Re: Need help: Return reference slice

[Ali Çehreli via Digitalmars-d-learn]

On 10/29/2014 12:50 PM, advibm wrote:

Hello,

I would like to create a D function that returns a slice of a string.
This slice shall be a reference to a part of the string argument.
Is this generally possible in D?

This is the function:
auto ref betweenTwoStrings(T)(inout T src, string start, string end) {
   long a = src.countUntil(start);
   if (a < 0)
     return src; // null
   a += start.length;
   long b = src[a..$].countUntil(end);
   if (b < 0)
     return src; // null
   b += a;
   return src[a..b];
}


I would like to have something like that:

char[] buf; // already filled array
char[] partOfBuf = betweenTwoStrings(buf, "START", "END");
partOfBuf[0] = 'a'; // THIS should also change the 'buf' variable
assert(buf[0] == 'a');

Thanks for your help

There are pretty useful std.algorithm functions for searching:

import std.algorithm;
import std.traits;
import std.array;

C[] betweenTwoStrings(C)(C[] src, string start, string end)
    if (isSomeChar!C)
{
    if (src.findSkip(start)) {
        auto found = src.findSplitBefore(end);

        // Just for readability:
        auto needleAndAfter = found[1];

        if (!needleAndAfter.empty) {
            auto beforeNeedle = found[0];
            return beforeNeedle;
        }
    }

    return (C[]).init;
}

void main()
{
    char[] buf;
    buf ~= "prefixSTARTactual partENDpostfix";

    char[] partOfBuf = betweenTwoStrings(buf, "START", "END");

    partOfBuf[] = 'a';
    assert(buf == "prefixSTARTaaaaaaaaaaaENDpostfix");
}

Ali