PIC(1)

NAME

pic, tpic − troff and tex preprocessors for drawing pictures

SYNOPSIS

pic [ files ]

tpic [ files ]

DESCRIPTION

Pic is a troff(1) preprocessor for drawing figures on a typesetter. Pic code is contained between .PS and .PE lines:

.PS optional-width optional-height
element-list
.PE

or in a file mentioned in a .PS line:

.PS

If optional-width is present, the picture is made that many inches wide, regardless of any dimensions used internally. The height is scaled in the same proportion unless optional-height is present. If .PF is used instead of .PE, the typesetting position after printing is restored to what it was upon entry.

An element-list is a list of elements:

primitive attribute-list
placename : element
placename : position
var = expr
direction
{ element-list }
[ element-list ]
for var = expr to expr by expr do { anything }
if expr then { anything } else { anything }
copy file, copy thru macro, copy file thru macro
sh { commandline }
print expr
reset optional var-list
troff-command

Elements are separated by newlines or semicolons; a long element may be continued by ending the line with a backslash. Comments are introduced by a # and terminated by a newline. Variable names begin with a lower case letter; place names begin with upper case. Place and variable names retain their values from one picture to the next.

After each primitive the current position moves in the current direction (up,down, left,right (default)) by the size of the primitive. The current position and direction are saved upon entry to a {...} block and restored upon exit. Elements within a block enclosed in [...] are treated as a unit; the dimensions are determined by the extreme points of the contained objects. Names, variables, and direction of motion within a block are local to that block.

Troff-command is any line that begins with a period. Such a line is assumed to make sense in the context where it appears; generally, this means only size and font changes.

The primitive objects are:

box circle ellipse arc line arrow spline move text-list

arrow is a synonym for line ->.

An attribute-list is a sequence of zero or more attributes; each attribute consists of a keyword, perhaps followed by a value.

h(eigh)t exprwid(th) expr
rad(ius) exprdiam(eter) expr
up opt-exprdown opt-expr
right opt-exprleft opt-expr
from positionto position
at positionwith corner
by expr, exprthen
dotted opt-exprdashed opt-expr
chop opt-expr-> <- <->
invissame
fill opt-expr
text-listexpr

Missing attributes and values are filled in from defaults. Not all attributes make sense for all primitives; irrelevant ones are silently ignored. The attribute at causes the geometrical center to be put at the specified place; with causes the position on the object to be put at the specified place. For lines, splines and arcs, height and width refer to arrowhead size. A bare expr implies motion in the current direction.

Text is normally an attribute of some primitive; by default it is placed at the geometrical center of the object. Stand-alone text is also permitted. A text list is a list of text items:

text-item:
"..." positioning ...
sprintf("format", expr, ...) positioning ...
positioning:
center ljust rjust above below

If there are multiple text items for some primitive, they are arranged vertically and centered except as qualified. Positioning requests apply to each item independently. Text items may contain troff commands for size and font changes, local motions, etc., but make sure that these are balanced so that the entering state is restored before exiting.

A position is ultimately an x,y coordinate pair, but it may be specified in other ways.

position:
expr, expr
place ± expr, expr
place ± ( expr, expr )
( position, position )x from one, y the other
expr [of the way] between position and position
expr < position , position >
( position )

place:
placename optional-corner
corner of placename
nth primitive optional-corner
corner of nth primitive
Here

An optional-corner is one of the eight compass points or the center or the start or end of a primitive.

optional-corner:
.n .e .w .s .ne .se .nw .sw .c .start .end
corner:
top bot left right start end

Each object in a picture has an ordinal number; nth refers to this.

nth:
nth, nth last

The built-in variables and their default values are:

boxwid 0.75boxht 0.5
circlerad 0.25arcrad 0.25
ellipsewid 0.75ellipseht 0.5
linewid 0.5lineht 0.5
movewid 0.5moveht 0.5
textwid 0textht 0
arrowwid 0.05arrowht 0.1
dashwid 0.1arrowhead 2
scale 1

These may be changed at any time, and the new values remain in force from picture to picture until changed again or reset by a reset statement. Variables changed within [ and ] revert to their previous value upon exit from the block. Dimensions are divided by scale during output.

Expressions in pic are evaluated in floating point. All numbers representing dimensions are taken to be in inches.

expr:
expr op expr
- expr
! expr
( expr )
variable
number
place .x place .y place .ht place .wid place .rad
sin(expr) cos(expr) atan2(expr,expr) log(expr) exp(expr)
sqrt(expr) max(expr,expr) min(expr,expr) int(expr) rand()
op:
+ - ∗ / % < <= > >= == != && ||

The define and undef statements are not part of the grammar.

define name { replacement text }
undef name

Occurrences of $1, $2, etc., in the replacement text will be replaced by the corresponding arguments if name is invoked as

name(arg1, arg2, ...)

Non-existent arguments are replaced by null strings. Replacement text may contain newlines. The undef statement removes the definition of a macro.

Tpic is a tex(1) preprocessor that accepts pic language. It produces Tex commands that define a box called \graph, which contains the picture. The box may be output this way:

\centerline{\box\graph}

EXAMPLES

arrow "input" above; box "process"; arrow "output" above
move
A: ellipse
   circle rad .1 with .w at A.e
   circle rad .05 at 0.5 <A.c, A.ne>
   circle rad .065 at 0.5 <A.c, A.ne>
   spline from last circle.nw left .25 then left .05 down .05
   arc from A.c to A.se rad 0.5
   for i = 1 to 10 do { line from A.s+.025∗i,.01∗i down i/50 }

arrow "input" above; box "process"; arrow "output" above move A: ellipse
   circle rad .1 with .w at A.e
   circle rad .05 at 0.5 <A.c, A.ne>
   circle rad .065 at 0.5 <A.c, A.ne>
   spline from last circle.nw left .25 then left .05 down .05
   arc from A.c to A.se rad 0.5
   for i = 1 to 10 do { line from A.s+.025∗i,.01∗i down i/50 }

SOURCE

/sys/src/cmd/pic

Museum