In the previous article I put a small indicator under the MetaEditor profiler and let two columns of numbers tell me where its time was going. The profiler answers one question well: where is this program slow? It has nothing to say about a different and often costlier question, the one where the program is fast enough but simply wrong. A line draws smoothly, the terminal reports no error, and yet the values it plots are quietly incorrect. For that class of problem MetaEditor ships a separate ...