implement MathCalc; include "sys.m";	sys: Sys; include "draw.m"; include "tk.m";	tk: Tk; include "bufio.m";	bufmod : Bufio;Iobuf : import bufmod; include "../lib/tcl.m"; include "tcllib.m";  MathCalc : module {	init: fn(nil: ref Draw->Context, nil: list of string);}; CALCPATH: con "/dis/lib/tcl_calc.dis"; init(nil: ref Draw->Context, nil: list of string){	sys = load Sys Sys->PATH;	cal := load TclLib CALCPATH;	if (cal==nil){		sys->print("mathcalc: can't load %s: %r\n", CALCPATH);		exit;	}	bufmod = load Bufio Bufio->PATH;	if (bufmod==nil){		sys->print("bufmod load %r\n");		exit;	}	iob := bufmod->fopen(sys->fildes(0),bufmod->OREAD);	if (iob==nil){		sys->print("mathcalc: cannot open stdin for reading: %r\n");		return;	}	input : string;	new_inp := "calc%";	sys->print("%s ", new_inp);	while((input=iob.gets('\n'))!=nil){		input=input[0:len input -1];		if (input=="quit")			exit;		arr:=array[] of {input};		(i,msg):=cal->exec(nil,arr);		if (msg!=nil)			sys->print("%s\n",msg);		sys->print("%s ", new_inp);	}	}  # expr0 : expr1#	| expr0 '+' expr0#	| expr0 '-' expr0#	;## expr1 : expr2#	| expr1 '*' expr1#	| expr1 '/' expr1#	;## expr2 : '-' expr2#	| '+' expr2#	| expr3#	;## expr3 : INT#	| REAL#	;