table of contents
| GRAP(1) | General Commands Manual | GRAP(1) |
NAME¶
grap — Kernighan
and Bentley's language for typesetting graphs
SYNOPSIS¶
grap |
[-d defines_file]
[-D] [-l]
[-M include path]
[-R] [-r]
[-v] [-u]
[-C] [-c]
[-h] [filename ...] |
DESCRIPTION¶
grap is an implementation of Kernighan and
Bentley's language for typesetting graphs, as described in ``Grap-A Language
for Typesetting Graphs, Tutorial and User Manual,'' by Jon L. Bentley and
Brian W. Kernighan, revised May 1991, which is the primary source for
information on how to use grap. As of this writing,
it is available electronically at
http://www.kohala.com/start/troff/cstr114.ps.
Additional documentation and examples, packaged with
grap, may have been installed locally as well. If
available, paths to them can be displayed using grap
-h or grap
-v (or grap
--help / grap
--version)
This version is a black box implementation of
grap, and some inconsistencies are to be expected.
The remainder of this manual page will briefly outline the
grap language as implemented here.
grap is a pic(1)
pre-processor. It takes commands embedded in a troff(1)
source file which are surrounded by .G1 and
.G2 macros, and rewrites them into
pic commands to display the graph. Other lines are copied.
Output is always to the standard output, which is usually redirected. Input
is from the given filenames,
which are read in order. A filename of
- is the standard input. If no
filenames are given, input is
read from the standard input.
Because grap is a pic
preprocessor, and GNU pic will output TeX, it is possible
to use grap with TeX.
The -d option specifies a file of macro
definitions to be read at startup, and defaults to
/usr/share/grap/grap.defines . The -D option
inhibits the reading of any initial macros file (the
-l flag is a synonym for -D,
though I do not remember why). The defines file can also be given using the
GRAP_DEFINES environment variable. (See below).
-v prints the version information on the
standard output and exits. --version is a synonym
for -v.
-u makes labels unaligned by default. This
version of grap uses new features of GNU
pic to align the left and right labels with the axes, that
is that the left and right labels run at right angles to the text of the
paper. This may be useful in porting old grap
programs. -c makes plot strings unclipped by
default. Some versions of grap allow users to place
a string anywhere in the coordinate space, rather than only in the frame. By
default this version of grap does not plot any
string centered outside the frame. -c allows strings
to be placed anywhere. See also the clipped and
unclipped string modifiers described in the
plot statement.
-M is followed by a colon-separated list
of directories used to search for relative pathnames included via
copy. The path is also used to locate the defines
file, so if the -d changes the defines file name to
a relative name, it will be searched for in the path given by
-M. The search path always includes the current
directory, and by default that directory is searched last.
All numbers used internally by grap are
double precision floating point values. Sometimes using floating point
numbers has unintended consequences. To help avoid these problems,
grap can use two thresholds for comparison of
floating point numbers, set by -R or
-r. The -R flag sets coarse
comparison mode, which is suitable for most applications. If you are
plotting small values – less than 1e-6 or so – consider using
-r which uses very fine comparisons between numbers.
You may also want to rescale your plotted values to be larger in magnitude.
The coarse comarisons are used by default.
To be precise, the value by which two numbers must differ for
grap to consider them not equal is called the
comparison limit and the smallest non-zero number is called the minimum
value. The values a given version of grap uses for
these are included in the output of -v or
-h.
All grap commands are included between
.G1 and .G2 macros, which
are consumed by grap. The output contains
pic between .PS and
.PE macros. Any arguments to the
.G1 macro in the input are arguments to the
.PS macro in the output, so graphs can be scaled
just like pic diagrams. If -C is
given, any macro beginning with .G1 or .G2 is treated as a .G1 or .G2 macro,
for compatibility with old versions of troff. Using
-C also forces pure troff syntax on embedded font
change commands when strings have the size
attribute, and all strings to be unclipped.
The -h flag prints a brief help message
and exits. --help is a synonym for
-h.
