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otccex.c
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otccex.c
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/* #!/usr/local/bin/otcc */
/*
* Sample OTCC C example. You can uncomment the first line and install
* otcc in /usr/local/bin to make otcc scripts !
*/
/* Any preprocessor directive except #define are ignored. We put this
include so that a standard C compiler can compile this code too. */
#include <stdio.h>
/* defines are handled, but macro arguments cannot be given. No
recursive defines are tolerated */
#define DEFAULT_BASE 10
/* global variables can be used */
int base;
/*
* Only old style K&R prototypes are parsed. Only int arguments are
* allowed (implicit types).
*
* By benchmarking the execution time of this function (for example
* for fib(35)), you'll notice that OTCC is quite fast because it
* generates native i386 machine code.
*/
fib(n)
{
if (n <= 2)
return 1;
else
return fib(n-1) + fib(n-2);
}
/* Identifiers are parsed the same way as C: begins with letter or
'_', and then letters, '_' or digits */
fact(n)
{
/* local variables can be declared. Only 'int' type is supported */
int i, r;
r = 1;
/* 'while' and 'for' loops are supported */
for(i=2;i<=n;i++)
r = r * i;
return r;
}
/* Well, we could use printf, but it would be too easy */
print_num(n, b)
{
int tab, p, c;
/* Numbers can be entered in decimal, hexadecimal ('0x' prefix) and
octal ('0' prefix) */
/* more complex programs use malloc */
tab = malloc(0x100);
p = tab;
while (1) {
c = n % b;
/* Character constants can be used */
if (c >= 10)
c = c + 'a' - 10;
else
c = c + '0';
*(char *)p = c;
p++;
n = n / b;
/* 'break' is supported */
if (n == 0)
break;
}
while (p != tab) {
p--;
printf("%c", *(char *)p);
}
free(tab);
}
/* 'main' takes standard 'argc' and 'argv' parameters */
main(argc, argv)
{
/* no local name space is supported, but local variables ARE
supported. As long as you do not use a globally defined
variable name as local variable (which is a bad habbit), you
won't have any problem */
int s, n, f;
/* && and || operator have the same semantics as C (left to right
evaluation and early exit) */
if (argc != 2 && argc != 3) {
/* '*' operator is supported with explicit casting to 'int *',
'char *' or 'int (*)()' (function pointer). Of course, 'int'
are supposed to be used as pointers too. */
s = *(int *)argv;
help(s);
return 1;
}
/* Any libc function can be used because OTCC uses dynamic linking */
n = atoi(*(int *)(argv + 4));
base = DEFAULT_BASE;
if (argc >= 3) {
base = atoi(*(int *)(argv + 8));
if (base < 2 || base > 36) {
/* external variables can be used too (here: 'stderr') */
fprintf(stderr, "Invalid base\n");
return 1;
}
}
printf("fib(%d) = ", n);
print_num(fib(n), base);
printf("\n");
printf("fact(%d) = ", n);
if (n > 12) {
printf("Overflow");
} else {
/* why not using a function pointer ? */
f = &fact;
print_num((*(int (*)())f)(n), base);
}
printf("\n");
return 0;
}
/* functions can be used before being defined */
help(name)
{
printf("usage: %s n [base]\n", name);
printf("Compute fib(n) and fact(n) and output the result in base 'base'\n");
}