examples/higher.spl

   1 map(f, l){
   2         if(isEmpty(l)){
   3                 return [];
   4         } else {
   5                 return f(l.hd) : map(f, l.tl);
   6         }
   7 }
   8
   9 foldr(f, acc, l){
  10         if(isEmpty(l)){
  11                 return acc;
  12         } else {
  13                 return foldr(f, f(acc, l.hd), l.tl);
  14         }
  15 }
  16
  17 filter(f, l){
  18         if(isEmpty(l)){
  19                 return [];
  20         } else {
  21                 if(f(l.hd)){
  22                         return filter(f, l.tl);
  23                 } else {
  24                         return l.hd : filter(f, l.tl);
  25                 }
  26         }
  27 }
  28
  29 intList(x){
  30         if(x <= 1){
  31                 return [x];
  32         } else {
  33                 return x : intList(x-1);
  34         }
  35 }
  36
  37 giveF(){
  38     return (\x->x+1);
  39 }
  40
  41 plus(x, y){
  42     return x + y;
  43 }
  44
  45 ap(f, x) { return f(x); }
  46
  47 mapF(f, xs) {
  48     if(isEmpty(xs)) {
  49         return [];
  50     } else {
  51         return (ap(f, xs.hd)) : mapF(f, xs.tl);
  52     }
  53 }
  54
  55 main(){
  56     var x = 5;
  57
  58     var f = giveF();
  59
  60     var plus = \x y->x+y;
  61
  62     var g = map(plus, [1,2,3]);
  63     var is = mapF(\f->f(1), g);
  64     //var is = map(\f->f(1), g);
  65     var p = g.hd;
  66     var q = p(1);
  67
  68     //print("is.hd", is.hd);
  69
  70     print("f(4) = ", f(4));
  71
  72         print("faculty of 5 is: ", foldr(\x y->x*y, 1, intList(5)));
  73         print("sum of 1..5 is: ", foldr(\x y->x+y, 0, intList(5)));
  74         print("sum of 0..12 but only the evens: ",
  75                 foldr(\x y->x+y, 0, filter(\x->x%2 == 0, intList(12))));
  76
  77
  78 }