OneArmedIf + EmptyDefine

[jcubic]

It seems this is missing. In Guile and Chicken.

(define x)
(eq? (if #f #f) x)
#t

so define without value may be another way to define unspecified value.
So those two surveys can be somehow connected or linked.

[lassik]

Indeed. We could merge these surveys (and maybe more) into one survey about what happens when different expressions (if, cond, define, begin, ...) have a missing body.

[lassik]

In some implementations, an empty (begin) returns a different value depending on the situation. (Gauche used to return the last value in a VM register.)

[lassik]

Some expressions to try:

(define foo)
(define (foo))
(begin)
(cond)
(cond (else))
(if #f 2)
(guard (e (else)) (error "foo"))