June 2018 Update

Task/Vector-products/Factor/vector-products.factor

@@ -0,0 +1,31 @@
+USING: arrays io locals math prettyprint sequences ;
+IN: rosetta-code.vector-products
+
+: dot-product ( a b -- dp ) [ * ] 2map sum ;
+
+:: cross-product ( a b -- cp )
+    a first :> a1 a second :> a2 a third :> a3
+    b first :> b1 b second :> b2 b third :> b3
+    a2 b3 * a3 b2 * - ! X
+    a3 b1 * a1 b3 * - ! Y
+    a1 b2 * a2 b1 * - ! Z
+    3array ;
+
+: scalar-triple-product ( a b c -- stp )
+    cross-product dot-product ;
+
+: vector-triple-product ( a b c -- vtp )
+    cross-product cross-product ;
+
+[let
+    { 3 4 5 }      :> a
+    { 4 3 5 }      :> b
+    { -5 -12 -13 } :> c
+    "a: " write a .
+    "b: " write b .
+    "c: " write c . nl
+    "a . b: " write a b dot-product .
+    "a x b: " write a b cross-product .
+    "a . (b x c): " write a b c scalar-triple-product .
+    "a x (b x c): " write a b c vector-triple-product .
+]