Play around with a vector typeHEADmaster

Using _vectors_ as fundamental datatype could make for a really neat experience.

Imagine e.g.:

* fundamental arithmetic operations that apply to both vectors and scalars
* implicit component-wise or vector-wise operations
* scalar values as 1D vectors
* higher order functions to manipulate those vectors
    * `map` function that applies a (quoted?) word to all vector elements and returns the result
    * efficient parallel operations
* a rich library of vector manipulation functions
* or even: matrices as a fundamental datatype?
    * problem: probably harder to conveniently enter via a 1-D repl
* sound more and more like a RPN version of APL…

Back to reality, here is what this prototype actually adds:

* new `DList!int` based datatype alongside the existing int, string and bool types
* basic support for printing such values in a readable fashion
* new fundamental `:` word that constructs a vector of two elements
    * `1 2 :` yields `[1, 2]`
* adapted `+` and `*` to support component-wise operations
    * `1 2 : 3 +` yields `[4, 5]`

1 files changed, 5 insertions, 3 deletions

diff --git a/source/state/definition.d b/source/state/definition.d
index 6f41275..b8748ce 100644
--- a/source/state/definition.d
+++ b/source/state/definition.d
@@ -16,7 +16,8 @@ bool handle(Token token) {
 	return token.visit!(
 		(int    value) => handle(value),
 		(bool   value) => handle(value),
-		(string word ) => handle(word)
+		(string word ) => handle(word),
+		(DList!int  v) => handle(v)
 	);
 }
 
@@ -38,7 +39,8 @@ void register(DList!Token definition) {
 	definition.front.visit!(
 		(int    value) => wordToBeDefined = "",
 		(bool   value) => wordToBeDefined = "",
-		(string name ) => wordToBeDefined = name
+		(string name ) => wordToBeDefined = name,
+		(DList!int  v) => wordToBeDefined = ""
 	);
 
 	if ( wordToBeDefined == "" ) {
@@ -50,7 +52,7 @@ void register(DList!Token definition) {
 }
 
 template handle(T)
-if ( is(T == int) || is(T == bool) ) {
+if ( is(T == int) || is(T == bool) || is(T == DList!int) ) {
 	bool handle(T value) {
 		if ( definition.isNull ) {
 			return false;