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To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
From: Pietro Gagliardi <pietro10@mac.com>
Date: Fri, 26 Oct 2007 18:38:24 -0400
Subject: [9fans] grap retarded??
Topicbox-Message-UUID: db13c110-ead2-11e9-9d60-3106f5b1d025

Hello.

I am writing a simple awk script powered by a shell script. It is  
called eg, which stands for equation grapher, and it graphs  
mathematical equations like on a graphing calculator. It works  
perfectly on Mac OS X (Google "grap" and you'll find an open-source  
version).

So I decided to send it to Plan 9 for testing, since Plan 9 already  
has grap. It doesn't work. What gives?

grap was giving me this funky error message saying that its "new"  
statement was followed by a newline, and that it didn't like that.  
The documentation allows "new" to have no arguments. Huh?

Here is some sample input:
.EG
y = x
.EE
.EG
# The letters x and y must each be one word for correct scanning
x < 2 * sin( y )
.EE
.EG
polar
r = sin( t / 180 )
.EE

== begin eg ==
# eg:  equation grapher
# by pietro gagliardi
# started october 24, 2007
# completed ?
# usage: eg files...
# produces grap output, so use as so:
#    eg file | grap | pic | troff

awk '
BEGIN {
	in_it = 0
	xmin = xmax = ymin = ymax = 0
	fwid = fht = lower = upper = step = 0
	showxaxis = showyaxis = showxticks = showyticks = 0
	showxlabel = showylabel = showgrid = 0
	complex = polar = start_drawing = i = 0
	pi    = "3.14159265358979323846264338327950288"
	negpi = "-" pi
	twopi = "6.28318530717958647692528676655900576"
# The value of 2*pi was calculated with GNU bc version 1.06
# running on Mac OS X 10.4.10 on a Core 2 Duo iMac. At the time,
# my C double type did not have the precision to get a value to
# check my hand-calculated values, so I used bc instead of PG hoc.
# I do not  know how it gets such values! One day I will find a
# machine where double can hold more than 15 digits. Thanks,
# scale variable of bc!
}

# .EG - begin graph
$1  == ".EG" || ($1 == "." && $2 == "EG") {
	in_it = 1
	set_defaults()
	printf ".G1"
	for (x = 2; x <= NF; x++)
		printf " %s", $x
	printf "\n"
	next
}

# .EE - end graph
# only counts while in graph
in_it && ($1 == ".EE" || ($1 == "." && $2 == "EG")) {
	finish_it()
	printf ".G2\n"
	in_it = 0
	next
}

# not in it - print
!in_it { print; next }

# From here on in, we assume we are in it

# # stuff - comment
$1 ~ /^\#/ { next }

# . followed by whatever is copied verbatim
$1 ~ /^\./ {
	start_drawing = 1
	code[i] = "literal"
	eqn[i] = $0
	i++
	next
}

# grap <stuff> - print verbatim, without grap
$1 == "grap" {
	start_drawing = 1
	s = ""
	for (x = 2; x <= NF; x++)
		s = s " " $x
	mode[i] = "literal"
	eqn[i] = s
	i++
	next
}

# pic <stuff> - print verbatim too (also sent to grap)
$1 == "pic" {
	start_drawing = 1
	mode[i] = "literal"
	eqn[i] = $0
	i++
	next
}

# frame <height> <width> - set frame size
$1 == "frame" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	fht  = $2
	fwid = $3
	next
}

# window <xmin> <xmax> <ymin> <ymin> - set coordinates
$1 == "window" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	xmin = lower = $2
	xmax = upper = $3
	ymin = lower = $4
	ymax = upper = $5
	next
}

# step (<lower> <upper>|[-]polar) [<step>] - control drawing
$1 == "step" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	if ($2 == "polar") {
		lower = 0
		upper = twopi
		if (NF > 2)
			step = $3
		else
			step = .01
	} else if ($2 == "-polar") {
		lower = negpi
		upper = pi
		if (NF > 2)
			step = $3
		else
			step = .01
	} else {
		lower = $2
		upper = $3
		if (NF >= 4)
			step = $4
		else
			step = .01
	}
	next
}

# grid (on|off) - control grid
$1 == "grid" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	showgrid = ($2 == "on") || (NF == 1)
	next
}

# axes ([xXyYrRtT]|on|off) - control axes
$1 == "axes" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	if (($2 == "on") || (NF == 1))
		showxaxis = showyaxis = showxlabel = showylabel = showxticks =  
showyticks = 1
	else if ($2 == "off")
		showxaxis = showyaxis = showxlabel = showylabel = showxticks =  
showyticks = 0
	else {
		showxaxis = showxlabel = showxticks = ($2 ~ /[xXrR]/)
		showyaxis = showylabel = showyticks = ($2 ~ /[yYtT]/)
	}
	next
}

# ticks ([xXyYrRtT]|on|off) - control ticks
$1 == "ticks" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	if (($2 == "on") || (NF == 1))
		showxticks = showyticks = 1
	else if ($2 == "off")
		showxticks = showyticks = 0
	else {
		showxticks = ($2 ~ /[xXrR]/)
		showyticks = ($2 ~ /[yYtT]/)
	}
	next
}

