Initial data commit

Task/Approximate-equality/Go/approximate-equality.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+    "fmt"
+    "log"
+    "math/big"
+)
+
+func max(a, b *big.Float) *big.Float {
+    if a.Cmp(b) > 0 {
+        return a
+    }
+    return b
+}
+
+func isClose(a, b *big.Float) bool {
+    relTol := big.NewFloat(1e-9) // same as default for Python's math.isclose() function
+    t := new(big.Float)
+    t.Sub(a, b)
+    t.Abs(t)
+    u, v, w := new(big.Float), new(big.Float), new(big.Float)
+    u.Mul(relTol, max(v.Abs(a), w.Abs(b)))
+    return t.Cmp(u) <= 0
+}
+
+func nbf(s string) *big.Float {
+    n, ok := new(big.Float).SetString(s)
+    if !ok {
+        log.Fatal("invalid floating point number")
+    }
+    return n
+}
+
+func main() {
+    root2 := big.NewFloat(2.0)
+    root2.Sqrt(root2)
+    pairs := [][2]*big.Float{
+        {nbf("100000000000000.01"), nbf("100000000000000.011")},
+        {nbf("100.01"), nbf("100.011")},
+        {nbf("0").Quo(nbf("10000000000000.001"), nbf("10000.0")), nbf("1000000000.0000001000")},
+        {nbf("0.001"), nbf("0.0010000001")},
+        {nbf("0.000000000000000000000101"), nbf("0.0")},
+        {nbf("0").Mul(root2, root2), nbf("2.0")},
+        {nbf("0").Mul(nbf("0").Neg(root2), root2), nbf("-2.0")},
+        {nbf("100000000000000003.0"), nbf("100000000000000004.0")},
+        {nbf("3.14159265358979323846"), nbf("3.14159265358979324")},
+    }
+    for _, pair := range pairs {
+        s := "≉"
+        if isClose(pair[0], pair[1]) {
+            s = "≈"
+        }
+        fmt.Printf("% 21.19g %s %- 21.19g\n", pair[0], s, pair[1])
+    }
+}