It is possible for someone to cause grap
to fail by passing a bad format string and data to the
sprintf command. If grap is
integrated as part of the printing system, this could conceivably provided a
path to breaching security on the machine. If you choose to use
grap as part of a printing system run by the
super-user, you should disable sprintf commands.
This can be done by calling grap with the
-S flag, setting the
GRAP_SAFER environment variable, or compiling with
the GRAP_SAFER preprocessor symbol defined. (The GNU configure script
included with grap will define that preprocessor
symbol if the --with-grap-safe option is given.)
The grap commands are sketched below.
Refer to Kernighan and Bentley's paper for the details.
New versions of groff(1) will invoke
grap if -G is given.
Commands¶
Commands are separated from one another by newlines or semicolons (;).
frame
[line_description] [ht
height | wid width]
[[(top|bottom|left|
right) line_description]
...]
frame [ht
height | wid width]
[line_description]
[[(top|bottom|left|
right) line_description]
...]
dashed
0.5, or the literal solid. It
may also include a color keyword followed by the color
to draw the string in double quotes. Any color understood by the underlying
groff system can be used. Color can only be used under GNU pic, and is not
available in compatibility mode. Similarly, for pic implementations that
understand thickness, that attribute may be used with
a real valued parameter. Thickness is not available in
compatibility mode.
If the first line_description is given, the
frame is drawn with that style. The default is
solid. The height and width of the frame can also be
specified in inches. The default line style can be over-ridden for sides of
the frame by specifying additional parameters to
frame.
If no plotting commands have been given before the
frame command is issued, the frame will be output at
that point in the plotting stream relative to embedded
troff or pic commands. Otherwise the
frame is output before the first plotted object (even invisible ones).
ht and wid are in
inches by default, but can be any groff unit. If omitted,
the dimensions are 2 inches high by 3 inches wide.
coord [name]
[x expr,
expr] [y
expr, expr]
[log x |
log y | log
log]
coord command specifies
a new coordinate system or sets limits on the default system. It defines the
largest and smallest values that can be plotted, and therefore the scale of
the data in the frame. The limits for the x and y coordinate systems can be
given separately. If a name is given, that coordinate
system is defined, if not the default system is modified.
A coordinate system created by one coord
command may be modified by subsequent coord
commands. A grap program may declare a coordinate
space using coord, copy a
file of data through a macro that plots the data and finds its maxima and
minima, and then define the size of the coordinate system with a second
coord statement.
This command also determines if a scale is plotted
logarithmically. log log means the same thing as
log x log y.
draw [line_name]
[line_description]
[plot_string]
draw command defines
the style with which a given line will be plotted. If
line_name is given, the style is associated with that
name, otherwise the default style is set.
line_description is a pic line
description, and the optional plot_string is a string to
be centered at each point. The default line description is
invis, and the default plotting string is a centered
bullet, so by default each point is a filled circle, and they are unconnected.
If points are being connected, each draw command ends
any current line and begins a new one.
When defining a line style, that is the first
draw command for a given line name, specifying no
plot string means that there are to be no plot strings. Omitting the plot
string on subsequent draw commands addressing the
same named line means not to change the plot string. If a line has been
defined with a plot string, and the format is changed by a subsequent
draw statement, the plot string can be removed by
specifying "" in the draw statement.
The plot string can have its format changed through several
string_modifiers. String_modifiers are described in the description of the
plot command.
The standard defines file includes several macros useful as plot
strings, including bullet,
square, and delta.
new is a synonym for
draw.
next [line_name]
at [coordinates_name]
expr, expr
[line_description]
next command plots the
given point using the line style given by line_name, or
the default if none is given. If line_name is given, it
should have been defined by an earlier draw command,
if not a new line style with that name is created, initialized the same way as
the default style. The two expressions give the point's x and y values,
relative to the optional coordinate system. That system should have been
defined by an earlier coord command, if not, grap will
exit. If the optional line_description is given, it
overrides the style's default line description. You cannot over-ride the
plotting string. To use a different plotting string use the
plot command.
