Separate compilation

[Steven Pemberton]

In article <5918 at lanl.ARPA> crs at lanl.UUCP writes:
> (I realize that the lack of "separate compilation" in Pascal
> precludes use of precompiled libraries of functions.)

This question arises every now and then. But, there is nothing about Pascal
that precludes separate compilation: just because some implementations
demand extra syntax to handle it does not mean that that extra syntax is
necessary.

I have used a compiler (for Algol 68 as it happens but the idea is the same)
that handled separate compilation without external declarations, includes or
the like. It worked as follows (translated into Unix-like terms):

Your separately compiled procedures looked like this: (it also allowed
separately compiled constants, types and variables)

	program whatever(...etc...);

	function mysqrt(x: real): real;
	begin ...etc... end;

	function mysin(x: real): real;
	begin ...etc... end;

	begin (*Empty main program, though it didn't have to be: you could
		initialise variables here*)
	end.

You then compiled this with the equivalent of pc -c mylib.p, and this
produced mylib.a.

Your program then looked like this:

	program p(...etc...);
	(*more procedures if you want*)
	begin
		writeln(mysqrt(4.0))
	end.

and you compiled this with pc mylib.a prog.p. The compiler picked up all
type information from the .a file, and so strong typing was still done.

It always struck me as a well thought out method.

Steven Pemberton, CWI, Amsterdam; steven at mcvax.uucp