On Wednesday, April 2, 2014 3:39:47 PM UTC-5, Christopher Howard wrote: > > On Wed, 2 Apr 2014 14:07:47 -0600 > Timothy Baldridge <tbald...@gmail.com <javascript:>> wrote: > > > I don't know of anything built-in, but this should do the trick: > > > > (defn remove-first [f [head & tail]] > > (if (f head) > > tail > > (cons head (lazy-seq (remove-first f tail))))) > > > > Timothy > > > > > > Thanks. This seems to work for my purposes, although I modified it to > handle the empty vector: > > (defn remove-first [f [head & tail]] > (if (not head) [] > (if (f head) > tail > (cons head (lazy-seq (remove-first f tail)))))) > > This implementation doesn't seem to work on everything that "remove" > works on: > > com.example.myapp=> (remove #(= [1 2] %) {1 2 3 4}) > ([3 4]) > com.example.myapp=> (remove-first #(= [1 2] %) {1 2 3 4}) > UnsupportedOperationException nth not supported on this type: > PersistentArrayMap clojure.lang.RT.nthFrom (RT.java:835) > To fix that, use `seq` on the collection argument. Also, if you want a emtpy sequence as a result instead of nil, just move the lazy-seq up since (lazy-seq nil) is an empty sequence. (lazy-seq (when-let [[head & tail] (seq coll)] ...)
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