The coordinates may optionally be enclosed in parentheses: (expr, expr)
quoted_string
[string_modifiers] [,
quoted_string
[string_modifiers]] ... at
[coordinates_name] expr,
expr
plot expr
[format_string] at
[coordinates_name] expr,
expr
ljust, rjust,
above, and
below), and absolute and
relative size modifiers. See the pic
documentation for the description of the justification modifiers.
grap also supports the aligned
and unaligned modifiers which are briefly noted in the
description of the label command.
The standard defines file includes several macros useful as plot
strings, including bullet,
square, and delta.
Strings placed by either format of the
plot command are restricted to being within the
frame. This can be overridden by using the unclipped
attribute, which allows a string to be plotted in or out of the frame. The
-c and -C flags set
unclipped on all strings, and to prevent a string
from being plotted outside the frame when those flags are active, the
clipped attribute can be used to retore clipping
behavior. Though clipped or
unclipped can be applied to any string, it only has
meaning for plot statements.
size expr sets the
string size to expr points. If
expr is preceded by a + or -, the size is increased or
decreased by that many points.
If color and a color name in double quotes
appears, the string will be rendered in that color under a version of GNU
troff that supports color. Color is not available in compatibility mode.
In the second version, the expr is converted
to a string and placed on the graph. format_string is
a printf(3) format string. Only formatting escapes for
printing floating point numbers make sense. The format string is only
respected if the sprintf command is also active. See
the description of sprintf for the various ways to
disable it. Plot and sprintf
respond differently when grap is running safely.
Sprintf ignores any arguments, passing the format
string through without substitution. plot ignores
the format string completely, plotting expr using the
"%g" format.
Points are specified the same way as for
next commands, with the same consequences for
undefined coordinate systems.
The second form of this command is because the first form can be
used with a grap sprintf
expression (See Expressions).
ticks
(left|right|top|bottom)[
(in|out)
[expr]]
[on|auto
coord_name]
ticks
(left|right|top|bottom)
(in|out)
[expr] [up
expr |
down expr
| left
expr |
right expr]
at [coord_name]
expr [format_string] [[,
expr [format_string]]
...]
ticks
(left|right|top|bottom)
(in|out)
[expr] [up
expr |
down expr
| left
expr |
right expr]
from [coord_name] start_expr
to end_expr
[by [+|-|*|/]
by_expr] [format_string]
ticks
[left|right|top|bottom]
off
The first version of this command turns on the automatic tick
generation for a given side. The in or
out parameter controls the direction and length of
the ticks. If a coord_name is specified, the ticks are
automatically generated using that coordinate system. If no system is
specified, the default coordinate system is used. As with
next and plot, the
coordinate system must be declared before the ticks
statement that references it. This syntax for requesting automatically
generated ticks is an extension, and will not port to older
grap implementations.
The second version of the ticks command
overrides the automatic placement of the ticks by specifying a list of
coordinates at which to place the ticks. If the ticks are not defined with
respect to the default coordinate system, the
coord_name parameter must be given. For each tick a
printf(3) style format string can be given. The
format_string defaults to "%g". The format
string can also take string modifiers as described in the
plot command. To place ticks with no labels, specify
format_string as "".
If sprintf is disabled,
ticks behaves as plot with
respect to the format string.
The labels on the ticks may be shifted by specifying a direction
and the distance in inches to offset the label. That is the optional
direction and expression immediately preceding the
at.
The third format of the ticks command
over-rides the default tick generation with a set of ticks ar regular
intervals. The syntax is reminiscent of programming language for loops.
Ticks are placed starting at start_expr ending at
end_expr one unit apart. If the
by clause is specified, ticks are
by_expr units apart. If an operator appears before
by_expr each tick is operated on by that operator
instead of +. For example
ticks left out from 2 to 32 by *2
will put ticks at 2, 4, 8, 16, and 32. If format_string is specified, all ticks are formatted using it.
The parameters preceding the from act as
described above.
The at and for
forms of tick command may both be issued on the same side of a frame. For
example:
ticks left out from 2 to 32 by *2 ticks left in 3, 5, 7
will put ticks on the left side of the frame pointing out at 2, 4, 8, 16, and 32 and in at 3, 5, and 7.
