September 2017 Update

Task/Matrix-arithmetic/Jq/matrix-arithmetic-1.jq

@@ -0,0 +1,18 @@
+# Eliminate row i and row j
+def except(i;j):
+  reduce del(.[i])[] as $row ([]; . + [$row | del(.[j]) ] );
+
+def det:
+  def parity(i): if i % 2 == 0 then 1 else -1 end;
+  if length == 1 and (.[0] | length) == 1 then .[0][0]
+  else . as $m
+    | reduce range(0; length) as $i
+        (0; . + parity($i) * $m[0][$i] * ( $m | except(0;$i) | det) )
+  end ;
+
+def perm:
+  if length == 1 and (.[0] | length) == 1 then .[0][0]
+  else . as $m
+    | reduce range(0; length) as $i
+        (0; . + $m[0][$i] * ( $m | except(0;$i) | perm) )
+  end ;