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RETURN in BLOCK and PROG
- To: common-lisp at SU-AI
- Subject: RETURN in BLOCK and PROG
- From: Alan Bawden <ALAN at MIT-MC>
- Date: Mon, 20 Sep 1982 05:46:00 -0000
Date: Monday, 20 September 1982 01:14-EDT
For example, saying that RETURN is supposed to ignore named blocks
would force a choice between two unpleasant alternatives:
1) named PROG makes two blocks, a named one and an unnamed, which
makes it unanalogous to BLOCK, or
2) many uses of RETURN must be changed.
Alternative 1) is what I had in mind when I made the proposal. The idea is to
flush the misfeature of LispMachine Lisp where you cannot write a macro that
intoduces a block named FOO without also introducing a block named NIL which
then keeps the user from using RETURN inside the macro's body. Thus I regard
it as a win that named PROG and BLOCK will not be analogous.
This doesn't shaft the LispMachine users in the littlest bit since named PROG
and named DO continue to function in exactly the same way as they always have.