Hi folks! I have the following problem. As code is most time easier to understand, let give an example what I try to do in C: unsigned int i,j; unsigned int r[100]; for (i = 0; i < 1000000; i++) { j = makeResult(); //j is known to be smaller than 100. r[j] = r[j] + 1; } (My C is poor, so please don't laugh) Currently I'm using a Data.Map for this, but as the result is bounded in this area, an array seems to be more appropreate. I don't want to mess with mutable arrays, but I can't find anything which does the same like Data.Map.insertWith for arrays in a reasonable way. In my example, the input comes from a lazy list and is than folded into the Map by insertWith (+) j 1 r. Is there any nice, quick way to do this with Arrays without using mutable ones? Yours, Robert Clausecker