jScheme/test2.html at master · jhtwong/jScheme · GitHub

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<html>

<body>
<table width=100%><tr>
<td align=left><font size=+3><b>jScheme </b></font><font size=+2>0.27</font>
<td align=left><form><input><input></form>
<td align=right><font size=+1>by Joseph Wong</font></tr></table>
</body>

<script language="JavaScript1.2">

// Version 0.27 - added cons,symbol counters
// (1-31-99)
// Version 0.26 - fixed stack overflow in IE5 due to not being able to parse '( )
// (11-23-98)
// Version 0.25 - fixed set-car!, set-cdr! so that the first arg can be a form that returns a pair-type lvalue
// (11-22-98)
// Version 0.24 - added native, set-car!, set-cdr!
// (03-12-98)
// Version 0.23 - first public release
// (02-16-98)

conscount=0;
symcount=0;

tq=false;  // trace quote

function message(s) { top.frames[1].document.writeln(s,"<BR>"); }

spacechar="  ".charAt(0);

message("<b>Initializing Scheme functionality components for JavaScript 1.2 ...</b>");
message("<b>Copyright (c) Joseph Wong, 1998</b>");
message("Implementing pair structure...");

function Pair(a,d) {
	this.elemA = a;
	this.elemD = d;
}

message("Implementing 'cons'...");

function cons(a,d) {
	conscount++;
	document.forms[0].elements[0].value="cons count: "+conscount;
	return new Pair(a,d);
}

message("Implementing 'car'...");

function car(p) {
	return p.elemA;
}

message("Implementing 'cdr'...");

function cdr(p) {
	return p.elemD;
}

message("Implementing 'setcar'...");

function setcar(p,x) {
	p.elemA=x;
}

message("Implementing 'setcdr'...");

function setcdr(p,x) {
	p.elemD=x;
}

message("Implementing list structure...");
message("Implementing 'list'...");

function list() {
	l=null;
	for (var i=list.arguments.length-1; i>=0; i--)
		l=cons(list.arguments[i],l);
	return l;
}

message("Implementing 'listtail'...");

function listtail(l,i) {
	if (i==0) {
		return l;
	} else {
		return listtail(cdr(l),i-1);
	}
}

message("Implementing 'listref'...");

function listref(l,i) {
	return car(listtail(l,i));
}

message("Implementing symbols...");

function issymbol(sym) {
	if (ispairobj(sym)) { return (car(sym)=="**symbol**"); } else { return false; }
}

symboltostring=cdr;

message("Implementing 'quote'...");

function findsublist(st) {
	var s=st;
	s=s.substring(1,s.length-1);
	var parendepth=0;
	var quoteon=false;
	var i=0;
	do {
		if (s.charAt(i)=='"') {
			quoteon=!quoteon;
		}
		if (!quoteon) {
 		if (s.charAt(i)=="(") {
			parendepth++;
		} else {
			if (s.charAt(i)==")") {
				parendepth--;
			}
		}}
		i++
	} while (parendepth>0);
	var ret1="("+s.substring(1,i-1)+")";
	var ret2=s.substring(i,s.length);
	var oldret2=ret2;
	do {
		oldret2=ret2;
		if (ret2.charAt(0)==spacechar) { ret2=ret2.substring(1,ret2.length); }
	} while (oldret2 != ret2);

	ret2="("+ret2+")"
	return new Array(ret1,ret2);
}

function findquotedsublist(st) {
	var s=st;
	s=s.substring(1,s.length-1);
	var parendepth=0;
	var i=1;
	do {
		if (s.charAt(i)=="(") {
			parendepth++;
		} else {
			if (s.charAt(i)==")") {
				parendepth--;
			}
		}
		i++
	} while (parendepth>0);
	var ret1="("+s.substring(2,i-1)+")";
	var ret2=s.substring(i,s.length);
	var oldret2=ret2;
	do {
		oldret2=ret2;
		if (ret2.charAt(0)==spacechar) { ret2=ret2.substring(1,ret2.length); }
	} while (oldret2 != ret2);

	ret2="("+ret2+")"
	return new Array(ret1,ret2);
}


function codestring(st) {
	var s=st;
	var quoteon=false;
	for (var i=0;i < s.length; i++)
		if (s.charAt(i)=='"') {
			quoteon=!quoteon;
		} else {
		if ((s.charAt(i)==spacechar) && quoteon) {
			s=s.substring(0,i)+"**spacechar**"+s.substring(i+1,s.length);
			i+=12;
		}
	}
	return s;
}

