; lisp - a library of LISP-like primitives for Power LOGO
; Tony L Belding

if namep "lispnames [ unbury :lispnames ] [ ]

make "remove [
	procedure [ [ :card :deck ] ]

	; removes all occurences of object CARD from object DECK

	if not memberp :card :deck [
		op :deck
	] [
		if = :card first :deck [
			op remove :card bf :deck
		] [
			op fput first :deck remove :card bf :deck
		]
	]
]

make "delete [
	procedure [ [ :card :deck ] ]

	; a shortcut for:  make "object remove :key :object
	;    instead use:  delete :key "object

	; This is not quirky about the first item like LISP delete is.

	make :deck remove :card thing :deck
	op thing :deck
]

make "push [
	procedure [ [ :Item :List ] ]

	; push adds an item to the beginning of a list
	make :List firstput :Item thing :List
	op thing :List
]

make "pop [
	procedure [ [ :List ] [ ] [ :Item ] ]

	; pop removes the first item from a list
	make "Item first thing :List
	make :List butfirst thing :List
	op :Item
]

make "assoc [
	procedure [ [ :key :alist ] ]

	; equivalent to LISP ASSOC primitive
	; uses a key value to extract a sublist from an association list

	if emptyp :alist
		[ op [ ] ] [ ]
	if ( = :key first first :alist ) [
		op first :alist
	] [
		op assoc :key butfirst :alist
	]
]

make "lisp [ procedure [ ] ]

make "lispnames [ lispnames remove delete push pop assoc lisp ]

bury :lispnames

; end of listing