The final form of ticks turns off ticks on
a given side. If no side is given the ticks for all sides are cancelled.
tick is a synonym for
ticks.
grid
(left|right|top|bottom)
[ticks off] [line_description]
[up expr
| down
expr |
left expr
| right
expr]
[on|auto
[coord_name]]
grid
(left|right|top|bottom)
[ticks off] [line_description]
[up expr
| down
expr |
left expr
| right
expr] at
[coord_name] expr
[format_string] [[, expr
[format_string]] ...]
grid
(left|right|top|bottom)
[ticks off] [line_description]
[up expr
| down
expr |
left expr
| right
expr] from [coord_name]
start_expr to
end_expr [by
[+|-|*|/] by_expr]
[format_string]
grid command is similar
to the ticks command except that
grid specifies the placement of lines in the frame.
The syntax is similar to ticks as well.
By specifying ticks off in the command, no
ticks are drawn on that side of the frame. If ticks appear on a side by
default, or have been declared by an earlier ticks
command, grid does not cancel them unless
ticks off is specified.
Instead of a direction for ticks, grid
allows the user to pick a line description for the grid lines. The usual
pic line descriptions are allowed.
Grids are labelled by default. To omit labels, specify the format string as "".
If sprintf is disabled,
grid behaves as plot with
respect to the format string.
label
(left|right|top|bottom)
quoted_string [string_modifiers]
[, quoted_string
[string_modifiers]] ... [up
expr |
down expr
| left
expr |
right expr]
label command places a
label on the given axis. It is possible to specify several labels, which will
be stacked over each other as in pic. The final argument, if
present, specifies how many inches the label is shifted from the axis.
By default the labels on the left and right labels run parallel to
the frame. You can cancel this by specifying
unaligned as a
string_modifier.
circle at
[coordinate_name] expr,
expr [radius
expr] [linedesc]
This command has been extended to take a line description, e.g.,
dotted. It also accepts the filling extensions
described below in the bar command. It will also
accept a color keyword that gives the color of the
outline of the circle in double quotes and a
fillcolor command that sets the color to fill the
circle with similarly. Colors are only available when compatibility mode is
off, and using a version of GNU pic that supports color.
line
[line_description] from
[coordinate_name] expr,
expr to
[coordinate_name] expr,
expr [line_description]
arrow
[line_description] from
[coordinate_name] expr,
expr to
[coordinate_name] expr,
expr [line_description]
solid. The line_description can
be given either before the from or after the
to clause. If both are given the second is used. It is
possible to specify one point in one coordinate system and one in another,
note that if both points are in a named coordinate system (even if they are in
the same named coordinate system), both points must have
coordinate_name given.copy
["filename"] [until
"string"] [thru
macro]
copy command imports
data from another file into the current graph. The form with only a filename
given is a simple file inclusion; the included file is simply read into the
input stream and can contain arbitrary grap commands.
The more common case is that it is a number list; see
Number Lists below.
The second form takes lines from the file, splits them into words delimited by one or more spaces, and calls the given macro with those words as parameters. The macro may either be defined here, or be a macro defined earlier. See Macros for more information on macros.
The filename may be omitted if the
until clause is present. If so the current file is
treated as the input file until string is encountered
at the beginning of the line.
copy is one of the workhorses of
grap. Check out the paper and
/usr/share/doc/grap/examples for more details.
Confirm the location of the examples directory using the
-v flag.
print (expr|string)
sh block
grap no macro
or variable expansion is done. I believe that this is also true for GNU
pic version 1.10. See the
Macros section for information on defining
blocks.pic
pic_statement
.PS and
.PE at the point where the command is issued.
Statements that begin with a period are considered to be
troff(statements) and are output in the enclosing
.PS and .PE at the point
where the command appears.
