Out of interest, is this just about _passing_ a string, or that a string is involved (since in the latter case, there seems little avoiding that in nearly every part of the code base). In a practical sense, that's a hold-over from an earlier version of the code -- in that code I was considering ways of making the shared handling more generally applicable than for just min and max, though since I retired that idea, there's no reason not to retire the string passing.