Loop that collects results?

[kinghajj]

Is there a loop that returns a list of the results of each iteration? For example:

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(collect (n (sequence 1 10))
    (* n 2))
; => (2 4 6 8 10 12 14 16 18 20)

I'm sure there are other ways to do this, like using map and curry. I could probably implement this as a macro, if there is no current way to do this.

[cormullion]

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(map (fn (n) (* n 2)) (sequence 1 10))
;-> (2 4 6 8 10 12 14 16 18 20)

map will collect it for you.

[Jeff]

(map (curry * 2) '(1 2 3...))

[cormullion]

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(map << (sequence 1 10))

;-)

[Jeff]

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int main
{
    int seq[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    int result[10];
    int i;
    for (i = 0; i < 10; i++)
    {
        result[i] = seq[i] * 2;
    }
    return 0;
}

[/code]

[jrh]

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int main
{
    int seq[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    int result[10];
    int i;
    for (i = 0; i < 10; i++)
    {
        result[i] = seq[i] * 2;
    }
    return 0;
}

I think I see what you mean!

---

[jrh]

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> (rest (filter (lambda (x) (= (% x 2)0)) (sort (unique (rand 21 210)))))

(2 4 6 8 10 12 14 16 18 20)

---

[cormullion]

that's so silly, i love it!

[jrh]

Don't let that computer just sit there. Generate some cpu cycles!

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> (map eval (transpose (append (transpose (dup (list (sym (char 42)) 2) 10)) (list (rest (index string? (explode "C++  sucks!")))))))

(2 4 6 8 10 12 14 16 18 20)

---

[Jeff]

double_elements.so:

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void double_list_elements(int seq[], int seq_length, int result[])
{
    int i;
    for (i = 0; i < seq_length; i++)
    {
        result[i] = seq[i] * 2;
    }

}

my_script.lsp

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(import "double_elements.so "double_list_elements")
(set 'seq (sequence 1 10))
(set 'set2 '(array 10 (sequence 1 10))
(double_list_elements seq (length seq) seq2))