Although there are other data structures involved in the inner workings of a compiler, the AST performs a unique function. During the first stage, the syntax analysis stage, a compiler produces a parse tree. This parse tree can be used to perform almost all functions of a compiler by means of syntax-directed translation. Although this method can lead to a more efficient compiler, it goes against the software engineering principles of writing and maintaining programs. Another advantage that the AST has over a parse tree is the size, particularly the smaller height of the AST and the smaller number of elements.