Re: sorted-map-by sample call

[Stephen C. Gilardi]

On Jun 22, 2009, at 1:23 AM, kkw wrote:

   I had some fortune with the sorted-by function:

1:11 user=> (sort-by (fn [e] (second e)) [[1 99] [3 4] [5 6] [7 8]])
([3 4] [5 6] [7 8] [1 99])

You were using the form of sort-by that accepts a "keyfn", not the one where you also provide a comparator.

   so I thought I'd have a go with sorted-map-by also:

1:13 user=> (doc sorted-map-by)
-------------------------
clojure.core/sorted-map-by
([comparator & keyvals])
 keyval => key val
 Returns a new sorted map with supplied mappings, using the supplied
comparator.

1:14 user=> (sorted-map-by (fn [c] c) 1 2)
{1 2}

No comparisons were necessary, so your comparator function wasn't called.

1:16 user=> (sorted-map-by (fn [c] c) 1 2 3 4)
java.lang.RuntimeException: java.lang.IllegalArgumentException: Wrong
number of args passed to: user$eval--85$fn (repl-1:16)

--Steve

sorted-map-by called your comparator, but comparators take two arguments and your function only accepts one.

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