(*
	lengthOfList[list] : list の長さを求める
		list : 長さを求めるリスト ( cf. Length )
*)


lengthOfList[{}] := 0
lengthOfList[list_] := lengthOfList[Rest[list]] + 1

(*
	lengthOfList[{}]
	lengthOfList[{a,b,c}]
*)

(*
lengthOfList[list_] := 
	If[
		list == {},
		0,
		lengthOfList[Rest[list]] + 1
	]
*)

(*
	findMember[list,member] : list の中の member の位置を探す
		list : 要素を探すリスト ( cf. Length )
*)

findMember[list_,member_] := findMember[list,member,1]

findMember[{},member_,pos_] := -1
findMember[list_,member_,pos_] :=
	If[
		First[list] == member,
		pos,
		findMember[Rest[list],member,pos + 1]
	]

(*
	findMember[{"a","b","c","d"}, "c"]
	findMember[{"a","b","c","d"}, "x"]
*)