message("           ...list parser...");
function parselist(st) {
	var s=st;
	while ((s.charAt(1)==" ") ||
		 (s.charAt(1)=="\f") ||
		 (s.charAt(1)=="\r") ||
		 (s.charAt(1)=="\n") ||
		 (s.charAt(1)=="\t"))
	{
		s="("+s.substring(2,s.length);
	}

	s=codestring(st);

	var olds=s;
	do {
		olds=s;
		s=s.replace(/\s+/,spacechar);
	} while (olds != s);

	if (s=="()" || s=="( )") { // second case to cover for IE5
		return null;
	} else {
		if (s.charAt(1)=="(") {
			var e=findsublist(s);
			var first=e[0];
			var rest=e[1];
			return cons(quote(first),quote(rest));
		} else if (s.substring(1,3)=="'(") {
			var e=findquotedsublist(s);
			var first=list(quote("quote"),quote(e[0]));
			var rest=e[1];
			return cons(first,quote(rest));
		} else {
			var args=s.substring(1,s.length-1).split(" ");
			var first=args[0]
			var rest="";
			for(var i=1;i < args.length; i++)
				rest=rest+args[i]+spacechar;
			if (first==".") {
				return quote(rest);
			} else {
				return cons(quote(first),quote("("+rest+")"));
			}
		}
	}
}

message("           ...string parser...");

function parsestring(st) {
	var s=st;
	for (var i=0;i < s.length; i++)
		if (s.substr(i,13)=='**spacechar**') {
			s=s.substring(0,i)+spacechar+s.substring(i+13,s.length);
			i-=13;
		}
	return s;
}

function quote(st) {
	var s=st;
	var olds=s;
	do {
		olds=s;
		if (s.charAt(s.length-1)==spacechar) {
			s=s.substring(0,s.length-1);
		}
	} while (olds != s);

//
	if (tq) { message("quoting: '"+s+"'") };
//
	var ret;
	if (!isNaN(Number(s)))
		{ ret=Number(s); return ret; }
	else if (s.charAt(0)=='"')
		{ ret=parsestring(s.substring(s.indexOf('"')+1,s.lastIndexOf('"'))); return ret; }
	else if (s.charAt(0)=="'")
		{ ret=list(quote("quote"),quote(s.substring(1,s.length))); return ret; }
	else if (s.charAt(0) != "(")
		{ symcount++; document.forms[0].elements[1].value="symbols count: "+symcount;
              ret=cons("**symbol**",s.toLowerCase()); return ret; }
	else { ret=parselist(s); return ret; }
}

message("Implementing type checkers...");

function ispairobj(q) {
	if ((typeof(q)=="object") && (q!=null)) { return (q.elemA != "".elemA) } else { return false; }
}

function ispair(q) {
	if (ispairobj(q)) { return !issymbol(q); } else { return false; }
}

function symbolequal(a,b) {
	return (issymbol(a) && issymbol(b) && (cdr(a).toLowerCase()==cdr(b)));
}

function isboolean(x) {
	return (typeof(x)=="boolean");
}

function isstring(x) {
	return (typeof(x)=="string");
}

function isnumber(q) { return !isNaN(q); }

message("Implementing 'equal'...");

function equal(a,b) {
	if (ispair(a) && ispair(b)) {
		return (equal(car(a),car(b)) && equal(cdr(a),cdr(b)));
	} else {
		if (isnumber(a) && isnumber(b)) {
			return (a==b);
		} else {
			if (issymbol(a) && issymbol(b)) {
				return symbolequal(a,b);
			} else {
				return (a==b);  // takes care of strings and nulls
			}
		}
	}
}

message("Implementing 'assoc'...");

function assoc(key,alist) {
	if (alist==null) {
		return false;
	} else {
		var item=car(alist);
		if (equal(key,car(item))) {
			return item;
		} else {
			return assoc(key,cdr(alist));
		}
	}
}

message("Implementing 'map'...");

function map(proc,x) {
	if (x==null) { return null; } else { return cons(proc(car(x)),map(proc,cdr(x))); }
}

