%{## subject to the Lucent Public License 1.02#include "sys.m";	sys: Sys; include "draw.m"; include "bufio.m";	bufio: Bufio;	Iobuf: import bufio; include "math.m";	math: Math; include "arg.m"; Ndim: con 15;	# number of dimensionsNvar: con 203;	# hash table sizeMaxe: con 695.0;	# log of largest number Node: adt{	val:	real;	dim:	array of int;	# [Ndim] schar 	mk:	fn(v: real): Node;	text:	fn(n: self Node): string;	add:	fn(a: self Node, b: Node): Node;	sub:	fn(a: self Node, b: Node): Node;	mul:	fn(a: self Node, b: Node): Node;	div:	fn(a: self Node, b: Node): Node;	xpn:	fn(a: self Node, b: int): Node;	copy: fn(a: self Node): Node;};Var: adt{	name:	string;	node:	Node;};Prefix: adt{	val:	real;	pname:	string;}; digval := 0;fi: ref Iobuf;fund := array[Ndim] of ref Var;line: string;lineno := 0;linep := 0;nerrors := 0;peekrune := 0;retnode1: Node;retnode2: Node;retnode: Node;sym: string;vars := array[Nvar] of list of ref Var;vflag := 0; YYSTYPE: adt {	node:	Node;	var:	ref Var;	numb:	int;	val:	real;}; YYLEX: adt {	lval: YYSTYPE;	lex: fn(l: self ref YYLEX): int;	error: fn(l: self ref YYLEX, msg: string);};  %}%module Units{	init:	fn(nil: ref Draw->Context, args: list of string);} %type	<node>	prog expr expr0 expr1 expr2 expr3 expr4 %token	<val>	VAL%token	<var>	VAR%token	<numb>	SUP%%prog:	':' VAR expr	{		f := $2.node.dim[0];		$2.node = $3.copy();		$2.node.dim[0] = 1;		if(f)			yyerror(sys->sprint("redefinition of %s", $2.name));		else if(vflag)			sys->print("%s\t%s\n", $2.name, $2.node.text());	}|	':' VAR '#'	{		for(i:=1; i<Ndim; i++)			if(fund[i] == nil)				break;		if(i >= Ndim) {			yyerror("too many dimensions");			i = Ndim-1;		}		fund[i] = $2; 		f := $2.node.dim[0];		$2.node = Node.mk(1.0);		$2.node.dim[0] = 1;		$2.node.dim[i] = 1;		if(f)			yyerror(sys->sprint("redefinition of %s", $2.name));		else if(vflag)			sys->print("%s\t#\n", $2.name);	}|	'?' expr	{		retnode1 = $2.copy();	}|	'?'	{		retnode1 = Node.mk(1.0);	} expr:	expr4|	expr '+' expr4	{		$$ = $1.add($3);	}|	expr '-' expr4	{		$$ = $1.sub($3);	} expr4:	expr3|	expr4 '*' expr3	{		$$ = $1.mul($3);	}|	expr4 '/' expr3	{		$$ = $1.div($3);	} expr3:	expr2|	expr3 expr2	{		$$ = $1.mul($2);	} expr2:	expr1|	expr2 SUP	{		$$ = $1.xpn($2);	}|	expr2 '^' expr1	{		for(i:=1; i<Ndim; i++)			if($3.dim[i]) {				yyerror("exponent has units");				$$ = $1;				break;			}		if(i >= Ndim) {			i = int $3.val;			if(real i != $3.val)				yyerror("exponent not integral");			$$ = $1.xpn(i);		}	} expr1:	expr0|	expr1 '|' expr0	{		$$ = $1.div($3);	} expr0:	VAR	{		if($1.node.dim[0] == 0) {			yyerror(sys->sprint("undefined %s", $1.name));			$$ = Node.mk(1.0);		} else			$$ = $1.node.copy();	}|	VAL	{		$$ = Node.mk($1);	}|	'(' expr ')'	{		$$ = $2;	}%% init(nil: ref Draw->Context, args: list of string){	sys = load Sys Sys->PATH;	bufio = load Bufio Bufio->PATH;	math = load Math Math->PATH; 	arg := load Arg Arg->PATH;	arg->init(args);	arg->setusage("units [-v] [file]");	while((o := arg->opt()) != 0)		case o {		'v' => vflag = 1;		* => arg->usage();	}	args = arg->argv();	arg = nil; 	file := "/lib/units";	if(args != nil)		file = hd args;	fi = bufio->open(file, Sys->OREAD);	if(fi == nil) {		sys->fprint(sys->fildes(2), "units: cannot open %s: %r\n", file);		raise "fail:open";	}	lex := ref YYLEX; 	#	# read the 'units' file to	# develop a database	#	lineno = 0;	for(;;) {		lineno++;		if(readline())			break;		if(len line == 0 || line[0] == '/')			continue;		peekrune = ':';		yyparse(lex);	} 	#	# read the console to	# print ratio of pairs	#	fi = bufio->fopen(sys->fildes(0), Sys->OREAD);	lineno = 0;	for(;;) {		