glenda.party
term% ls -F
term% cat index.txt
PIC(1)                      General Commands Manual                     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 optional-width optional-height <file

       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  direc‐
       tion (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
       is a synonym for

       An attribute-list is a sequence of zero or more attributes; each attri‐
       bute consists of a keyword, perhaps followed by a value.
            h(eigh)t expr       wid(th) expr
            rad(ius) expr       diam(eter) expr
            up opt-expr         down opt-expr
            right opt-expr      left opt-expr
            from position       to position
            at position         with corner
            by expr, expr       then
            dotted opt-expr     dashed opt-expr
            chop opt-expr       ->  <-  <->
            invis               same
            text-list           expr
       Missing attributes and values are filled in from defaults.  Not all at‐
       tributes make sense for all primitives; irrelevant  ones  are  silently
       ignored.   The attribute causes the geometrical center to be put at the
       specified place; causes the position on the object to  be  put  at  the
       specified  place.   For lines, splines and arcs, and 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 ap‐
       ply 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  exit‐
       ing.

       A  position  is ultimately an x,y coordinate pair, but it may be speci‐
       fied 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 0.75         boxht 0.5
            circlerad 0.25      arcrad 0.25
            ellipsewid 0.75     ellipseht 0.5
            linewid 0.5         lineht 0.5
            movewid 0.5         moveht 0.5
            textwid 0           textht 0
            arrowwid 0.05       arrowht 0.1
            dashwid 0.1         arrowhead 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  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 repre‐
       senting 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 pic‐
       ture.  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:  el‐
       lipse
          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

SEE ALSO
       grap(1), doctype(1), troff(1)
       B.  W. Kernighan, ``PIC—a Graphics Language for Typesetting'', Unix Re‐
       search System Programmer's Manual, Tenth Edition, Volume 2



                                                                        PIC(1)