////////////////////////// econoscheme starts here:
message("<br><b>Initializing Econo-Scheme</b><br>");
message("<pre>\n;;; A metacircular evaluator for Scheme.\n;;;\n;;; This program is a simple Scheme evaluator, written in Scheme. \n;;;\n;;; <b>Copyright (C) Vincent Manis, 1991. </b>\n;;;\n;;; Cosmetic changes by Carl Alphonce, June 1992.\n;;;\n;;; Code added by Johnny Kam and polished by Carl Alphonce, June 1992. \n;;;\n;;; assq->assv by Jim Little, March 1993.\n;;; find-binding a semi-predicate now  Jim Little, March 1993.\n;;;\n;;; Cosmetic changes, moduleized, macros changed, and user interface revised,\n;;; Vincent Manis, 1993 November. \n;;;\n;;; Harmonized with text (cosmetically).  J. Little 1995 June</pre>");
message("<b>Ported over to JavaScript 1.2 by Joseph Wong, January 1998.</b><br>");

unbound=quote("**unbound**");

undefined=quote("**undefined**");

voidval=quote("**voidval**");

procedureflag=quote("**procedure**");

function makeprocedure(args,body,env) {
	return list(procedureflag,args,body,env);
}

function isprocedure(proc) {
	if (ispair(proc)) { return equal(car(proc),procedureflag); } else { return false; }
}

function procedureparams(proc) {
	if (isprocedure(proc)) {
		return listref(proc,1);
	} else {
		evaluatorerror("Procedure expected",proc);
		return undefined;
	}
}

function procedurebody(proc) {
	if (isprocedure(proc)) {
		return listref(proc,2);
	} else {
		evaluatorerror("Procedure expected",proc);
		return undefined;
	}
}

function procedureenv(proc) {
	if (isprocedure(proc)) {
		return listref(proc,3);
	} else {
		evaluatorerror("Procedure expected",proc);
		return undefined;
	}
}

function extendenvironment(names,values,env) {

function newframe(n,v) {
	if ((n==null) && (v==null))
		{ return null; }
	else if (n==null)
		{ evaluatorerror("Too many arguments",cons(names,values)); return undefined; }
	else if (v==null)
		{ evaluatorerror("Too few arguments",cons(names,values)); return undefined; }
	else if (ispair(n) && issymbol(car(n)))
		{ return cons(cons(car(n),car(v)),newframe(cdr(n),cdr(v))); }
	else
		{ evaluatorerror("Invalid argument list",names); return undefined; }
}

	return cons(newframe(names,values),env);
}

function findbinding(symb,env) {
	if (env==null) {
		return false;
	} else {
		var x=assoc(symb,car(env));
		if (!x) {
			return findbinding(symb,cdr(env));
		} else {
			return x;
		}
	}
}

function getbinding(symb,env) {
	var x=findbinding(symb,env);
	if (!x) {
		evaluatorerror("Unbound variable (get)",symb);
		return undefined;
	} else {
		return cdr(x);
	}
}

function setbinding(symb,val,env) {
	var x=findbinding(symb,env);
	if (!x) {
		evaluatorerror("Unbound variable (set)",symb);
	} else {
		setcdr(x,val);
	}
}

function setbindingcar(symb,val,env) {
//	var x=findbinding(symb,env);
//	if (!x) {
//		evaluatorerror("Unbound variable (set-car!)",symb);
//	} else {
//		ispair(cdr(x)) ? setcar(cdr(x),val) : evaluatorerror("Variable is not a pair (set-car!)",symb);
//	}

	var x=selfeval(symb,env)
	ispair(x) ? setcar(x,val) : evaluatorerror("Variable is not a pair (set-car!)",symb);
}

function setbindingcdr(symb,val,env) {
//	var x=findbinding(symb,env);
//	if (!x) {
//		evaluatorerror("Unbound variable (set-cdr!)",symb);
//	} else {
//		ispair(cdr(x)) ? setcdr(cdr(x),val) : evaluatorerror("Variable is not a pair (set-car!)",symb);
//	}

	var x=selfeval(symb,env)
	ispair(x) ? setcdr(x,val) : evaluatorerror("Variable is not a pair (set-cdr!)",symb);
}