if(lineno & 1)			sys->print("you want: ");		else			sys->print("you have: ");		if(readline())			break;		peekrune = '?';		nerrors = 0;		yyparse(lex);		if(nerrors)			continue;		if(lineno & 1) {			isspcl: int;			(isspcl, retnode) = specialcase(retnode2, retnode1);			if(isspcl)				sys->print("\tis %s\n", retnode.text());			else {				retnode = retnode2.div(retnode1);				sys->print("\t* %s\n", retnode.text());				retnode = retnode1.div(retnode2);				sys->print("\t/ %s\n", retnode.text());			}		} else			retnode2 = retnode1.copy();		lineno++;	}	sys->print("\n");} YYLEX.lex(lex: self ref YYLEX): int{	c := peekrune;	peekrune = ' '; 	while(c == ' ' || c == '\t'){		if(linep >= len line)			return 0;	# -1?		c = line[linep++];	}	case c {	'0' to '9' or '.' =>		digval = c;		(lex.lval.val, peekrune) = readreal(gdigit, lex);		return VAL;	'×' =>		return '*';	'÷' =>		return '/';	'¹' or	'ⁱ' =>		lex.lval.numb = 1;		return SUP;	'²' or	'⁲' =>		lex.lval.numb = 2;		return SUP;	'³' or	'⁳' =>		lex.lval.numb = 3;		return SUP;	* =>		if(ralpha(c)){			sym = "";			for(i:=0;; i++) {				sym[i] = c;				if(linep >= len line){					c = ' ';					break;				}				c = line[linep++];				if(!ralpha(c))					break;			}			peekrune = c;			lex.lval.var = lookup(0);			return VAR;		}	}	return c;} ## all characters that have some# meaning. rest are usable as names#ralpha(c: int): int{	case c {	0 or	'+'  or	'-'  or	'*'  or	'/'  or	'['  or	']'  or	'('  or	')'  or	'^'  or	':'  or	'?'  or	' '  or	'\t'  or	'.'  or	'|'  or	'#'  or	'¹'  or	'ⁱ'  or	'²'  or	'⁲'  or	'³'  or	'⁳'  or	'×'  or	'÷'  =>		return 0;	}	return 1;} gdigit(nil: ref YYLEX): int{	c := digval;	if(c) {		digval = 0;		return c;	}	if(linep >= len line)		return 0;	return line[linep++];} YYLEX.error(lex: self ref YYLEX, s: string){	#	# hack to intercept message from yaccpar	#	if(s == "syntax error") {		lex.error(sys->sprint("syntax error, last name: %s", sym));		return;	}	sys->print("%d: %s\n\t%s\n", lineno, line, s);	nerrors++;	if(nerrors > 5) {		sys->print("too many errors\n");		raise "fail:errors";	}} yyerror(s: string){	l := ref YYLEX;	l.error(s);} Node.mk(v: real): Node{	return (v, array[Ndim] of {* => 0});} Node.add(a: self Node, b: Node): Node{	c := Node.mk(fadd(a.val, b.val));	for(i:=0; i<Ndim; i++) {		d := a.dim[i];		c.dim[i] = d;		if(d != b.dim[i])			yyerror("add must be like units");	}	return c;} Node.sub(a: self Node, b: Node): Node{	c := Node.mk(fadd(a.val, -b.val));	for(i:=0; i<Ndim; i++) {		d := a.dim[i];		c.dim[i] = d;		if(d != b.dim[i])			yyerror("sub must be like units");	}	return c;} Node.mul(a: self Node, b: Node): Node{	c := Node.mk(fmul(a.val, b.val));	for(i:=0; i<Ndim; i++)		c.dim[i] = a.dim[i] + b.dim[i];	return c;} Node.div(a: self Node, b: Node): Node{	c := Node.mk(fdiv(a.val, b.val));	for(i:=0; i<Ndim; i++)		c.dim[i] = a.dim[i] - b.dim[i];	return c;} Node.xpn(a: self Node, b: int): Node{	c := Node.mk(1.0);	if(b < 0) {		b = -b;		for(i:=0; i<b; i++)			c = c.div(a);	} else		for(i:=0; i<b; i++)			c = c.mul(a);	return c;} Node.copy(a: self Node): Node{	c := Node.mk(a.val);	c.dim[0:] = a.dim;	return c;} specialcase(a, b: Node): (int, Node){	c := Node.mk(0.0);	d1 := 0;	d2 := 0;	for(i:=1; i<Ndim; i++) {		d := a.dim[i];		if(d) {			if(d != 1 || d1)				return (0, c);			d1 = i;		}		d = b.dim[i];		if(d) {			if(d != 1 || d2)				return (0, c);			d2 = i;		}	}	if(d1 == 0 || d2 == 0)		return (0, c); 	if(fund[d1].name == "°C" &&	   fund[d2].name == "°F" &&	   b.val == 1.0) {		c = b.copy();		c.val = a.val * 9. / 5. + 32.;		return (1, c);	}

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