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#other-lisps
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2020-02-12
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Eric Ihli16:02:17

I'm trying to learn Common Lisp and I'm stuck on something.

(map 'list '+ (mapcar
                (lambda (s)
                 (sums-of-children ht s))
                children))
That doesn't work because the syntax needs to be (map <type> <fn> a b c rest...) and I'm giving it (map <type> <fn> (list of a b c rest...) I can't figure out how to re-write it in a way that works. I'm experimenting with backquoting and using unquote-splice, but that seems way too contrived to be correct.

Eric Ihli16:02:47

For context, this is inside a recursive function, sums-of-children , which returns a list of (<int> <int>) if it's a leaf and the sum of it's children (`(<sum of children car> <sum of children cadr)`) if it's not a leaf.

Eric Ihli16:02:56

Ah hah. A misunderstanding of apply. Simple. Just put apply at the beginning of that first form I'm using. https://stackoverflow.com/questions/2627262/how-do-i-splice-into-a-list-outside-of-a-macro-in-common-lisp