The interpreting availability in libx1f4i0 comes in layers. The lowest layer is the expression evaluation and is provided by the previously described expression evaluator. The second layer adds control statements and allows for variable declaration. It makes use of the expression evaluation capability of the lower layer. It thus makes up for an imperative programming language interpreter. The third layer adds functions. The very bodies of the interpreted functions are treated as function-less programs and their interpretation is defaulted to the mid second layer. Call this third procedural programming language interpreter.
The AEPL interpreters build upon and extend the expression evaluator. Such, most that apply for the expression evaluator, both in terms of evaluated syntax and programming interface do apply for the AEPL interpreters as well.
Some of the (via programming languages) application extending common places are visited in this chapter.