A-M baby

Task/Forward-difference/D/forward-difference-1.d

@@ -0,0 +1,20 @@
+import std.stdio;
+
+T[] forwardDifference(T)(in T[] data, in int level) pure nothrow
+    in {
+        assert(level >= 0 && level < data.length);
+    } body {
+        //auto result = data.dup; // not nothrow
+        auto result = data ~ []; // slower
+        foreach (i; 0 .. level)
+            foreach (j, ref el; result[0 .. $ - i - 1])
+                el = result[j + 1] - el;
+        result.length -= level;
+        return result;
+    }
+
+void main() {
+    auto data = [90.5, 47, 58, 29, 22, 32, 55, 5, 55, 73.5];
+    foreach (level; 0 .. data.length)
+        writeln(forwardDifference(data, level));
+}

Task/Forward-difference/D/forward-difference-2.d

@@ -0,0 +1,13 @@
+import std.stdio, std.algorithm, std.range, std.array;
+
+auto forwardDifference(Range)(Range d, in int level) {
+    foreach (_; 0 .. level)
+        d = zip(d[1 .. $], d).map!q{ a[0] - a[1] }().array();
+    return d;
+}
+
+void main() {
+    auto data = [90.5, 47, 58, 29, 22, 32, 55, 5, 55, 73.5];
+    foreach (level; 0 .. data.length)
+        writeln(forwardDifference(data, level));
+}

Task/Forward-difference/D/forward-difference-3.d

@@ -0,0 +1,12 @@
+import std.stdio;
+
+T[] forwardDifference(T)(T[] s, in int n) pure {
+    foreach (_; 0 .. n)
+        s[] -= s[1 .. $];
+    return s[0 .. $ - n];
+}
+void main() {
+    immutable A = [90.5, 47, 58, 29, 22, 32, 55, 5, 55, 73.5];
+    foreach (level; 0 .. A.length)
+        writeln(forwardDifference(A.dup, level));
+}

Task/Forward-difference/D/forward-difference-4.d

@@ -0,0 +1,8 @@
+import std.stdio, std.range;
+
+void main() {
+  auto D = [90.5, 47, 58, 29, 22, 32, 55, 5, 55, 73.5];
+  auto R = recurrence!q{(a[n-1].dup[] -= a[n-1][1..$])[0..$-1]}(D);
+  foreach (di; take(R, D.length))
+    writeln(di);
+}