Internal structure

The compiler works in several passes, which may be broadly grouped as

• syntactic analysis: source inclusion, lexical analysis, parsing, macro expansion,

• semantic analysis: scope binding, type inference,

• intermediate Foam code generation,

• intermediate code optimization (several individual passes),

• concrete code generation: to C or Lisp.

The compiler can generate or accept files between any of these groups. For example, when machine-generating programs it is possible to bypass the syntax analysis and pass generated abstract syntax trees into the semantic analysis phase.

The compiler is about 120,000 lines of C code and 6000 lines of code in its current implementation. About 1% of the compiler is code for Lisp generation and about 3% is code for C generation. Some code is shared between the general library and the default run time system. Most of the run-time system is written in , with the rest written in C or Lisp depending on the platform.