mfpic-doc.pdf.

4.2 COMMON OBJECTS. 15
after the command \pointdef{A}(1,3), \A expands to (1,3), while \Ax and \Ay expand to 1 and
3, respectively. If mplabels is in effect one can use \A to specify where to place a text label, but if
TEX is placing labels one must use (\Ax,\Ay). In most other cases, one can use \A where a pair or
point is required.
\polyline{〈p 0 〉,〈p 1 〉,...}
\lines{〈p 0 〉,〈p 1 〉,...}
The figure macro \polyline produces connected line segments from 〈p 0 〉 to 〈p 1 〉, and from
there to 〈p 2 〉, etc. The result is an open polygonal path through the specified points, in the specified
order. The macro \lines is an alias for \polyline.
\polygon{〈p 0 〉,〈p 1 〉,...}
\closedpolyline{〈p 0 〉,〈p 1 〉,...}
The figure macro \polygon produces a closed polygon with vertices at the specified points in
the specified order. It works exactly like \polyline except the last point in the list is also joined to
the first. The macro \closedpolyline is an alias for \polygon.
\rect{〈p 0 〉,〈p 1 〉}
This figure macro produces the closed rectangle with horizontal and vertical sides, having the
points 〈p 0 〉 and 〈p 1 〉 as diagonally opposite corners. The same rectangle can be specified in four
different ways: either pair of opposite corners in either order.
It is occasionally helpful to know that connected paths like those produced by \polyline or
\rect have a start and a finish as well as sense (or direction). The path produced by \polyline
starts at the first listed point and ends at last, having the direction determined by the order of the
points. For \rect the sense may be clockwise or anticlockwise depending on the corners used:
it starts by moving horizontally from the first listed point. Several MFPIC macros (such as those
that add arrowheads) treat the beginning and the end of a path differently, or adjust their behavior
according to the sense of the curve.
\regpolygon{〈num〉}{〈name〉}{〈eqn 1 〉}{〈eqn 2 〉}
This figure macro produces a closed regular polygon with 〈num〉 sides. The second argument,
〈name〉 is a symbolic name. It can be used to refer to the vertices later. The last two arguments should
be equations that position two of the vertices or one vertex and the center. The center is referred to
by 〈name〉0 and the vertices by 〈name〉1 〈name〉2, etc., going anticlockwise around the polygon.
The 〈name〉 itself (without a number suffixed) will be a METAFONT variable assigned the value of
〈num〉. For example,
\regpolygon{5}{Kay}{Kay0=(0,1)}{Kay1=(2,0)}
will produce a regular pentagon with its center at (0,1) and its first vertex at (2,0). One could later
draw a star inside it with
\polygon{Kay1,Kay3,Kay5,Kay2,Kay4}
Moreover, Kay will equal 5. The name given becomes a METAFONT variable and care should be
taken to make the name distinctive so as not to redefine some internal variable.
4.2.2 A WORD ABOUT LIST ARGUMENTS
We have seen already four MFPIC macros that take a mandatory argument consisting of an arbitrary
number of coordinate pairs, separated by commas. There are many more, and some that take a
comma-separated list of items of other types. If the lists are long, especially if they are generated by