Dear Cafe, I use `buildExpressionParser` https://hackage.haskell.org/package/parsec-3.1.14.0/docs/Text-Parsec-Expr.ht... with a table similar to https://hackage.haskell.org/package/haskell-src-exts-1.23.0/docs/Language-Ha... and I find it's somewhat expensive. I think the algorithm makes me pay for each operator that is in the table even when just a few of them are actually in the input. (I removed from the table those that don't appear in my test cases, and it got faster.) Certainly this is known? What could be done about it? What does Megaparsec do? It seems that Text.Megaparsec.Expr vanished from version 6 to version 7. A classical shift/reduce algorithm would help (?) but not with the given type of table, which does not allow to parse an operator just once, and then look up its precedence. - J.W.