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<h2>21. PIC Reference
<a name="21. PIC Reference"></a>
</h2>
<p style="margin-top: 1em"><font color="#000000">This is an
annotated grammar of <b>pic</b>.</font></p>
<h3>21.1. Lexical Items
<a name="21.1. Lexical Items"></a>
</h3>
<p style="margin-top: 1em"><font color="#000000">In
general, <b>pic</b> is a free-format, token-oriented
language that ignores whitespace outside strings. But
certain lines and contructs are specially interpreted at the
lexical level:</font></p>
<p style="margin-top: 1em"><font color="#000000">A comment
begins with <b>#</b> and continues to <b>\n</b> (comments
may also follow text in a line). A line beginning with a
period or backslash may be interpreted as text to be passed
through to the post-processor, depending on command-line
options. An end-of-line backslash is interpreted as a
request to continue the line; the backslash and following
newline are ignored.</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000">Here
are the grammar terminals:</font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="10%"></td>
<td width="6%">
<p style="margin-top: 1em"><font color="#000000"><small>INT</small></font></p> </td>
<td width="4%"></td>
<td width="38%">
<p style="margin-top: 1em"><font color="#000000">A positive
integer.</font></p> </td>
<td width="42%">
</td></tr>
</table>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><small>NUMBER</small></font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="10%"></td>
<td width="8%"></td>
<td width="2%"></td>
<td width="80%">
<p><font color="#000000">A floating point numeric constant.
May contain a decimal point or be expressed in scientific
notation in the style of <i>printf</i>(3)’s %e escape.
A trailing ‘i’ or ‘I’ (indicating
the unit ‘inch’) is ignored.</font></p></td></tr>
<tr valign="top" align="left">
<td width="10%"></td>
<td width="8%">
<p style="margin-top: 1em"><font color="#000000"><small>TEXT</small></font></p> </td>
<td width="2%"></td>
<td width="80%">
<p style="margin-top: 1em"><font color="#000000">A string
enclosed in double quotes. A double quote within
<small>TEXT</small> must be preceded by a backslash. Instead
of <small>TEXT</small> you can use</font></p></td></tr>
</table>
<p style="margin-left:30%; margin-top: 1em"><font color="#000000">sprintf
( TEXT [, <expr> ...] )</font></p>
<p style="margin-left:20%; margin-top: 1em"><font color="#000000">except
after the ‘until’ and ‘last’
keywords, and after all ordinal keywords (‘th’
and friends).</font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="10%"></td>
<td width="16%">
<p style="margin-top: 1em"><font color="#000000"><small>VARIABLE</small></font></p> </td>
<td width="74%">
</td></tr>
</table>
<p style="margin-left:20%;"><font color="#000000">A string
starting with a character from the set [a-z], optionally
followed by one or more characters of the set [a-zA-Z0-9_].
(Values of variables are preserved across
pictures.)</font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="10%"></td>
<td width="10%">
<p style="margin-top: 1em"><font color="#000000"><small>LABEL</small></font></p> </td>
<td width="80%">
<p style="margin-top: 1em"><font color="#000000">A string
starting with a character from the set [A-Z], optionally
followed by one or more characters of the set
[a-zA-Z0-9_].</font></p> </td></tr>
</table>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><small>COMMAND-LINE</small></font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="20%"></td>
<td width="80%">
<p><font color="#000000">A line starting with a command
character (‘.’ in groff mode, ‘\’ in
TeX mode).</font></p></td></tr>
</table>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><small>BALANCED-TEXT</small></font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="20%"></td>
<td width="80%">
<p><font color="#000000">A string either enclosed by
‘{’ and ‘}’ or with <i>X</i> and
<i>X</i>, where <i>X</i> doesn’t occur in the
string.</font></p> </td></tr>
</table>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><small>BALANCED-BODY</small></font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="20%"></td>
<td width="80%">
<p><font color="#000000">Delimiters as in
<small>BALANCED-TEXT</small> ; the body is interpreted as
‘<b>⟨ command⟩ ...</b>’.</font></p></td></tr>
</table>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><small>FILENAME</small></font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="20%"></td>
