US Patent 7823144 Computer program code comparison using lexemes

A method, apparatus and computer program product for comparing two computer program codes is disclosed. For each code, a stream of lexemes is generated for the program text of each code. The streams are concatenated in the same order as the program text. The two concatenated streams of lexemes are compared on a language-type by language-type basis to identify lexemes present only in one stream. The comparison derives a set of edit operations including minimal text block moves needed to convert one program code into the other program code.