March 2014 update

Task/Knuths-algorithm-S/D/knuths-algorithm-s-1.d

@@ -8,7 +8,7 @@ auto sofN_creator(in int n) {
         i++;
         if (i <= n)
             sample ~= item;
-        else if (uniform(0.0, 1.0) < (cast(double)n / i))
+        else if (uniform(0.0, 1.0) < (double(n) / i))
             sample[uniform(0, n)] = item;
         return sample;
     };
@@ -18,12 +18,12 @@ void main() {
     enum nRuns = 100_000;
     size_t[10] bin;
 
-    foreach (trial; 0 .. nRuns) {
-        auto sofn = sofN_creator(3);
+    foreach (immutable trial; 0 .. nRuns) {
+        immutable sofn = sofN_creator(3);
         int[] sample;
-        foreach (item; 0 .. bin.length)
+        foreach (immutable item; 0 .. bin.length)
             sample = sofn(item);
-        foreach (s; sample)
+        foreach (immutable s; sample)
             bin[s]++;
     }
     writefln("Item counts for %d runs:\n%s", nRuns, bin);

Task/Knuths-algorithm-S/D/knuths-algorithm-s-2.d

@@ -1,7 +1,7 @@
 import std.stdio, std.random, std.algorithm;
 
 double random01(ref Xorshift rng) {
-    immutable r = rng.front / cast(double)rng.max;
+    immutable r = rng.front / double(rng.max);
     rng.popFront;
     return r;
 }
@@ -14,7 +14,7 @@ struct SOfN(size_t n) {
         i++;
         if (i <= n)
             sample[i - 1] = item;
-        else if (rng.random01 < (cast(double)n / i))
+        else if (rng.random01 < (double(n) / i))
             sample[uniform(0, n, rng)] = item;
         return sample[0 .. min(i, $)];
     }

Task/Knuths-algorithm-S/Objective-C/knuths-algorithm-s.m

@@ -3,33 +3,32 @@
 typedef NSArray *(^SOfN)(id);
 
 SOfN s_of_n_creator(int n) {
-  NSMutableArray *sample = [NSMutableArray arrayWithCapacity:n];
+  NSMutableArray *sample = [[NSMutableArray alloc] initWithCapacity:n];
   __block int i = 0;
-  return [[^(id item) {
+  return [^(id item) {
     i++;
     if (i <= n) {
       [sample addObject:item];
     } else if (rand() % i < n) {
-      [sample replaceObjectAtIndex:rand() % n withObject:item];
+      sample[rand() % n] = item;
     }
     return sample;
-  } copy] autorelease];
+  } copy];
 }
 
 int main(int argc, const char *argv[]) {
-  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
+  @autoreleasepool {
+
+    NSCountedSet *bin = [[NSCountedSet alloc] init];
+    for (int trial = 0; trial < 100000; trial++) {
+      SOfN s_of_n = s_of_n_creator(3);
+      NSArray *sample;
+      for (int i = 0; i < 10; i++)
+        sample = s_of_n(@(i));
+      [bin addObjectsFromArray:sample];
+    }
+    NSLog(@"%@", bin);
 
-  NSCountedSet *bin = [[NSCountedSet alloc] init];
-  for (int trial = 0; trial < 100000; trial++) {
-    SOfN s_of_n = s_of_n_creator(3);
-    NSArray *sample;
-    for (int i = 0; i < 10; i++)
-      sample = s_of_n([NSNumber numberWithInt:i]);
-    [bin addObjectsFromArray:sample];
   }
-  NSLog(@"%@", bin);
-  [bin release];
-
-  [pool release];
   return 0;
 }

Task/Knuths-algorithm-S/Racket/knuths-algorithm-s.rkt

@@ -1,29 +1,29 @@
-#lang racket
+#lang racket/base
 
 (define (s-of-n-creator n)
-  (let* ([count 0] ; 'i' in the description
+  (let ([count 0] ; 'i' in the description
          [vec (make-vector n)]) ; store the elts we've seen so far
     (lambda (item)
       (if (< count n)
           ; we're not full, so, kind of boring
           (begin
             (vector-set! vec count item)
-            (set! count (+ count 1))
-            (vector-copy vec 0 count))
+            (set! count (+ count 1)))
           ; we've already seen n elts; fun starts
           (begin
             (set! count (+ count 1))
-            (when (< (random) (/ n count))
-              (vector-set! vec (random n) item))
-            (vector-copy vec))))))
+            (when (< (random count) n)
+              (vector-set! vec (random n) item))))
+      vec)))
+
+(define counts (make-vector 10))
 
-(define counts (make-hash '((0 . 0) (1 . 0) (2 . 0) (3 . 0) (4 . 0) (5 . 0) (6 . 0) (7 . 0) (8 . 0) (9 . 0))))
 (for ([iter (in-range 0 100000)]) ; trials
   (let ([s-of-n (s-of-n-creator 3)]) ; set up the chooser
     (for ([d (in-vector ; iterate over the chosen digits
               (for/last ([digit (in-range 0 10)]) ; loop through the digits
                         (s-of-n digit)))]) ; feed them in
-      (hash-update! counts d add1)))) ; update counts
+      (vector-set! counts d (add1 (vector-ref counts d)))))) ; update counts
 
 (for ([d (in-range 0 10)])
-  (printf "~a ~a~n" d (hash-ref counts d)))
+  (printf "~a ~a~n" d (vector-ref counts d)))