more fractions functionality.

src/util/variant.c

@@ -4,6 +4,9 @@
 #include <assert.h>
 #include <limits.h>
 
+const variant frac_zero = { .sa = { 0, 1 } };
+const variant frac_one = { .sa = { 1, 1 } };
+
 static int gcd(int a, int b) {
     const int primes[] = { 3, 5, 7, 11, 13, 17, 19, 23, 0 };
     int i = 0, g = 1, p = 2;
@@ -28,6 +31,10 @@ static int lcm(int a, int b) {
     return x;
 }
 
+bool frac_equal(variant a, variant b) {
+    return frac_sign(frac_sub(a, b)) == 0;
+}
+
 variant frac_make(int num, int den)
 {
     variant v;
@@ -64,3 +71,10 @@ variant frac_div(variant a, variant b)
 {
     return frac_make(a.sa[0] * b.sa[1], a.sa[1] * b.sa[0]);
 }
+
+int frac_sign(variant a) {
+    if (a.sa[0] == 0) return 0;
+    if (a.sa[0] > 0 && a.sa[1] > 0) return 1;
+    if (a.sa[0] < 0 && a.sa[1] < 0) return 1;
+    return -1;
+}

src/util/variant.h

@@ -2,6 +2,9 @@
 
 #ifndef STRUCT_VARIANT_H
 #define STRUCT_VARIANT_H
+
+#include <stdbool.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -21,11 +24,16 @@ extern "C" {
       VAR_FLOAT
   } variant_type;
 
+  extern const variant frac_zero;
+  extern const variant frac_one;
+
   variant frac_make(int num, int den);
   variant frac_add(variant a, variant b);
   variant frac_sub(variant a, variant b);
   variant frac_mul(variant a, variant b);
   variant frac_div(variant a, variant b);
+  int frac_sign(variant a);
+  bool frac_equal(variant a, variant b);
 
 #ifdef __cplusplus
 }

src/util/variant.test.c

@@ -20,8 +20,16 @@ static void test_fractions(CuTest *tc) {
     CuAssertIntEquals(tc, 1, a.sa[1]);
     a = frac_sub(a, a);
     CuAssertIntEquals(tc, 0, a.sa[0]);
-    a = frac_mul(a, b);
+    a = frac_sub(frac_one, a);
+    CuAssertIntEquals(tc, 1, a.sa[0]);
+    CuAssertIntEquals(tc, 1, a.sa[1]);
+    a = frac_mul(a, frac_zero);
     CuAssertIntEquals(tc, 0, a.sa[0]);
+    CuAssertIntEquals(tc, 1, frac_sign(frac_make(-1, -1)));
+    CuAssertIntEquals(tc, 1, frac_sign(frac_make(1, 1)));
+    CuAssertIntEquals(tc, -1, frac_sign(frac_make(-1, 1)));
+    CuAssertIntEquals(tc, -1, frac_sign(frac_make(1, -1)));
+    CuAssertIntEquals(tc, 0, frac_sign(frac_make(0, 1)));
 }
 
 CuSuite *get_variant_suite(void)