On 2/21/15 4:57 AM, Cecil Westerhof wrote:
I want to work with default values. For this I use:
[& nr]
This gives the value null to nr. So far so good.
But I want to propagate the value, because I want to fill the default at a
higher level.
I have:
(defn test-lucky-numbers-all
"Test all lucky number performance"
[& nr]
(printf "all: %s\n\n" nr)
(time
(do (test-lucky-numbers-first nr)
and:
(defn test-lucky-numbers-first
"Performance test of lucky numbers (first)"
[& nr]
(printf "first: %s\n\n" nr)
>
When I do:
(test-lucky-numbers-all)
The first prints:
all: null
but the second prints:
first: (nil)
And when I do:
(test-lucky-numbers-all 1)
The first prints:
all: (1)
and the second prints:
first: ((1))
What is happening here and what can I do about it?
You can "unwrap" the varargs by destructuring them like so:
(defn foo [a b & [c d]]
(list a b (+ c d)))
(foo 1 2 3 4) ;; => (1 2 7)
This is possible because the varargs are provided as a seq.
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