Semantic Analyzer Needed for an already-built Parser in a compiler

I currently have a parser that works in collaboration with a scanner to verify a submitted program is valid or not. I now need someone to build a semantic analyzer for the parser. This will be done in C or C++. I have all the requirements. The grammar is very elementary and is less than 20 lines long. I would like the output of the program to be a traversal of the decorated parse tree.