Use enumerations where appropriate

Enumerations have the following advantages over #define:
- they clearly connect a variable and the allowed constants,
- the meaning of code is not obfuscated by integer values,
- they are visible to the compiler, which can warn about (possibly)
  incorrect usage.

There should be no functional change.

1 files changed, 8 insertions, 5 deletions

diff --git a/src/PJ_stere.c b/src/PJ_stere.c
index 02b73507..500b512d 100644
--- a/src/PJ_stere.c
+++ b/src/PJ_stere.c
@@ -7,12 +7,19 @@ PROJ_HEAD(stere, "Stereographic") "\n\tAzi, Sph&Ell\n\tlat_ts=";
 PROJ_HEAD(ups, "Universal Polar Stereographic") "\n\tAzi, Sph&Ell\n\tsouth";
 
 
+enum Mode {
+    S_POLE = 0,
+    N_POLE = 1,
+    OBLIQ  = 2,
+    EQUIT  = 3
+};
+
 struct pj_opaque {
     double phits;
     double sinX1;
     double cosX1;
     double akm1;
-    int mode;
+    enum Mode mode;
 };
 
 #define sinph0  P->opaque->sinX1
@@ -21,10 +28,6 @@ struct pj_opaque {
 #define TOL 1.e-8
 #define NITER   8
 #define CONV    1.e-10
-#define S_POLE  0
-#define N_POLE  1
-#define OBLIQ   2
-#define EQUIT   3
 
 static double ssfn_ (double phit, double sinphi, double eccen) {
     sinphi *= eccen;