The idea is to add partial applications without expanding the type size. It is done by adding a new instruction, "PARTIAL", standing for "Partial application".
Upon encountering this instruction on a stack containing the capture (of type capture_ty) and a lambda (of type
(capture_ty , arg_ty) -> ret_ty), a
PUSH capture_ty capture ; PAIR is prepended to the lambda, yielding a lambda of type
arg_ty -> ret_ty.
Tests have yet to be written.