-- | Basic function to extend a given signature by adding an item (id) to it
addToSig :: Sign -> Token -> OpType -> Sign
addToSig sig tok ot = sig {items = Map.insert tok ot $ items sig}
addToSig :: Sign -> Token -> OpType -> Sign
addToSig sig tok ot = sig {items = Map.insert tok ot $ items sig}
addToSig sig tok ot = sig {items = Map.insert tok ot $ items sig}