<td width="80%">
<p><font color="#000000">The name of a file. This has the
same semantics as <small>TEXT</small> .</font></p></td></tr>
</table>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><small>MACRONAME</small></font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="20%"></td>
<td width="50%">
<p><font color="#000000">Either <small>VARIABLE</small> or
<small>LABEL</small> .</font></p></td>
<td width="30%">
</td></tr>
</table>
<h3>21.2. Semi-Formal Grammar
<a name="21.2. Semi-Formal Grammar"></a>
</h3>
<p style="margin-top: 1em"><font color="#000000">Tokens not
enclosed in ⟨ ⟩ are literals, except:</font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="4%">
<p style="margin-top: 1em"><font color="#000000">1.</font></p> </td>
<td width="6%"></td>
<td width="90%">
<p style="margin-top: 1em"><font color="#000000"><b>\n</b>
is a newline.</font></p></td></tr>
<tr valign="top" align="left">
<td width="4%">
<p style="margin-top: 1em"><font color="#000000">2.</font></p> </td>
<td width="6%"></td>
<td width="90%">
<p style="margin-top: 1em"><font color="#000000">Three dots
is a suffix meaning ‘replace with 0 or more
repetitions of the preceding element(s).</font></p></td></tr>
<tr valign="top" align="left">
<td width="4%">
<p style="margin-top: 1em"><font color="#000000">3.</font></p> </td>
<td width="6%"></td>
<td width="90%">
<p style="margin-top: 1em"><font color="#000000">An
enclosure in square brackets has its usual meaning of
‘this clause is optional’.</font></p></td></tr>
<tr valign="top" align="left">
<td width="4%">
<p style="margin-top: 1em"><font color="#000000">4.</font></p> </td>
<td width="6%"></td>
<td width="90%">
<p style="margin-top: 1em"><font color="#000000">Square-bracket-enclosed
portions within tokens are optional. Thus,
‘h[eigh]t’ matches either ‘height’
or ‘ht’.</font></p></td></tr>
</table>
<p style="margin-top: 1em"><font color="#000000">If one of
these special tokens has to be referred to literally, it is
surrounded with single quotes.</font></p>
<p style="margin-top: 1em"><font color="#000000">The
top-level <b>pic</b> object is a picture.</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><picture>
::= <br>
.PS [NUMBER [NUMBER]]\n <br>
<statement> ... <br>
.PE \n</font></p>
<p style="margin-top: 1em"><font color="#000000">The
arguments, if present, represent the width and height of the
picture, causing <b>pic</b> to attempt to scale it to the
given dimensions in inches. In no case, however, the X and
Y dimensions of the picture exceed the values of the
style variables <b>maxpswid</b> and <b>maxpsheight</b>
(which default to the normal 8.5i by 11i page
size).</font></p>
<p style="margin-top: 1em"><font color="#000000">If the
ending ‘.PE’ is replaced by ‘.PF’,
the page vertical position is restored to its value at the
time ‘.PS’ was encountered. Another alternate
form of invocation is ‘.PS <
<small>FILENAME</small> ’, which replaces the
‘.PS’ line with a file to be interpreted by
<b>pic</b> (but this feature is deprecated).</font></p>
<p style="margin-top: 1em"><font color="#000000">The
‘.PS’, ‘.PE’, and ‘.PF’
macros to perform centering and scaling are normally
supplied by the post-processor.</font></p>
<p style="margin-top: 1em"><font color="#000000">In the
following, either ‘|’ or a new line starts an
alternative.</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><statement>
::= <br>
<command> ; <br>
<command> \n</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><command>
::= <br>
<primitive> [<attribute>] <br>
LABEL : [;] <command> <br>
LABEL : [;] <command> [<position>] <br>
{ <command> ... } <br>
VARIABLE [:] = <any-expr> <br>
figname = MACRONAME <br>
up | down | left | right <br>
COMMAND-LINE <br>
command <print-arg> ... <br>
print <print-arg> ... <br>
sh BALANCED-TEXT <br>
copy FILENAME <br>
copy [FILENAME] thru MACRONAME [until TEXT] <br>
copy [FILENAME] thru BALANCED-BODY [until TEXT] <br>
for VARIABLE = <expr> to <expr> [by [*]
<expr>] do BALANCED-BODY <br>
if <any-expr> then BALANCED-BODY [else BALANCED-BODY]
<br>
reset [VARIABLE [[,] VARIABLE ...]]</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><print-arg>
::= <br>
TEXT <br>
<expr> <br>
<position></font></p>
<p style="margin-top: 1em"><font color="#000000">The
current position and direction are saved on entry to a
‘{ ... }’ construction and restored on
exit from it.</font></p>
<p style="margin-top: 1em"><font color="#000000">Note that
