Hi Jonathan,
> (if 'any1 any2 . prg) -> any
> ...
> I also don't get the "." between "any2" and "prg" - does that mean
> something?
Yes. As you probably know, the dot is used in "dotted pairs" in Lisp, as
a result of a "cons" operation. In general, a list can be written
recursively as
(any . lst)
e.g.
: (1 . (2 3 4))
-> (1 2 3 4)
A 'prg' is a list of 'exe's (executable expressions). So a call like
(if (someCondition)
(doThat)
(doElse1)
(doElse2) )
can be dissected into
any1 (someCondition)
any2 (doThat)
prg ((doElse1) (doElse2))
: '(if (someCondition) (doThat) . ((doElse1) (doElse2)))
-> (if (someCondition) (doThat) (doElse1) (doElse2))
> Is there any significance in the difference of "any2" and "prg". I would
> have thought they were both "any" type parameters.
In some sense, yes. 'any' is the most general type, it can be anything,
i.e. a number, a symbol or a list. 'prg', however, is typically a list,
so it better describes what 'if' expects.
♪♫ Alex
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