learn]

On 03/21/2018 04:30 AM, Timoses wrote:

Hey,

I'm struggling to find a way to achieve this. I've looked through std.algorithm but didn't find anything.. Maybe I'm blind.

What I would like to do is filter out all spaces in a string and change the front letter to lower case:

     string m = "My Capital String";
     string lower = m
         .filter!(c => c != ' ')
         .<executeAt>!(0, c => c.toLower) // executeAt does not exist
         .array.to!string;
     assert(lower == "myCapitalString");

or sth like

     m.filter!(...)
         .map!((element, int index) {
             if (index == 0)
                 return element.toLower;
             else
                 break; // stop since we are done manipulating range
         });

Anyway to do this?

Here is another one that uses ForwardRange.

import std.range; // empty, take, save, chain, popFrontN;
import std.uni; // asLowerCase;
import std.algorithm; // equal, filter;
import std.conv; // text;

auto initialLowerCased(R)(R str, size_t N = 1) {
    if (str.empty) {
        N = 0;
    }
    auto frontPart = str.take(N);
    auto rest = str.save;
    rest.popFrontN(N);

    return chain(frontPart.asLowerCase, rest);
}

unittest {
    assert(initialLowerCased("My Test String", 4).equal("my test String"));
    assert(initialLowerCased("").equal(""));
}

auto foo(R)(R str) {
    return str.filter!(c => c != ' ').initialLowerCased;
}

void main() {
    auto result = foo("My Capital String");
    // result above is a range. std.conv.text can make a string:
    string lower = result.text;
    assert(lower == "myCapitalString");
}

Ali