https://github.com/akkartik/mu/blob/master/067random.cc
 1 :(before "End Primitive Recipe Declarations")
 2 REAL_RANDOM,
 3 :(before "End Primitive Recipe Numbers")
 4 put(Recipe_ordinal, "real-random", REAL_RANDOM);
 5 :(before "End Primitive Recipe Checks")
 6 case REAL_RANDOM: {
 7   break;
 8 }
 9 :(before "End Primitive Recipe Implementations")
10 case REAL_RANDOM: {
11   // todo: limited range of numbers, might be imperfectly random
12   // todo: thread state in extra ingredients and products
13   products.resize(1);
14   products.at(0).push_back(rand());
15   break;
16 }
17 
18 :(before "End Primitive Recipe Declarations")
19 MAKE_RANDOM_NONDETERMINISTIC,
20 :(before "End Primitive Recipe Numbers")
21 put(Recipe_ordinal, "make-random-nondeterministic", MAKE_RANDOM_NONDETERMINISTIC);
22 :(before "End Primitive Recipe Checks")
23 case MAKE_RANDOM_NONDETERMINISTIC: {
24   break;
25 }
26 :(before "End Primitive Recipe Implementations")
27 case MAKE_RANDOM_NONDETERMINISTIC: {
28   srand(time(NULL));
29   break;
30 }
31 
32 // undo non-determinism in later tests
33 :(before "End Reset")
34 srand(0);