implement Hist0; include "sys.m";	sys: Sys;	print: import sys;include "math.m";	math: Math;	fmin: import math; include "draw.m";include "tk.m";	tk: Tk; include "bufio.m";	bufio: Bufio;	Iobuf: import bufio; include "gr.m";	gr: GR;	Plot: import gr; Hist0: module{	init:	fn(nil: ref Draw->Context, argv: list of string);};  plotfile(ctxt: ref Draw->Context, nil: list of string, filename: string){	p := gr->open(ctxt,filename);	input := bufio->open(filename,bufio->OREAD);	if(input==nil){		print("can't read %s",filename);		exit;	} 	n := 0;	maxn := 100;	x := array[maxn] of real;	y := array[maxn] of real;	while(1){		xn := input.gett(" \t\n\r");		if(xn==nil)			break;		yn := input.gett(" \t\n\r");		if(yn==nil){			print("after reading %d pairs, saw singleton\n",n);			exit;		}		if(n>=maxn){			maxn *= 2;			newx := array[maxn] of real;			newy := array[maxn] of real;			for(i:=0; i<n; i++){				newx[i] = x[i];				newy[i] = y[i];			}			x = newx;			y = newy;		}		x[n] = real xn;		y[n] = real yn;		n++;	}	if(n==0){		print("empty input\n");		exit;	} 	for(i:=0; i<n; i++){		h := 0.2;		if(i==0) h *= x[i+1]-x[i];		else if(i==n-1) h *= x[i]-x[i-1];		else h *= fmin(x[i+1]-x[i],x[i]-x[i-1]);		barx := array[] of{x[i]-h,x[i]-h,x[i]+h,x[i]+h,x[i]-h};		bary := array[] of{0.,y[i],y[i],0.,0.};		p.graph(barx,bary);	}	p.paint("",nil,"",nil);	p.bye();} init(ctxt: ref Draw->Context, argv: list of string){	sys = load Sys Sys->PATH;	math = load Math Math->PATH;	tk = load Tk Tk->PATH;	bufio = load Bufio Bufio->PATH;	if((gr = load GR GR->PATH) == nil){		sys->print("%s: Can't load gr\n",hd argv);		exit;	} 	tkargs := "";	argv = tl argv;	if(argv != nil) {		tkargs = hd argv;		argv = tl argv;	}	if(argv!=nil)		plotfile(ctxt,argv,hd argv);}