Matrix multiplication: Difference between revisions

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@@ Line 714: / Line 714: @@
 =={{header|D}}==
-<lang d>import std.stdio: writefln;
+<lang d>import std.stdio, std.string;
-import std.string: format, join;
-T[][] matrixMul(T)(T[][] m1, T[][] m2) {
+pure bool isRectangular(T)(const T[][] matrix) {
-    bool isRectangular(T[][] matrix) {
+    foreach (row; matrix)
-        foreach (row; matrix)
+        if (row.length != matrix[0].length)
-            if (row.length != matrix[0].length)
+            return false;
-                return false;
+    return true;
+}
-        return true;
-    }
-    T[][] result;
-    if (isRectangular(m1) && isRectangular(m2) && m1[0].length == m2.length) {
-        result = new T[][](m1.length, m2[0].length);
+T[][] matrixMul(T)(T[][] m1, T[][] m2)
+    in {
+        assert(isRectangular(m1) && isRectangular(m2) &&
+               m1[0].length == m2.length);
+    } body {
+        auto result = new T[][](m1.length, m2[0].length);
         foreach (i, m1_row_i; m1)
-            for (int j; j < m2[0].length; j++) {
+            foreach (j; 0 .. m2[0].length) {
                 T aux = 0;
                 foreach (k, m2_row_k; m2)
@@ Line 736: / Line 736: @@
                 result[i][j] = aux;
             }
-    } else
+        return result;
+    }
-        throw new Exception("matrixMul Error");
-    return result;
-}
 string prettyPrint(T)(T[][] matrix) {
@@ Line 749: / Line 747: @@
 void main() {
-    float[][] a = [[1, 2], [3, 4], [3, 6]];
+    enum a = [[1, 2], [3, 4], [3, 6]];
-    float[][] b = [[-3, -8, 3,], [-2, 1, 4]];
+    enum b = [[-3, -8, 3,], [-2, 1, 4]];
+    writeln("A = \n", prettyPrint(a));
-    writefln("A = \n", prettyPrint(a));
+    writeln("\nB = \n", prettyPrint(b));
-    writefln("\nB = \n", prettyPrint(b));
+    writeln("\nA * B = \n", prettyPrint(matrixMul(a, b)));
-    writefln("\nA * B = \n", prettyPrint(matrixMul(a, b)));
 }</lang>
+Output:
+<pre>A =
+[[1,2],
+ [3,4],
+ [3,6]]
+B =
+[[-3,-8,3],
+ [-2,1,4]]
+A * B =
+[[-7,-6,11],
+ [-17,-20,25],
+ [-21,-18,33]]</pre>
 =={{header|ELLA}}==
 Sample originally from ftp://ftp.dra.hmg.gb/pub/ella (a now dead link) - Public release.