[Issue 7146] New: enhance strip* (implementation provided)

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=7146

           Summary: enhance strip* (implementation provided)
           Product: D
           Version: D2
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: pompei2 at gmail.com


--- Comment #0 from pompei2 at gmail.com 2011-12-21 00:50:17 PST ---
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") == "");
}

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