September 2017 Update

Task/Forward-difference/Jq/forward-difference-1.jq

@@ -0,0 +1,8 @@
+# If n is a non-negative number and if input is
+# a (possibly empty) array of numbers,
+# emit an array, even if the input list is too short:
+def ndiff(n):
+  if n==0 then .
+  elif n == 1 then . as $in | [range(1;length) | $in[.] - $in[.-1]]
+  else ndiff(1) | ndiff(n-1)
+  end;

Task/Forward-difference/Jq/forward-difference-2.jq

@@ -0,0 +1,3 @@
+def s: [90, 47, 58, 29, 22, 32, 55, 5, 55, 73];
+
+range(0;12) as $i | (s|ndiff($i))

Task/Forward-difference/Jq/forward-difference-3.jq

@@ -0,0 +1,13 @@
+$ jq -c -n -f forward-difference.jq
+[90,47,58,29,22,32,55,5,55,73]
+[-43,11,-29,-7,10,23,-50,50,18]
+[54,-40,22,17,13,-73,100,-32]
+[-94,62,-5,-4,-86,173,-132]
+[156,-67,1,-82,259,-305]
+[-223,68,-83,341,-564]
+[291,-151,424,-905]
+[-442,575,-1329]
+[1017,-1904]
+[-2921]
+[]
+[]