Jack Palevich | 21a15a2 | 2009-05-11 14:49:29 -0700 | [diff] [blame] | 1 | /* #!/usr/local/bin/otcc */ |
| 2 | /* |
| 3 | * Sample OTCC C example. You can uncomment the first line and install |
| 4 | * otcc in /usr/local/bin to make otcc scripts ! |
| 5 | */ |
| 6 | |
| 7 | /* Any preprocessor directive except #define are ignored. We put this |
| 8 | include so that a standard C compiler can compile this code too. */ |
| 9 | #include <stdio.h> |
| 10 | |
| 11 | /* defines are handled, but macro arguments cannot be given. No |
| 12 | recursive defines are tolerated */ |
| 13 | #define DEFAULT_BASE 10 |
| 14 | |
| 15 | /* |
| 16 | * Only old style K&R prototypes are parsed. Only int arguments are |
| 17 | * allowed (implicit types). |
| 18 | * |
| 19 | * By benchmarking the execution time of this function (for example |
| 20 | * for fib(35)), you'll notice that OTCC is quite fast because it |
| 21 | * generates native i386 machine code. |
| 22 | */ |
| 23 | fib(n) |
| 24 | { |
| 25 | if (n <= 2) |
| 26 | return 1; |
| 27 | else |
| 28 | return fib(n-1) + fib(n-2); |
| 29 | } |
| 30 | |
| 31 | /* Identifiers are parsed the same way as C: begins with letter or |
| 32 | '_', and then letters, '_' or digits */ |
| 33 | fact(n) |
| 34 | { |
| 35 | /* local variables can be declared. Only 'int' type is supported */ |
| 36 | int i, r; |
| 37 | r = 1; |
| 38 | /* 'while' and 'for' loops are supported */ |
| 39 | for(i=2;i<=n;i++) |
| 40 | r = r * i; |
| 41 | return r; |
| 42 | } |
| 43 | |
| 44 | /* Well, we could use printf, but it would be too easy */ |
| 45 | print_num(n, b) |
| 46 | { |
| 47 | int tab, p, c; |
| 48 | /* Numbers can be entered in decimal, hexadecimal ('0x' prefix) and |
| 49 | octal ('0' prefix) */ |
| 50 | /* more complex programs use malloc */ |
| 51 | tab = malloc(0x100); |
| 52 | p = tab; |
| 53 | while (1) { |
| 54 | c = n % b; |
| 55 | /* Character constants can be used */ |
| 56 | if (c >= 10) |
| 57 | c = c + 'a' - 10; |
| 58 | else |
| 59 | c = c + '0'; |
| 60 | *(char *)p = c; |
| 61 | p++; |
| 62 | n = n / b; |
| 63 | /* 'break' is supported */ |
| 64 | if (n == 0) |
| 65 | break; |
| 66 | } |
| 67 | while (p != tab) { |
| 68 | p--; |
| 69 | printf("%c", *(char *)p); |
| 70 | } |
| 71 | free(tab); |
| 72 | } |
| 73 | |
| 74 | /* 'main' takes standard 'argc' and 'argv' parameters */ |
| 75 | main(argc, argv) |
| 76 | { |
| 77 | /* no local name space is supported, but local variables ARE |
| 78 | supported. As long as you do not use a globally defined |
| 79 | variable name as local variable (which is a bad habbit), you |
| 80 | won't have any problem */ |
| 81 | int s, n, f, base; |
| 82 | |
| 83 | /* && and || operator have the same semantics as C (left to right |
| 84 | evaluation and early exit) */ |
| 85 | if (argc != 2 && argc != 3) { |
| 86 | /* '*' operator is supported with explicit casting to 'int *', |
| 87 | 'char *' or 'int (*)()' (function pointer). Of course, 'int' |
| 88 | are supposed to be used as pointers too. */ |
| 89 | s = *(int *)argv; |
| 90 | help(s); |
| 91 | return 1; |
| 92 | } |
| 93 | /* Any libc function can be used because OTCC uses dynamic linking */ |
| 94 | n = atoi(*(int *)(argv + 4)); |
| 95 | base = DEFAULT_BASE; |
| 96 | if (argc >= 3) { |
| 97 | base = atoi(*(int *)(argv + 8)); |
| 98 | if (base < 2 || base > 36) { |
| 99 | /* external variables can be used too (here: 'stderr') */ |
| 100 | fprintf(stderr, "Invalid base\n"); |
| 101 | return 1; |
| 102 | } |
| 103 | } |
| 104 | printf("fib(%d) = ", n); |
| 105 | print_num(fib(n), base); |
| 106 | printf("\n"); |
| 107 | |
| 108 | printf("fact(%d) = ", n); |
| 109 | if (n > 12) { |
| 110 | printf("Overflow"); |
| 111 | } else { |
| 112 | /* why not using a function pointer ? */ |
| 113 | f = &fact; |
| 114 | print_num((*(int (*)())f)(n), base); |
| 115 | } |
| 116 | printf("\n"); |
| 117 | return 0; |
| 118 | } |
| 119 | |
| 120 | /* functions can be used before being defined */ |
| 121 | help(name) |
| 122 | { |
| 123 | printf("usage: %s n [base]\n", name); |
| 124 | printf("Compute fib(n) and fact(n) and output the result in base 'base'\n"); |
| 125 | } |
| 126 | |