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_gnom.c b/src/PJ_gnom.c
index 2aedefec..e5822f4f 100644
--- a/src/PJ_gnom.c
+++ b/src/PJ_gnom.c
@@ -6,15 +6,18 @@
 PROJ_HEAD(gnom, "Gnomonic") "\n\tAzi, Sph.";
 
 #define EPS10  1.e-10
-#define N_POLE 0
-#define S_POLE 1
-#define EQUIT  2
-#define OBLIQ  3
+
+enum Mode {
+    N_POLE = 0,
+    S_POLE = 1,
+    EQUIT  = 2,
+    OBLIQ  = 3
+};
 
 struct pj_opaque {
     double  sinph0;
     double  cosph0;
-    int     mode;
+    enum Mode mode;
 };