Hello, does some plans for an library for expression evaluation exist? The user should be able to define its own operators (unary and binary with priority/affinity) and operands. The user can then store a sequence of its operators and operands in a vector in infix order. A special function creates from the vector an expression tree and evaluates the tree (calling the implemented action of each operator/operand -> the action can depend of the subsequent/child operators). With regards, Oliver