September 2017 Update

Task/Matrix-multiplication/Jq/matrix-multiplication.jq

@@ -0,0 +1,18 @@
+def dot_product(a; b):
+  a as $a | b as $b
+  | reduce range(0;$a|length) as $i (0; . + ($a[$i] * $b[$i]) );
+
+# transpose/0 expects its input to be a rectangular matrix (an array of equal-length arrays)
+def transpose:
+  if (.[0] | length) == 0 then []
+  else [map(.[0])] + (map(.[1:]) | transpose)
+  end ;
+
+# A and B should both be numeric matrices, A being m by n, and B being n by p.
+def multiply(A; B):
+  A as $A | B as $B
+  | ($B[0]|length) as $p
+  | ($B|transpose) as $BT
+  | reduce range(0; $A|length) as $i
+       ([]; reduce range(0; $p) as $j
+         (.; .[$i][$j] = dot_product( $A[$i]; $BT[$j] ) )) ;