function defbinding(symb,val,env) {
	var x=assoc(symb,car(env));
	if (!x) {
		setcar(env,cons(cons(symb,val),car(env)));
	} else {
		setcdr(x,val);
	}
}

function getarg(exp,n) {
	return car(getrest(exp,n));
}

function getrest(exp,n) {

function find(x,m) {
	if (ispair(x)) {
		if (m==0) {
			return x;
		} else {
			return find(cdr(x),m-1);
		}
	} else {
		evaluatorerror("Invalid expression",exp);
		return undefined;
	}
}

return find(exp,n);
}

function selfsequence(exp,env) {

function seq(val,exp,env) {
	if (exp==null) {
		return val;
	} else {
		return seq(selfeval(car(exp),env),cdr(exp),env);
	}
}

return seq(unbound,exp,env);
}

specialforms=null;

function definespecial(symb,proc) {
	message("Defining special form: "+symboltostring(symb));
	var x=assoc(symb,specialforms);
	if (x) {
		setcdr(x,proc)
	} else {
		specialforms=cons(cons(symb,proc),specialforms);
	}
}

function definespecialforms() {
	definespecial(quote("quote"),new Function("exp","env","return getarg(exp,1);"));
	definespecial(quote("lambda"),new Function("exp","env","return makeprocedure(getarg(exp,1),getrest(exp,2),env);"));
	definespecial(quote("set!"),new Function("exp","env","setbinding(getarg(exp,1),selfeval(getarg(exp,2),env),env); return voidval;"));
	definespecial(quote("if"),new Function("exp","env","return selfeval(getarg(exp,1),env) ? selfeval(getarg(exp,2),env) : selfeval(getarg(exp,3),env);"));
	definespecial(quote("begin"),new Function("exp","env","return selfsequence(getrest(exp,1),env);"));
	definespecial(quote("define"),new Function("exp","env","defbinding(getarg(exp,1),selfeval(getarg(exp,2),env),env); return voidval;"));
	definespecial(quote("define-macro"),new Function("exp","env","defmacro(getarg(exp,1),selfeval(getarg(exp,2),env)); return voidval;"));

	definespecial(quote("let"),new Function("exp","env","return selfsequence(getrest(exp,2),extendenvironment(map(car,getarg(exp,1)),map(new Function('x','return selfeval(car(cdr(x)),env);'),getarg(exp,1)),env))"));

	definespecial(quote("set-car!"),new Function("exp","env","setbindingcar(getarg(exp,1),selfeval(getarg(exp,2),env),env); return voidval;"));
	definespecial(quote("set-cdr!"),new Function("exp","env","setbindingcdr(getarg(exp,1),selfeval(getarg(exp,2),env),env); return voidval;"));
}

function defmacro(macname,expander) {
	definespecial(macname,new Function("exp","env","return selfeval(selfsequence(procedurebody(expander),extendenvironment(procedureparams(expander),list(exp),procedureenv(expander))),env);"));
}

function selfeval(exp,env) {
	return simpleform(exp,env);
}

function isconstant(exp) {
	return (isnumber(exp) || isboolean(exp) || isstring(exp));
}

function simpleform(exp,env) {
	if (isconstant(exp))
		{ return exp; }
	else if (issymbol(exp))
		{ return getbinding(exp,env); }
	else if (ispair(exp))
		{	var b=assoc(car(exp),specialforms);
			return (( b ? cdr(b) : selfapplication )(exp,env)); }
	else { evaluatorerror("Incorrect expression",exp); return undefined; }
}

function selfapplication(exp,env) {
	function evalarg(arg) { return selfeval(arg,env); }
	var evaluatedargs=map(evalarg,exp);
	var operator=car(evaluatedargs);
	var operands=cdr(evaluatedargs);

	if (isprimitive(operator))
		{ return ((primitiveprocedure(operator))(operands)); }
	else if (isprocedure(operator))
		{ return selfsequence(procedurebody(operator),extendenvironment(procedureparams(operator),operands,procedureenv(operator))); }
	else { evaluatorerror("Procedure required",exp); return undefined; }
}

function isprimitive(x) {
	return (typeof(x)=="function");
}

function primitiveprocedure(x) {
	return x;
}

function makeprimitiveenvironment() {
	var pf=extendenvironment(null,null,null);
	function def(name,proc) { message("Defining primitive: "+symboltostring(name)); defbinding(name,proc,pf); }

