View Compilation Error

0_0_9069934_31073.c:12: error: syntax error before "is_num"
0_0_9069934_31073.c: In function `is_num':
0_0_9069934_31073.c:15: error: `true' undeclared (first use in this function)
0_0_9069934_31073.c:15: error: (Each undeclared identifier is reported only once
0_0_9069934_31073.c:15: error: for each function it appears in.)
0_0_9069934_31073.c:17: error: `false' undeclared (first use in this function)