Yes, if-and-let is similar to if-let-all. On Friday, June 5, 2015 at 10:47:24 PM UTC+9, Fluid Dynamics wrote: > > On Friday, June 5, 2015 at 1:53:07 AM UTC-4, crocket wrote: >> >> Ouch, I didn't write. Gary Fredericks wrote it. I simply modified his >> if-let-all macro a little bit. >> >> On Friday, June 5, 2015 at 2:44:22 PM UTC+9, crocket wrote: >>> >>> 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. >>> >>> > Didn't I post something with a similar purpose a while back, called > "if-and-let"? That one had some trickiness to avoid unexpectedly shadowing > things unpredictably in false-case, as I recall. >
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