carp-lang/Carp
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Merge pull request #622 from hellerve/cxr

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macros: add cxr, nthcar, and nthcdr
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Erik Svedäng 2019-11-25 12:58:24 +01:00 committed by GitHub
commit e850da236f
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1 changed files with 19 additions and 0 deletions
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core/Macros.carp
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@ -73,6 +73,25 @@
(defndynamic cdddar [pair] (cdr (cdr (cdr (car pair)))))
(defndynamic cddddr [pair] (cdr (cdr (cdr (cdr pair)))))
(defndynamic cxr [x pair]
(if (= (length x) 0)
(list 'quote pair)
(list
(if (= 'a (cadr x))
'car
(if (= 'd (cadr x))
'cdr
(macro-error "`cxr` expects either `a` or `d` symbols, got " (cadr x))))
(if (= 1 (car x))
(cxr (cddr x) pair)
(cxr (cons (- (car x) 1) (cdr x)) pair)))))
(defndynamic nthcdr [n pair]
(cxr (list n 'd) pair))
(defndynamic nthcar [n pair]
(cxr (list 1 'a n 'd) pair))
(defndynamic eval-internal [form]
(list 'do
(list 'defn 'main [] (list 'IO.println* form))