in ‘if’ constructions, newlines can only occur
in <small>BALANCED-BODY</small> . This means that</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000">if
<br>
{ ... } <br>
else <br>
{ ... }</font></p>
<p style="margin-top: 1em"><font color="#000000">fails. You
have to use the braces on the same line as the
keywords:</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000">if
{ <br>
... <br>
} else { <br>
... <br>
}</font></p>
<p style="margin-top: 1em"><font color="#000000">This
restriction doesn’t hold for the body after the
‘do’ in a ‘for’
construction.</font></p>
<p style="margin-top: 1em"><font color="#000000">At the
beginning of each picture, ‘figname’ is reset to
the vbox name ‘graph’; this command has only a
meaning in TeX mode. While the grammar rules allow digits
and the underscore in the value of ‘figname’,
TeX normally accepts uppercase and lowercase letters only as
box names (you have to use ‘\csname’ if you
really need to circumvent this limitation).</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><any-expr>
::= <br>
<expr> <br>
<text-expr> <br>
<any-expr> <logical-op> <any-expr> <br>
! <any-expr></font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><logical-op>
::= <br>
== | != | && | ’||’</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><text-expr>
::= <br>
TEXT == TEXT <br>
TEXT != TEXT</font></p>
<p style="margin-top: 1em"><font color="#000000">Logical
operators are handled specially by <b>pic</b> since they can
deal with text strings also. <b>pic</b> uses
<i>strcmp</i>(3) to test for equality of strings; an empty
string is considered as ‘false’ for
‘&&’ and ‘||’.</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><primitive>
::= <br>
box # closed object — rectangle <br>
circle # closed object — circle <br>
ellipse # closed object — ellipse <br>
arc # open object — quarter-circle <br>
line # open object — line <br>
arrow # open object — line with arrowhead <br>
spline # open object — spline curve <br>
move <br>
TEXT TEXT ... # text within invisible box <br>
plot <expr> TEXT # formatted text <br>
’[’ <command> ...
’]’</font></p>
<p style="margin-top: 1em"><font color="#000000">Drawn
objects within ‘[ ... ]’ are treated
as a single composite object with a rectangular shape (that
of the bounding box of all the elements). Variable and label
assignments within a block are local to the block. Current
direction of motion is restored to the value at start of
block upon exit. Position is <i>not</i> restored (unlike
‘{ }’); instead, the current position
becomes the exit position for the current direction on the
block’s bounding box.</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><attribute>
::= <br>
h[eigh]t <expr> # set height of closed figure <br>
wid[th] <expr> # set width of closed figure <br>
rad[ius] <expr> # set radius of circle/arc <br>
diam[eter] <expr> # set diameter of circle/arc <br>
up [<expr>] # move up <br>
down [<expr>] # move down <br>
left [<expr>] # move left <br>
right [<expr>] # move right <br>
from <position> # set from position of open figure
<br>
to <position> # set to position of open figure <br>
at <position> # set center of open figure <br>
with <path> # fix corner/named point at specified
location <br>
with <position> # fix position of object at specified
location <br>
by <expr-pair> # set object’s attachment point
<br>
then # sequential segment composition <br>
dotted [<expr>] # set dotted line style <br>
dashed [<expr>] # set dashed line style <br>
thick[ness] <expr> # set thickness of lines <br>
chop [<expr>] # chop end(s) of segment <br>
’->’ | ’<-’ |
’<->’ # decorate with arrows <br>
invis[ible] # make primitive invisible <br>
solid # make closed figure solid <br>
fill[ed] [<expr>] # set fill density for figure <br>
xscaled <expr> # slant box into x direction <br>
yscaled <expr> # slant box into y direction <br>
colo[u]r[ed] TEXT # set fill and outline color for figure
<br>
outline[d] TEXT # set outline color for figure <br>
shaded TEXT # set fill color for figure <br>
same # copy size of previous object <br>
cw | ccw # set orientation of curves <br>
ljust | rjust # adjust text horizontally <br>
above | below # adjust text vertically <br>
aligned # align parallel to object <br>
TEXT TEXT ... # text within object <br>
<expr> # motion in the current direction</font></p>
<p style="margin-top: 1em"><font color="#000000">Missing
attributes are supplied from defaults; inappropriate ones