	def(quote("+"),new Function("x","return ( car(x) + car(cdr(x)));"));
	def(quote("-"),new Function("x","return ( car(x) - car(cdr(x)));"));
	def(quote("*"),new Function("x","return ( car(x) * car(cdr(x)));"));
	def(quote("/"),new Function("x","return ( car(x) / car(cdr(x)));"));
	def(quote("<"),new Function("x","return ( car(x) < car(cdr(x)));"));
	def(quote("="),new Function("x","return ( car(x) == car(cdr(x)));"));
	def(quote(">"),new Function("x","return ( car(x) > car(cdr(x)));"));
	def(quote("<="),new Function("x","return ( car(x) <= car(cdr(x)));"));
	def(quote(">="),new Function("x","return ( car(x) >= car(cdr(x)));"));

	def(quote("car"),new Function("x","return car( car(x) );"));
	def(quote("cdr"),new Function("x","return cdr( car(x) );"));
	def(quote("null?"),new Function("x","return ( car(x) == null );"));
	def(quote("not"),new Function("x","return !car(x);"));
	def(quote("equal?"),new Function("x","return equal( car(x), car(cdr(x)) );"));
	def(quote("cons"),new Function("x","return cons( car(x), car(cdr(x)) );"));

	def(quote("display"),new Function("x","display( car(x) ); return voidval;"));
	def(quote("newline"),new Function("x","top.frames[1].document.writeln('<BR>'); return voidval;"));

	def(quote("#t"),true);
	def(quote("#f"),false);

	def(quote("native"),new Function("x","return eval( car(x) );"));

	return pf;
}

function evaluatorerror(what,irritant) {
	top.frames[1].document.writeln("<BR>Error in self-eval: ",what);
	if (!equal(voidval,irritant)) { show(irritant); };
	top.frames[1].document.writeln("<BR>...resetting to top level.<BR>");
	toplevel();
}

function show(arg) {

function show1(y) {
	top.frames[1].document.writeln("(");
	show(car(y));
	show2(cdr(y));
}

function show2(z) {
	if (z==null)
		{ top.frames[1].document.writeln(")"); }
	else if (ispair(z)) {
		top.frames[1].document.writeln(spacechar);
		if (isprocedure(z)) {
			top.frames[1].document.writeln("<procedure>)");
		} else {
			show(car(z));
			show2(cdr(z));
		}
	} else {
		top.frames[1].document.writeln(" . ");
		show(z);
		top.frames[1].document.writeln(")");
	}
}

if (arg==null)
	{ top.frames[1].document.writeln("()"); }
else if (isboolean(arg))
	{ top.frames[1].document.writeln( arg ? "#t" : "#f" ); }
else if (ispair(arg)) {
	if (isprocedure(arg))
		{ top.frames[1].document.writeln("<procedure>"); }
	else  { show1(arg); } }
else if (issymbol(arg)) { top.frames[1].document.writeln(cdr(arg)); }
else if (typeof(arg)=="string")
		{ top.frames[1].document.writeln('"',arg,'"'); } else { top.frames[1].document.writeln(arg); }

}

function display(what)
{
	show(what);
	top.frames[1].document.writeln("<BR>");
}

function toplevel() {}

/////////////////// initialization code below:

message("Initializing special forms...");
top.frames[1].scrollBy(0,10000);

definespecialforms();

message("");
message("Initializing primitive environment...");
top.frames[1].scrollBy(0,10000);

env=makeprimitiveenvironment();

courier=false;

message("");
message("Initializing repl...");
top.frames[1].scrollBy(0,10000);

function repl() {
 	if (!courier) { top.frames[1].document.writeln("<font face='courier new'>"); courier=true; }
	exp=top.frames[2].document.forms[0].elements[0].value;
	if (exp!="") {
		top.frames[1].document.writeln("jscm>&nbsp;",exp,"<BR>");
		var quoted=quote(exp);
		var answer=selfeval(quoted,env);
		if (!equal(answer,voidval)) {
			top.frames[1].document.writeln("&nbsp;&nbsp;&nbsp;=>");
			display(answer); }
}}

message("<font size=+2>jScheme is now running.</font><br>");
top.frames[1].scrollBy(0,10000);

</script>
</html>