Data commit

Task/Tropical-algebra-overloading/Go/tropical-algebra-overloading.go

@@ -0,0 +1,94 @@
+package main
+
+import (
+    "fmt"
+    "log"
+    "math"
+)
+
+var MinusInf = math.Inf(-1)
+
+type MaxTropical struct{ r float64 }
+
+func newMaxTropical(r float64) MaxTropical {
+    if math.IsInf(r, 1) || math.IsNaN(r) {
+        log.Fatal("Argument must be a real number or negative infinity.")
+    }
+    return MaxTropical{r}
+}
+
+func (t MaxTropical) eq(other MaxTropical) bool {
+    return t.r == other.r
+}
+
+// equivalent to ⊕ operator
+func (t MaxTropical) add(other MaxTropical) MaxTropical {
+    if t.r == MinusInf {
+        return other
+    }
+    if other.r == MinusInf {
+        return t
+    }
+    return newMaxTropical(math.Max(t.r, other.r))
+}
+
+// equivalent to ⊗ operator
+func (t MaxTropical) mul(other MaxTropical) MaxTropical {
+    if t.r == 0 {
+        return other
+    }
+    if other.r == 0 {
+        return t
+    }
+    return newMaxTropical(t.r + other.r)
+}
+
+// exponentiation function
+func (t MaxTropical) pow(e int) MaxTropical {
+    if e < 1 {
+        log.Fatal("Exponent must be a positive integer.")
+    }
+    if e == 1 {
+        return t
+    }
+    p := t
+    for i := 2; i <= e; i++ {
+        p = p.mul(t)
+    }
+    return p
+}
+
+func (t MaxTropical) String() string {
+    return fmt.Sprintf("%g", t.r)
+}
+
+func main() {
+    // 0 denotes ⊕ and 1 denotes ⊗
+    data := [][]float64{
+        {2, -2, 1},
+        {-0.001, MinusInf, 0},
+        {0, MinusInf, 1},
+        {1.5, -1, 0},
+        {-0.5, 0, 1},
+    }
+    for _, d := range data {
+        a := newMaxTropical(d[0])
+        b := newMaxTropical(d[1])
+        if d[2] == 0 {
+            fmt.Printf("%s ⊕ %s = %s\n", a, b, a.add(b))
+        } else {
+            fmt.Printf("%s ⊗ %s = %s\n", a, b, a.mul(b))
+        }
+    }
+
+    c := newMaxTropical(5)
+    fmt.Printf("%s ^ 7 = %s\n", c, c.pow(7))
+
+    d := newMaxTropical(8)
+    e := newMaxTropical(7)
+    f := c.mul(d.add(e))
+    g := c.mul(d).add(c.mul(e))
+    fmt.Printf("%s ⊗ (%s ⊕ %s) = %s\n", c, d, e, f)
+    fmt.Printf("%s ⊗ %s ⊕ %s ⊗ %s = %s\n", c, d, c, e, g)
+    fmt.Printf("%s ⊗ (%s ⊕ %s) == %s ⊗ %s ⊕ %s ⊗ %s is %t\n", c, d, e, c, d, c, e, f.eq(g))
+}