- SECD: about
- Part I and Part Ia describe high-level, formal definition of a SECD machine;
- Part II discusses low-level details of SECD C implementation;
- Part III (TODO): how to compile a Scheme subset into SECD code.
Things are getting dirty: putting functional in the SECD
Now we’re starting the most interesting part, adding functions into the functional virtual machine. First of all, a function is usually tied to its environment: a pair of function definition (arguments and body) and the environment it has been created in is called closure. So don’t be afraid of this semantic rules for opcode
LDF (the newly made closure is underlined):
(s, e, LDF.(args body).c, d) => (((args body).e).s, e, c, d)
I want to stress that the environment is paired with the function definition on the stack, producing a closure
(args body).e, which may be saved, used as an argument to another function (thus bound to a symbol), and so on.
The closure on top of the stack may be called using opcode
(((argnames body).e').argvals.s, e, AP.c, d)
=> ( (), new-frame(argnames, argvals).e', body, s.e.c.d)