are silently ignored. For lines, splines, and arcs, height
and width refer to arrowhead size.</font></p>
<p style="margin-top: 1em"><font color="#000000">The
‘at’ primitive sets the center of the current
object. The ‘with’ attribute fixes the specified
feature of the given object to a specified location. (Note
that ‘with’ is incorrectly described in the
Kernighan paper.)</font></p>
<p style="margin-top: 1em"><font color="#000000">The
‘by’ primitive is not documented in the tutorial
portion of the Kernighan paper, and should probably be
considered unreliable.</font></p>
<p style="margin-top: 1em"><font color="#000000">The
primitive ‘arrow’ is a synonym for
‘line ->’.</font></p>
<p style="margin-top: 1em"><font color="#000000">Text is
normally an attribute of some object, in which case
successive strings are vertically stacked and centered on
the object’s center by default. Standalone text is
treated as though placed in an invisible box.</font></p>
<p style="margin-top: 1em"><font color="#000000">A text
item consists of a string or sprintf-expression, optionally
followed by positioning information. Text (or strings
specified with ‘sprintf’) may contain font
changes, size changes, and local motions, provided those
changes are undone before the end of the current item. Text
may also contain \-escapes denoting special characters. The
base font and specific set of escapes supported is
implementation dependent, but supported escapes always
include the following:</font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="16%">
<p style="margin-top: 1em"><font color="#000000">\fR,
\f1</font></p> </td>
<td width="84%">
</td></tr>
</table>
<p style="margin-left:10%;"><font color="#000000">Set Roman
style (the default)</font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="16%">
<p style="margin-top: 1em"><font color="#000000">\fI,
\f2</font></p> </td>
<td width="84%">
</td></tr>
</table>
<p style="margin-left:10%;"><font color="#000000">Set
Italic style</font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="16%">
<p style="margin-top: 1em"><font color="#000000">\fB,
\f3</font></p> </td>
<td width="84%">
</td></tr>
</table>
<p style="margin-left:10%;"><font color="#000000">Set Bold
style</font></p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="18%">
<p style="margin-top: 1em"><font color="#000000">\fP </font></p> </td>
<td width="82%">
</td></tr>
</table>
<p style="margin-left:10%;"><font color="#000000">Revert to
previous style; only works one level deep, does not
stack.</font></p>
<p style="margin-top: 1em"><font color="#000000">Color
names are dependent on the pic implementation, but in all
modern versions color names recognized by the X window
system are supported.</font></p>
<p style="margin-top: 1em"><font color="#000000">A position
is an (x,y) coordinate pair. There are lots of different
ways to specify positions:</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><position>
::= <br>
<position-not-place> <br>
<place> <br>
( <position> )</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><position-not-place>
::= <br>
<expr-pair> <br>
<position> + <expr-pair> <br>
<position> - <expr-pair> <br>
( <position> , <position> ) <br>
<expr> [of the way] between <position> and
<position> <br>
<expr> ’<’ <position> ,
<position> ’>’</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><expr-pair>
::= <br>
<expr> , <expr> <br>
( expr-pair )</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><place>
::= <br>
<label> <br>
<label> <corner> <br>
<corner> [of] <label> <br>
Here</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><label>
::= <br>
LABEL [. LABEL ...] <br>
<nth-primitive></font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><corner>
::= <br>
.n | .e | .w | .s <br>
.ne | .se | .nw | .sw <br>
.c[enter] | .start | .end <br>
.t[op] | .b[ot[tom]] | .l[eft] | .r[ight] <br>
left | right | <top-of> | <bottom-of> <br>
<north-of> | <south-of> | <east-of> |
<west-of> <br>
<center-of> | <start-of> | <end-of> <br>
upper left | lower left | upper right | lower
right</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><<i>xxx</i>-of>
::= <i><br>
xxx</i> # followed by ‘of’</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><nth-primitive>
::= <br>
<ordinal> <object-type> <br>
[<ordinal>] last <object-type></font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><ordinal>
::= <br>
INT th <br>
INT st | INT nd | INT rd <br>
‘ <any-expr> ’th</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><object-type>
