Data commit

Task/Forward-difference/E/forward-difference.e

@@ -0,0 +1,32 @@
+pragma.enable("accumulator")
+/** Single step. */
+def forwardDifference(seq :List) {
+    return accum [] for i in 0..(seq.size() - 2) {
+        _.with(seq[i + 1] - seq[i])
+    }
+}
+
+/** Iterative implementation of the goal. */
+def nthForwardDifference1(var seq :List, n :(int >= 0)) {
+    for _ in 1..n { seq := forwardDifference(seq) }
+    return seq
+}
+
+/** Imperative implementation of the goal. */
+def nthForwardDifference2(seq :List, n :(int >= 0)) {
+  def buf := seq.diverge()
+  def finalSize := seq.size() - n
+  for lim in (finalSize..!seq.size()).descending() {
+    for i in 0..!lim {
+      buf[i] := buf[i + 1] - buf[i]
+    }
+  }
+  return buf.run(0, finalSize)
+}
+
+? def sampleData := [90, 47, 58, 29, 22, 32, 55, 5, 55, 73]
+> for n in 0..10 {
+>   def r1 := nthForwardDifference1(sampleData, n)
+>   require(r1 == nthForwardDifference2(sampleData, n))
+>   println(r1)
+> }