# axislabel ([xXyYrRtT]|on|off) - control labels on axes
$1 == "axislabel" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	if (($2 == "on") || (NF == 1))
		showxlabel = showylabel = 1
	else if ($2 == "off")
		showxlabel = showylabel = 0
	else {
		showxlabel = ($2 ~ /[xXrRtT]/)
		showylabel = ($2 ~ /[yYrRtT]/)
	}
	next
}

# rect - set rectangular coordinates
$1 == "rect" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	polar = 0
	next
}

# polar - set polar coordinates
$1 == "polar" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	polar = 1
	next
}

# real - set real coordinates
$1 == "real" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	complex = 0
	next
}

# complex - set complex coordinates
$1 == "complex" {
	if (start_drawing) {
		err("eg: control command cannot be used after draw")
		next
	}
	complex = 1
	next
}

# [xXyYrRtT] [(=|<|<=|>|>=)] equation - draw on given axis
$1 ~ /^[xXyYrRtT]$/ {
	start_drawing = 1
	mode[i] = tolower($1)
	s = ""
	start = 2
	if ($2 ~ /^(=|<|>|<=|>=)$/)
		start = 3
	for (x = start; x <= NF; x++)
		if (polar) {
			if ($x ~ /^[rR]$/)
				s = s " rcoord"
			else if ($x ~ /^[tT]$/)
				s = s " tcoord"
			else
				s = s " " $x
		} else {
			if ($x ~ /^[xXyY]$/)
				s = s " xpos"
			else
				s = s " " $x
		}
	eqn[i] = s
	if (start == 2)
		type[i] = "="
	else
		type[i] = $2
	i++
	next
}

# empty line or line with whitespace only - ignore
NF == 0 { next }

# else error
{ err("eg: bad line: " $0) }

END {
	if (in_it)
		err("eg: unclosed graph at end of file")
}

# set_defaults:  reset environment
function set_defaults() {
	xmin = ymin = lower = -10
	xmax = ymax = upper = 10
	fwid = fht = 4
	complex = i = 0
	showxaxis = showyaxis = showxticks = showyticks = showxlabel =  
showylabel = showgrid = 1
	step = .01
}

# finish_it:  draw the graph
function finish_it() {
	printf "xmin = %s\n", xmin
	printf "xmax = %s\n", xmax
	printf "ymin = %s\n", ymin
	printf "ymax = %s\n", ymax
	printf "frame invis ht %s wid %s\n", fht, fwid
	printf "coord x xmin,xmax y ymin,ymax\n"
	if (showgrid) {
		printf "grid bot  ticks off from xmin to xmax by 1\n"
		printf "grid left ticks off from ymin to ymax by 1\n"
	}
	if (showxaxis) {
		printf "arrow solid from xmin,0 to xmax,0\n"
		printf "arrow solid from xmax,0 to xmin,0\n"
	}
	if (showyaxis) {
		printf "arrow solid from 0,ymin to 0,ymax\n"
		printf "arrow solid from 0,ymax to 0,ymin\n"
	}
	if (showxlabel) {
		xstr = "x"
		if (polar)
			xstr = "r"
		printf "\" \\fI%s\\fP\" ljust at xmax,0\n", xstr
	}
	if (showylabel) {
		ystr = "y"
		if (polar)
			ystr = "\\(*h"
		if (complex)
			ystr = ystr "i"
		printf "\"\\fI%s\\fP\"  above at 0,ymax\n", ystr
	}
	if (showxticks) {
		printf "for xticks from (xmin + 1) to (xmax - 1) by 1 do {\n"
		printf "if xticks != 0 then {\n"
		printf "line solid from xticks,0 to xticks,.25\n"
		printf "sprintf(\"%%g\", xticks) above at xticks,.25\n"
		printf "}\n"
		printf "}\n"
	}
	if (showyticks) {
		printf "for yticks from (ymin + 1) to (ymax - 1) by 1 do {\n"
		printf "if yticks != 0 then {\n"
		printf "line solid from 0,yticks to .25,yticks\n"
		printf "sprintf(\" %%g\",  yticks) ljust at .25,yticks\n"
		printf "}\n"
		printf "}\n"
	}
	for (x = 0; x < i; x++) {
		if (mode[x] == "literal")
			printf "%s\n", eqn[x]
		else {
			if (type[x] ~ /=/)
				drawmode = "solid"
			else
				drawmode = "dashed"
			printf "new\ndraw %s\n", drawmode
			printf "for xpos from %s to %s by %s do {\n", lower, upper, step
			if (!polar) {
				if (mode[x] == "y") {
					printf "next at xpos, (%s)\n", eqn[x]
					if (type[x] ~ /</)
						printf "line from (xpos, (%s)) to (xpos, ymin)\n", eqn[x]
					else if (type[x] ~ />/)
						printf "line from (xpos, (%s)) to (xpos, ymax)\n", eqn[x]
				} else
					printf "next at (%s), xpos\n", eqn[x]
			} else {
				if (mode[x] == "r")
					printf "tcoord = xpos\nrcoord = %s\n", eqn[x]
				else
					printf "rcoord = xpos\ntcoord = %s\n", eqn[x]
				printf "xpoint = rcoord * cos(tcoord)\n"
				printf "ypoint = rcoord * sin(tcoord)\n"
				printf "next at xpoint, ypoint\n"
			}
			printf "}\n"
		}
	}
}

# err:  print error
function err(s) {
	print s | "cat 1>&2"
}

' $*
== end of eg ==

I could attach it if necessary.