IMPROVES-i11 sequal now uses errno and returns -1,0,+1

cmp11sht.c

@@ -34,6 +34,7 @@
 #include <math.h>
 #include <ctype.h>
 #include <float.h>
+#include <errno.h>
 
 #define SBUFF 256 /* Max string size */
 
@@ -121,7 +122,15 @@ cmp11sht v20251221.0718 (C) 2025 by Ruben C. Benante (MIT Lic)\n\n"
     if(fenda == argv[1] || fendb == argv[2]) // string
     {
         if(opt==3) printf("cmp11sht: string\n");
+        errno = 0;
         res = sequal(argv[1], argv[2], delta, &ratio, s1, s2);
+        if(errno == EINVAL)
+            res = 3;                /* error → CLI exit 3 */
+        else if(res > 0)
+            res = 1;                /* a > b → CLI exit 1 */
+        else if(res < 0)
+            res = 2;                /* a < b → CLI exit 2 */
+        /* res == 0 stays 0 (equal) */
         if(opt==3) printf("result: ");
         if(opt) printf("%d\n", res);
         if(opt==3) printf("ratio: ");
@@ -132,6 +141,11 @@ cmp11sht v20251221.0718 (C) 2025 by Ruben C. Benante (MIT Lic)\n\n"
     {
         if(opt==3) printf("cmp11sht: float\n");
         res = fequal(a, b, delta);
+        if(res > 0)
+            res = 1;                /* a > b → CLI exit 1 */
+        else if(res < 0)
+            res = 2;                /* a < b → CLI exit 2 */
+        /* res == 0 stays 0 (equal) */
         if(opt==3) printf("result: ");
         if(opt) printf("%d\n", res);
         if(opt==3) printf("diff: ");
@@ -151,7 +165,7 @@ cmp11sht v20251221.0718 (C) 2025 by Ruben C. Benante (MIT Lic)\n\n"
 int fequal(float a, float b, float delta)
 {
     if(a < b - delta)
-        return 2;
+        return -1;
     if(a > b + delta)
         return  1;
 
@@ -160,16 +174,23 @@ int fequal(float a, float b, float delta)
 }
 
 /* ---------------------------------------------------------------------- */
-/* compare similarity between two strings
- * Return    0 if similar above given threshold
- *          -1 if a < b alphabetically
- *          +1 if a > b alphabetically
+/* compare similarity between two strings.
+ * Return:
+ *      0 if equal or similar above given threshold
+ *     -1 if a < b alphabetically (after normalization)
+ *     +1 if a > b alphabetically (after normalization)
+ * On error: sets errno = EINVAL and returns 0; result is undefined.
+ * Caller must reset errno = 0 before the call to detect errors.
  */
 int sequal(char *a, char *b, float thr, float *ratio, char *s1, char *s2)
 {
     int i;
 
-    if(!a || !b || !s1 || !s2 || !ratio) return 3; /* error sentinel */
+    if(!a || !b || !s1 || !s2 || !ratio)
+    {
+        errno = EINVAL;
+        return 0;
+    }
 
     // remove accents
     asciify(a, s1);
@@ -194,7 +215,7 @@ int sequal(char *a, char *b, float thr, float *ratio, char *s1, char *s2)
     *ratio = shit11(s1, s2);
     if(*ratio > thr)
         return 0;
-    return (i < 0)? 2 : 1;
+    return (i < 0)? -1 : 1;
 }
 
 /* ---------------------------------------------------------------------- */