add llist fns; fix missing colors bug; filter works on sets; other improvements

prelude.ld

@@ -247,6 +247,7 @@ fn foldr {
 & TODO: optimize these with base :conj!
 fn map {
 	"Maps a function over a list: returns a new list with elements that are the result of applying the function to each element in the original list. E.g., `map ([1, 2, 3], inc) &=> [2, 3, 4]`."
+	(f as :fn) -> map (f, _)
 	(f as :fn, xs) -> {
 		fn mapper (prev, curr) -> append (prev, f (curr))
 		fold (mapper, xs, [])
@@ -258,18 +259,21 @@ fn map {
 }
 
 fn filter {
-	"Takes a list and a predicate function, and returns a new list with only the items that produce truthy values when the function is called on them. E.g., `filter ([1, 2, 3, 4], odd?) &=> [1, 3]`."
-	(p? as :fn, xs) -> {
+	"Takes a list and a predicate function, and returns a new list with only the items that produce truthy values when the function is called on them. E.g., `filter ([1, 2, 3, 4], odd?) &=> [1, 3]`. Also works on sets."
+	(p? as :fn) -> filter(p?, _)
+	(p? as :fn, xs as list) -> {
 		fn filterer (filtered, x) -> if p? (x)
 			then append (filtered, x)
 			else filtered
 		fold (filterer, xs, [])
 	}
+	(p? as :fn, xs as :set) -> do xs > list > filter (p?, _) > set
 }
 
 fn keep {
 	"Takes a list and returns a new list with any `nil` values omitted."
-	(xs) -> filter (some?, xs)
+	(xs as :list) -> filter (some?, xs)
+	(xs as :set) -> filter (some?, xs)
 }
 
 fn append {
@@ -313,6 +317,7 @@ fn contains? {
 	"Returns true if a set or list contains a value."
 	(value, s as :set) -> bool (base :get	(s, value))
 	(value, l as :list) -> contains? (value, set (list))
+	(key, d as :dict) -> do d > key > some?
 }
 
 fn omit {
@@ -1114,6 +1119,7 @@ let colors = #{
 	:black (0, 0, 0, 255)
 	:silver (192, 192, 192, 255)
 	:gray (128, 128, 128, 255)
+	:grey (128, 128, 128, 255)
 	:white (255, 255, 255, 255)
 	:maroon (128, 0, 0, 255)
 	:red (255, 0, 0, 255)
@@ -1129,6 +1135,8 @@ let colors = #{
 	:aqua (0, 255, 255, 255)
 }
 
+let colours = colors
+
 & the initial turtle state
 let turtle_init = #{
 	:position (0, 0) & let's call this the origin for now
@@ -1196,12 +1204,13 @@ let pd! = pendown!
 
 fn pencolor! {
 	"Changes the turtle's pen color. Takes a single grayscale value, an rgb tuple, or an rgba tuple. Alias: pc!"
-	(color as :keyword) -> add_command! ((:pencolor, color))
+	(color as :keyword) -> if contains? (colors, color) then add_command! ((:pencolor, color)) else panic! "Ludus doesn't know about the color {color}"
 	(gray as :number) -> add_command! ((:pencolor, (gray, gray, gray, 255)))
 	((r as :number, g as :number, b as :number)) -> add_command! ((:pencolor, (r, g, b, 255)))
 	((r as :number, g as :number, b as :number, a as :number)) -> add_command! ((:pencolor, (r, g, b, a)))
 }
 
+let pencolour! = pencolor!
 let pc! = pencolor!
 
 fn penwidth! {
@@ -1213,7 +1222,7 @@ let pw! = penwidth!
 
 fn background! {
 	"Sets the background color behind the turtle and path. Alias: bg!"
-	(color as :keyword) -> add_command! ((:background, color))
+	(color as :keyword) -> if contains? (colors, color) then add_command! ((:background, color)) else panic! "Ludus doesn't know about the color {color}"
 	(gray as :number) -> add_command! ((:background, (gray, gray, gray, 255)))
 	((r as :number, g as :number, b as :number)) -> add_command! ((:background, (r, g, b, 255)))
 	((r as :number, g as :number, b as :number, a as :number)) -> add_command! ((:background, (r, g, b, a)))
@@ -1322,6 +1331,26 @@ fn penwidth {
 	() -> do turtle_state > unbox > :penwidth
 }
 
+fn cons {
+	"Old-timey lisp `cons`. `Cons`tructs a tuple out of two arguments."
+	(x, y) -> (x, y)
+}
+
+fn car {
+	"Old-timey lisp `car`. Stands for 'contents of the address register.' Returns the first element in a `cons`ed pair (or any two-tuple)."
+	((x, _)) -> x
+}
+
+fn cdr {
+	"Old-timey list `cdr`. Stands for 'contents of the decrement register.' Returns the second element in a `cons`ed pair, usually representing the rest of the list."
+	((_, x)) -> x
+}
+
+fn llist {
+	"Makes an old-timey linked list of its arguments, of LISt Processor fame."
+	(...xs) -> foldr (cons, xs, nil)
+}
+
 box state = nil
 
 pkg Prelude {
@@ -1345,12 +1374,15 @@ pkg Prelude {
 	bool? & bool
 	box? & boxes
 	butlast & lists strings tuples
+	car & llist
+	cdr & llist
 	ceil & math
 	chars & strings
 	clear! & turtles
 	coll? & dicts lists sets tuples
 	colors & turtles
 	concat & string list set 
+	cons & llist
 	contains? & list set
 	cos & math
 	count & string list set tuple dict