The macro below is called if-let-all.
(defmacro if-let-all
"if-let-all evaluates every local binding sequentially and evaluates
true-case only if every local binding is a truthy value.
true-case has access to all local bindings, but false-case doesn't have access
to local bindings."
[bindings true-case false-case]
(let [pairs (partition 2 bindings)
names (mapv first pairs)
exprs (map second pairs)
exprs-in-if-let (fn self [[name1 & more-names] [expr1 & more-exprs]]
`(if-let [~name1 ~expr1]
~(if more-names
(self more-names more-exprs)
names)))
things (exprs-in-if-let names exprs)]
`(if-let [~names ~things]
~true-case
~false-case)))
You can use it as (if-let-all [a 2 b 3] (+ a b) "oh no!!"). false-case doesn't
have access to local bindings.
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