::= <br>
box <br>
circle <br>
ellipse <br>
arc <br>
line <br>
arrow <br>
spline <br>
’[]’ <br>
TEXT</font></p>
<p style="margin-top: 1em"><font color="#000000">As
Kernighan notes, “since barbarisms like <b>1th</b> and
<b>3th</b> are barbaric, synonyms like <b>1st</b> and
<b>3rd</b> are accepted as well.” Objects of a given
type are numbered from 1 upwards in order of declaration;
the <b>last</b> modifier counts backwards.</font></p>
<p style="margin-top: 1em"><font color="#000000">The
“’th” form (which allows you to select a
previous object with an expression, as opposed to a numeric
literal) is not documented in DWB’s
<i>pic</i>(1).</font></p>
<p style="margin-top: 1em"><font color="#000000">The ⟨
<i>xxx</i>-of⟩ rule is special: The lexical parser
checks whether <i>xxx</i> is followed by the token
‘of’ without eliminating it so that the grammar
parser can still see ‘of’. Valid examples of
specifying a place with corner and label are thus</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000">A
.n <br>
.n of A <br>
.n A <br>
north of A</font></p>
<p style="margin-top: 1em"><font color="#000000">while</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000">north
A <br>
A north</font></p>
<p style="margin-top: 1em"><font color="#000000">both cause
a syntax error. (DWB <b>pic</b> also allows the weird form
‘A north of’.)</font></p>
<p style="margin-top: 1em"><font color="#000000">Here the
special rules for the ‘with’ keyword using a
path:</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><path>
::= <br>
<relative-path> <br>
( <relative-path> , <relative-path> )</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><relative-path>
::= <br>
<corner> <br>
. LABEL [. LABEL ...] [<corner>]</font></p>
<p style="margin-top: 1em"><font color="#000000">The
following style variables control output:</font></p>
<p align="center"><font color="#000000"><img src="img/pic51.png" alt="Image img/pic51.png"></font></p>
<p><font color="#000000">Any of these can be set by
assignment, or reset using the <b>reset</b> statement. Style
variables assigned within ‘[ ]’ blocks are
restored to their beginning-of-block value on exit;
top-level assignments persist across pictures. Dimensions
are divided by <b>scale</b> on output.</font></p>
<p style="margin-top: 1em"><font color="#000000">All
<b>pic</b> expressions are evaluated in floating point;
units are always inches (a trailing ‘i’ or
‘I’ is ignored). Expressions have the following
simple grammar, with semantics very similar to
C expressions:</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><expr>
::= <br>
VARIABLE <br>
NUMBER <br>
<place> <place-attribute> <br>
<expr> <op> <expr> <br>
- <expr> <br>
( <any-expr> ) <br>
! <expr> <br>
<func1> ( <any-expr> ) <br>
<func2> ( <any-expr> , <any-expr> ) <br>
rand ( )</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><place-attribute>
<br>
.x | .y | .h[eigh]t | .wid[th] | .rad</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><op>
::= <br>
+ | - | * | / | % | ^ | ’<’ |
’>’ | ’<=’ |
’>=’</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><func1>
::= <br>
sin | cos | log | exp | sqrt | int | rand | srand</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><func2>
::= <br>
atan2 | max | min</font></p>
<p style="margin-top: 1em"><font color="#000000">Both
<b>exp</b> and <b>log</b> are base 10; <b>int</b> does
integer truncation; and <b>rand()</b> returns a random
number in [0-1).</font></p>
<p style="margin-top: 1em"><font color="#000000">There are
<b>define</b> and <b>undef</b> statements which are not part
of the grammar (they behave as pre-processor macros to the
language). These may be used to define
pseudo-functions.</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><b>define</b>
<i>name</i> <b>{</b> <i>replacement-text</i>
<b>}</b></font></p>
<p style="margin-top: 1em"><font color="#000000">This
defines <i>name</i> as a macro to be replaced by the
replacement text (not including the braces). The macro may
be called as</font></p>
<p style="margin-left:10%; margin-top: 1em"><font color="#000000"><i>name</i><b>(</b><i>arg1,
arg2, ..., argn</i><b>)</b></font></p>
<p style="margin-top: 1em"><font color="#000000">The
arguments (if any) are substituted for tokens $1, $2 ... $n
appearing in the replacement text. To undefine a macro, say
<b>undef</b> <i>name</i>, specifying the name to be
undefined.</font></p>
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