In some languages (e.g. python), the string "strip" function family accepts an optional parameter which specifies the set of characters one wants to strip. If not given, this is "whitespace". I think this is very useful and the D strip should support that too.

For example, I needed it when getting a char buffer filled by a C function and converting it to a string. Here is the implementation of these including unittests that you can just drop into the string.d file if you remove the import line. I would very much like to see this included in phobos - no copyright/whatever needed.




// Remove when integrating into std.string.
import std.range, std.string, std.traits, std.utf;

/++
    Strips leading characters.
  +/
S stripLeft(S)(S s, S charsToStrip) pure
    if(isSomeString!S)
{
    bool foundIt;
    size_t notInSet;
    foreach(i, dchar c; s)
    {
        // Because of the call to indexOf, this function can't be @safe anymore.
        if(indexOf(charsToStrip, c) == -1)
        {
            foundIt = true;
            notInSet = i;
            break;
        }
    }

    if(foundIt)
        return s[notInSet .. $];

    return s[0 .. 0]; //Empty string with correct type.
}

unittest {
    debug(string) printf("string.stripLeft2.unittest\n");

    string hi = "Hello, world!";
    assert(hi.stripLeft("") == hi);
    assert(hi.stripLeft("H") == "ello, world!");
    assert(hi.stripLeft("Hel") == "o, world!");
    assert(hi.stripLeft("def") == hi);
    assert(hi.stripLeft(hi) == "");
}

/++
    Strips trailing characters.
  +/
S stripRight(S)(S s, S charsToStrip)
    if(isSomeString!S)
{
    alias typeof(s[0]) C;
    size_t codeLen;
    foreach(dchar c; retro(s))
    {
        // Because of the call to indexOf, this function can't be @safe anymore.
        if(indexOf(charsToStrip, c) >= 0)
            codeLen += codeLength!C(c);
        else
            break;
    }

    return s[0 .. $ - codeLen];
}

unittest {
    debug(string) printf("string.stripRight2.unittest\n");

    string hi = "Hello, worldd!";
    assert(hi.stripRight("") == hi);
    assert(hi.stripRight("!") == "Hello, worldd");
    assert(hi.stripRight("!.d") == "Hello, worl");
    assert(hi.stripRight("hex") == hi);
    assert(hi.stripRight(hi) == "");
}

/++
    Strips both leading and trailing characters.
  +/
S strip(S)(S s, S charsToStrip)
    if(isSomeString!S)
{
    return stripRight(stripLeft(s, charsToStrip), charsToStrip);
}

unittest {
    debug(string) printf("string.strip2.unittest\n");

    string hi = " ohfoo";
    assert(hi.strip("") == hi);
    assert(hi.strip(" ") == "ohfoo");
    assert(hi.strip(" o") == "hf");
    assert(hi.strip("ext") == hi);
    assert(hi.strip(" ohf") == "");
}