+
+void normalise(double v[D3], double one, double absepsilon) {
+ int k;
+ double multby= one/(magnD(v) + absepsilon);
+ K v[k] *= multby;
+}
+
+void xprod_norm(double r[D3], const double a[D3], const double b[D3],
+ double one, double absepsilon) {
+ xprod(r,a,b);
+ normalise(r, absepsilon, one);
+}
+
+double dotprod(const double a[D3], const double b[D3]) {
+ int k;
+ double result= 0;
+ K result += a[k] * b[k];
+ return result;
+}
+
+void libdie(const char *lib, int l, const char *str) {
+ fprintf(stderr,"%s library call failed, line %d: %s\n", lib, l, str);
+}
+
+void gsldie(int l, const char *what, int status) {
+ fprintf(stderr,"gsl function failed, line %d: %s: %s\n",
+ l, what, gsl_strerror(status));
+ exit(-1);
+}
+
+void diee(const char *what) { perror(what); exit(16); }
+void fail(const char *emsg) { fputs(emsg,stderr); exit(12); }
+void flushoutput(void) { if (ferror(stdout)||fflush(stdout)) diee("stdout"); }