+unsigned pa_gcd(unsigned a, unsigned b);
+void pa_reduce(unsigned *num, unsigned *den);
+
+unsigned pa_ncpus(void);
+
+char *pa_replace(const char*s, const char*a, const char *b);
+
+char *pa_unescape(char *p);
+
+char *pa_realpath(const char *path);
+