Data commit

Task/Monads-Writer-monad/Go/monads-writer-monad.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+type mwriter struct {
+    value float64
+    log   string
+}
+
+func (m mwriter) bind(f func(v float64) mwriter) mwriter {
+    n := f(m.value)
+    n.log = m.log + n.log
+    return n
+}
+
+func unit(v float64, s string) mwriter {
+    return mwriter{v, fmt.Sprintf("  %-17s: %g\n", s, v)}
+}
+
+func root(v float64) mwriter {
+    return unit(math.Sqrt(v), "Took square root")
+}
+
+func addOne(v float64) mwriter {
+    return unit(v+1, "Added one")
+}
+
+func half(v float64) mwriter {
+    return unit(v/2, "Divided by two")
+}
+
+func main() {
+    mw1 := unit(5, "Initial value")
+    mw2 := mw1.bind(root).bind(addOne).bind(half)
+    fmt.Println("The Golden Ratio is", mw2.value)
+    fmt.Println("\nThis was derived as follows:-")
+    fmt.Println(mw2.log)
+}