% Prolog procedures for asking user questions.  Included by shell programs.
%


:-[-'stdStuff.pro'].
:-op(100,xfx,for).
%
% Question-asking procedures.
%

% Sample Questions

quest(qOne,'What is your name?').
quest(qTwo,'What is your quest?').
quest(qThree,'What is your favourite colour?').

% Asks a question and accepts any prolog term as an answer.
%
ask(Q,A):-sOut<<Q,read(A).

% Calls unstar to replace * in question with S and print question, 
% then gets any answer.
%
ask(Q,S,A):-unStar(Q,S),read(A).

% Prints string obtained by replacing * in Q with S.  For example, the
% goal unStar('What color is *?',object1) would result in "What color
% is object1?" being printed on the terminal.
%
unStar(Q,S):-Qstr<<Q,Sstr<<S,
	(
	 append(Before,[42|After],Qstr),
	 sOut<<Before<<Sstr<<After<<nl
	;
         sOut<<Qstr<<nl
	).

% Asks question Q with * replaced by S; A is unified with answer, R
% specifies types of valid answers.
%
askAndCheck(Q,S,R,Ans):-unStar(Q,S),askAndCheck1(R,A),!,A=Ans.
askAndCheck1(isNum(Limits),A):-
	(  true  ;  repeat,sOut<<'Please enter a number.'<<nl  ),
	read(A),number(A),
	(  Limits=range(Low,High),A>=Low,A=<High
	   ;
	   Limits=min(Low),A>=Low ; Limits=max(High),A=<High ; Limits=none
	   ; 
	   write('Number out of range.'),nl,fail
	),!.
askAndCheck1(isEnum(List),A):-getAns(List,A).
askAndCheck1(yesNo,A):-getAns([true for yes,false for no],A).
askAndCheck1(yesNoWhy,A):-getAns([true for yes,false for no,why for 'why?'],A).
askAndCheck1(isString,A):-
	( true ; repeat,sOut<<'Enter an atom.'<<nl ),
	read(A),atomic(A).
askAndCheck1(X,error):-sOut<<'Warning: validation check '<<X<<' unknown'.
getAns(List,Ans):-
	append(List,[unknown for 'Don''t know.'],NewList),
	getAns1(NewList,Ans,0).
getAns1([],AnsNum,HighestNum):-
	repeat,sOut<<'Enter choice number: ',read(AnsNum),
	integer(AnsNum),AnsNum > 0,AnsNum =< HighestNum,nl.
getAns1([Code for Choice|More],AnsCode,PrevItem):-
	Item is PrevItem+1,sOut<<Item<<') '<<Choice<<nl,	
	getAns1(More,AnsCodeB,Item),
	(
		AnsCodeB=Item,AnsCode=Code
		;
		AnsCode=AnsCodeB
	).