>>53357162
Did you ever consider that you're supposed to actually learn something (and/or apply shit you learned) from this task?

>>53357162
We're not going to do your homework for you faggot

main = putStrLn(arrow 9)

arrow n = unlines $
    [[star (x >= mid-1 && x <= mid+1) | x <- w]] ++
    [[star (x == mid-1 || x == mid+1) | x <- w] | y <- [2..mid]] ++
    [[star (x /= mid) | x <- w]] ++
    [[star (x == mid-y || x == mid+y) | x <- w] | y <- [mid-1,mid-2..0]]
  where mid = n `div` 2
        w   = [0..n-1]
        star True  = '*'
        star False = ' '

h-how did I do?

n/3 spaces, n/3 stars, n/3 spaces
n/3 * (n/3 spaces, 1 star, n/3-2 spaces, 1 star, n/3 spaces)
n3/+1 stars,n/3-2 spaces, n/3+1 stars
etc

File: 2016-03-07-142919_263x415_scrot.png (3 KB, 263x415) Image search: [Google]

3 KB, 263x415

>>53357342
Really nice, would be even cooler if the top part would scale too.
Here is my attempt for that:

main = putStrLn(arrow 23)

arrow :: Integer -> String
arrow n = unlines $
    [[star (x >= mid-o && x <= mid+o) | x <- w]] ++
    [[star (x == mid-o || x == mid+o) | x <- w] | y <- [2..mid]] ++
    [[star (x <= mid-o || x >= mid+o) | x <- w]] ++
    [[star (x == mid-y || x == mid+y) | x <- w] | y <- [mid-1,mid-2..0]]
  where mid = n `div` 2
        o   = floor $ (fromInteger n) / 5
        w   = [0..n-1]
        star True  = '*'
        star False = ' '

>>53359108
nice

>>53359108
>>53357342
>>53357596
thanks

>>53357291
no one made you

This faggot is gonna enter the workforce someday

Here you go, OP.

#include <stdlib.h>
#include <tcl.h>
#define MULTILINE(...) #__VA_ARGS__
/* Compile with
    cc arrow-tcl.c -o arrow-tcl -ltcl
*/

int main(int argc, char* argv[]) {
    Tcl_Interp *interp = Tcl_CreateInterp();
    if (Tcl_Init(interp) != TCL_OK) {
        return EXIT_FAILURE;
    }
    Tcl_Eval(interp, MULTILINE(
        package require Tcl 8.5;

        proc arrow n {
            set result {};
            set mid [expr {$n / 2}];
            set p1 [expr {$n / 3}];
            set p2 [expr {2 * $n / 3}];
            for {set i 0} {$i < $n} {incr i} {
                for {set j 0} {$j < $n} {incr j} {
                    set star? [expr {
                        ($i == 0 && $j >= $p1 && $j <= $p2) ||
                        ($i > 0 && $i < $mid && ($j == $p1 || $j == $p2)) ||
                        ($i == $mid && ($j <= $p1 || $j >= $p2)) ||
                        ($i > $mid && ($j == $i - $mid || $j == $n - $i + $mid - 1))
                    }];
                    append result [lindex {{ } *} ${star?}]
                };
                append result \\n;
            };
            return $result;
        };

        arrow [gets stdin];
    ));
    printf("%s", Tcl_GetStringResult(interp));
    Tcl_Finalize();
    return EXIT_SUCCESS;
    return 0;
}

>>53359108
Just noticed that

o = n `div` 5

would be shorter. I was just trying out stuff and didn't clean it up properly.

>>53359707
If you only need multiples of three it will look better with

set p2 [expr {2 * $n / 3 - 1}];

>>53359411
>no one made you
That's not how it works, faggot.

>>53357162
It's really shitty, lots of variable overlap, but got tired of working on ur stupid homework.

#lang racket

(provide (all-defined-out))

(define (divisible-by-3? n)
  (and (exact-positive-integer? n) (zero? (modulo n 3))))

(define/contract (arrow-line size)
  (divisible-by-3? . -> . string?)
  (define segment (ceiling (/ size 3)))
  (define leading (make-string segment #\space))
  (define inner (if (>= size 9) (make-string (ceiling (/ segment 3)) #\space) ""))
  (define (make-line x)
    (string-append leading (if (zero? x)
                               (make-string segment #\*)
                               (string-append "*" inner "*"))))
  (match size
    [3 " *"]
    [_ (string-join (map make-line (range (floor (/ size 2)))) "\n")]))

(define/contract (arrow-triangle size)
  (divisible-by-3? . -> . string?)
  (define len (ceiling (/ size 2)))
  (define inner (if (>= size 9) (make-string (ceiling (/ size 3 3)) #\space) ""))
  (define wing (make-string (ceiling (- (/ size 2) (/ size 3 3))) #\*))
  (define (make-line x)
    (define s (- size (+ (* x 2) 2)))
    (string-append (make-string x #\space)
                   (cond
                     [(zero? x)  (if (= size 3) "***" (string-append wing inner wing))]
                     [(<= s 0) (if (even? size) "**" "*")]
                     [else (string-append "*" (make-string s #\space) "*")])))
  (string-join (map make-line (range len)) "\n"))

(define/contract (arrow size)
  (divisible-by-3? . -> . string?)
  (string-append (arrow-line size)
                 "\n"
                 (arrow-triangle size)))

(module+ main
  (for ([size '(3 6 9 12)])
    (printf "Size ~a\n\n~a\n\n" size (arrow size))))

I won't try and solve it right now, but I'll tell you that usually the easiest way to solve problems like these (printing symmetrical patterns of characters) is using the backspace escape character. I might have a look at this later.

>>53357162
nice arrow xD upvoted :P