For the purposes of relative placement of pic or
troff commands, the frame is output immediately before the
first plotted object, or the frame statement, if
any. If the user specifies pic or troff
commands and neither any plotable object nor a frame
command, the commands will not be output.
graph Name
pic_commands
Frame. The
following places a second graph below the first:
graph Linear [ graph description ] graph Exponential with .Frame.n at \ Linear.Frame.s - (0, .05) [ graph description ]
name = expr
grap has only
numeric (double) variables.
Assignment creates a variable if it does not exist. Variables
persist across graphs. Assignments can cascade; a = b =
35 assigns 35 to a and
b.
bar
(up|right)
[coordinates_name] offset
ht height
[wid width]
[base base_offset]
[line_description]
bar
[coordinates_name] expr,
expr, [coordinates_name]
expr, expr,
[line_description]
bar command facilitates
drawing bar graphs. The first form of the command describes the bar somewhat
generally and has grap place it. The bar may extend up
or to the right, is centered on offset and extends up or
right height units (in the given coordinate system). For
example
bar up 3 ht 2
draws a 2 unit high bar sitting on the x axis, centered on x=3. By
default bars are 1 unit wide, but this can be changed with the
wid keyword. By default bars sit on the base axis,
i.e., bars directed up will extend from y=0. That may be overridden by the
base keyword. (The bar described above has corners
(2.5, 0) and (3.5, 2).)
The line description has been extended to include a
fill expr keyword that
specifies the shading inside the bar. Bars may be drawn in any line style.
They support the color and
fillcolor keywords described under
circle.
The second form of the command draws a box with the two points as corners. This can be used to draw boxes highlighting certain data as well as bar graphs. Note that filled bars will cover data drawn under them.
Control Flow¶
if expr
then block
[else block]
if statement provides
simple conditional execution. If expr is non-zero, the
block after the then statement
is executed. If not the block after the
else is executed, if present. See
Macros for the definition of blocks. Early
versions of this implementation of grap treated the
blocks as macros that were defined and expanded in place. This led to
unnecessary confusion because explicit separators were sometimes called for.
Now, grap inserts a separator (;) after the last
character in block, so constructs like
if (x == 3) { y = y + 1 }
x = x + 1
for block.for name
from from_expr
to to_expr
[by [+|-|*|/]
by_expr] do
block
ticks
command. The definition of block is discussed in
Macros. See also the note about implicit
separators in the description of the if command.
An = can be used in place of
from.
Expressions¶
grap supports most standard arithmetic
operators: + - / * ^. The carat (^) is exponentiation. In an
if statement grap also
supports the C logical operators ==, !=, &&, || and unary !. Also in
an if, == and != are overloaded for the comparison
of quoted strings. Parentheses are used for grouping.
Assignment is not allowed in an expression in any context, except
for simple cascading of assignments. a = b = 35
works as expected; a = 3.5 * (b = 10) does not
execute.
grap supports the following functions that
take one argument: log, exp,
int, sin,
cos, sqrt,
rand, floor,
ceil. The logarithms are base 10 and the
trigonometric functions are in radians. eexp returns
Euler's number to the given power and ln returns the
natural logarithm. The natural log, exponentiation functions and floor and
ceil are extensions and are probably not available in other
grap implementations.
rand returns a random number uniformly
distributed on [0,1). The following two-argument functions are supported:
atan2, min,
max. atan2 works just like
atan2(3). The random number generator can be seeded by
calling srand with a single parameter (converted
internally to an integer). Because its return value is of no use, you must
use srand as a separate statement, it is not part of
a valid expression. srand is not portable.
The getpid function takes no arguments and
returns the process id. This may be used to seed the random number
generator, but do not expect cryptographically random values to result.
Other than string comparison, no expressions can use strings. One
string valued function exists: sprintf
(format, [expr
[, expr]] ). It operates like
sprintf(3), except returning the value. It can be used
anywhere a quoted string is used. If grap is run
with -S, the environment variable
GRAP_SAFER is defined, or
grap has been compiled for safer operation, the
sprintf command will return the format string. This
mode of operation is only intended to be used only if
grap is being used as part of a super-user enabled
print system.
grap version 1.44 and beyond support two
functions for date and time manipulation, strptime
and strptime. strptime
parses a time using the strptime(3) function. It takes two
parameters, both strings, the format and a string to parse using that format
and returns a number that can be sorted directly - the number of seconds
since the UNIX epoch. strftime does the reverse. It
takes a string and a number and formats the number into a date. In both
functions, the format is the first parameter. The formats are defined in the
documentation for strftime(3).
