Another update from ingydotnet^djgoku

Task/Identity-matrix/Go/identity-matrix-1.go

@@ -1,18 +1,19 @@
 package main
 
-import "fmt"
+import (
+    "fmt"
 
-func main() {
-    fmt.Println(I(3))
-}
+    "github.com/gonum/matrix/mat64"
+)
 
-func I(n int) [][]float64 {
-    m := make([][]float64, n)
-    a := make([]float64, n*n)
+func eye(n int) *mat64.Dense {
+    m := mat64.NewDense(n, n, nil)
     for i := 0; i < n; i++ {
-        a[i] = 1
-        m[i] = a[:n]
-        a = a[n:]
+        m.Set(i, i, 1)
     }
     return m
 }
+
+func main() {
+    fmt.Println(mat64.Formatted(eye(3)))
+}

Task/Identity-matrix/Go/identity-matrix-2.go

@@ -1,18 +1,11 @@
 package main
 
-import "fmt"
+import (
+    "fmt"
 
-type matrix []float64
+    mat "github.com/skelterjohn/go.matrix"
+)
 
 func main() {
-    fmt.Println(I(3))
-}
-
-func I(n int) matrix {
-    m := make(matrix, n*n)
-    n++
-    for i := 0; i < len(m); i += n {
-        m[i] = 1
-    }
-    return m
+    fmt.Println(mat.Eye(3))
 }

Task/Identity-matrix/Go/identity-matrix-3.go

@@ -1,11 +1,17 @@
 package main
 
-import (
-    "fmt"
-
-    mat "github.com/skelterjohn/go.matrix"
-)
+import "fmt"
 
 func main() {
-    fmt.Println(mat.Eye(3))
+    fmt.Println(I(3))
+}
+
+func I(n int) [][]float64 {
+    m := make([][]float64, n)
+    for i := 0; i < n; i++ {
+        a := make([]float64, n)
+        a[i] = 1
+        m[i] = a
+    }
+    return m
 }

Task/Identity-matrix/Go/identity-matrix-4.go

@@ -0,0 +1,18 @@
+package main
+
+import "fmt"
+
+func main() {
+    fmt.Println(I(3))
+}
+
+func I(n int) [][]float64 {
+    m := make([][]float64, n)
+    a := make([]float64, n*n)
+    for i := 0; i < n; i++ {
+        a[i] = 1
+        m[i] = a[:n]
+        a = a[n:]
+    }
+    return m
+}

Task/Identity-matrix/Go/identity-matrix-5.go

@@ -0,0 +1,34 @@
+package main
+
+import "fmt"
+
+type matrix []float64
+
+func main() {
+    n := 3
+    m := I(n)
+    // dump flat represenation
+    fmt.Println(m)
+
+    // function x turns a row and column into an index into the
+    // flat representation.
+    x := func(r, c int) int { return r*n + c }
+
+    // access m by row and column.
+    for r := 0; r < n; r++ {
+        for c := 0; c < n; c++ {
+            fmt.Print(m[x(r, c)], " ")
+        }
+        fmt.Println()
+    }
+}
+
+func I(n int) matrix {
+    m := make(matrix, n*n)
+    // a fast way to initialize the flat representation
+    n++
+    for i := 0; i < len(m); i += n {
+        m[i] = 1
+    }
+    return m
+}