Macros¶
grap has a simple but powerful macro
facility. Macros are defined using the define
command :
define name block
undefine name
define foo X coord x 1,3 X
foo appears in the text, it will be replaced
by coord x 1,3. Macros are literal, and can contain
newlines. If a macro does not span multiple lines, it should end in a
semicolon to avoid parsing errors.
Macros can take parameters, too. If a macro call is followed by a parenthesized, comma-separated list the values starting with $1 will be replaced in the macro with the elements of the list. A $ not followed by a digit is left unchanged. This parsing is very rudimentary; no nesting or parentheses or escaping of commas is allowed. Also, there is no way to say argument 1 followed by a digit (${1}0 in sh(1)).
The following will draw a line with slope 1.
define foo { next at $1, $2 }
for i from 1 to 5 { foo(i,i) }
undefine command
deletes a macro.
See the directory
/usr/share/doc/grap/examples for more examples of
macros. Confirm the location of the examples directory using the
-v flag.
Number Lists¶
A whitespace-separated list of numbers is treated specially. The
list is taken to be points to be plotted using the default line style on the
default coordinate system. If more than two numbers are given, the extra
numbers are taken to be additional y values to plot at the first x value.
Number lists in DWB grap can be comma-separated, and
this grap supports that as well. More precisely,
numbers in number lists can be separated by either whitespace, commas, or
both.
1 2 3 4 5 6
Will plot points using the default line style at (1,2), (1,3),(4,5) and (4,6). A simple way to plot a set of numbers in a file named ./data is:
.G1 copy "./data" .G2
Pic Macros¶
grap defines pic macros that can be used
in embedded pic code to place elements in the graph. The macros are
x_gg, y_gg, and
xy_gg. These macros define pic distances that
correspond to the given argument. They can be used to size boxes or to plot
pic constructs on the graph. To place a given construct on the graph, you
should add Frame.Origin to it. Other coordinate spaces can be used by
replacing gg with the name of the coordinate space.
A coordinate space named gg cannot be reliably
accessed by these macros.
The macros are emitted immediately before the frame is drawn.
DWB grap may use these as part of its
implementation. This grap provides them only for
compatibility. Note that these are very simple macros, and may not do what
you expect under complex conditions.
ENVIRONMENT VARIABLES¶
If the environment variable GRAP_DEFINES
is defined, grap will look for its defines file
there. If that value is a relative path name the path specified in the
-M option will be searched for it.
GRAP_DEFINES overrides the compiled in location of
the defines file, but may be overridden by the -d or
-D flags.
If GRAP_SAFER is set,
sprintf is disabled to prevent forcing
grap to core dump or smash the stack.
FILES¶
/usr/share/grap/grap.defines
SEE ALSO¶
atan2(3), groff(1), pic(1), printf(3), sh(1), sprintf(3), troff(1)
If documentation and examples have been installed,
grap --version or
grap --help will display the
locations.
BUGS¶
There are several small incompatibilities with K&R
grap. They include the sh
command not expanding variables and macros, and a more strict adherence to
parameter order in the internal commands.
Although much improved, the error reporting code can still be confused. Notably, an error in a macro is not detected until the macro is used, and it produces unusual output in the error message.
Iterating many times over a macro with no newlines can run
grap out of memory.
AUTHOR¶
This implementation was done by
Ted Faber ⟨faber@lunabase.org⟩.
Bruce Lilly ⟨bruce.lilly@gmail.com⟩
contributed many bug fixes, including a considerable revamp of the error
reporting code. If you can actually find an error in your
grap code, you can probably thank him.
grap was designed and specified by
Brian Kernighan and
Jon Bentley.
| March 11, 2006 | Debian |