(eplain.info)Slanted lines and vectors

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6.1 Slanted lines and vectors
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The macros '\drawline' and '\drawvector' provide the capability found in
LaTeX's picture mode to draw slanted lines and vectors of certain
directions. Both of these macros take three arguments: two integer
arguments to specify the direction of the line or vector, and one
argument to specify its length. For example, '\drawvector(-4,1){60pt}'
produces the vector

      (A vector in the 2d quadrant of length 60 pt appears here.)

   which lies in the 2d quadrant, has a slope of minus 1/4, and a width
of 60 pt.

   Note that if an '\hbox' is placed around '\drawline' or
'\drawvector', then the width of the '\hbox' will be the positive
dimension specified in the third argument, except when a vertical line
or vector is specified, e.g., '\drawline(0,1){1in}', which has zero
width. If the specified direction lies in the 1st or 2d quadrant (e.g.,
'(1,1)' or '(-2,3)'), then the '\hbox' will have positive height and
zero depth. Conversely, if the specified direction lies in the 3d or 4th
quadrant (e.g., '(-1,-1)' or '(2,-3)'), then the '\hbox' will have
positive depth and zero height.

   There are a finite number of directions that can be specified. For
'\drawline', the absolute value of each integer defining the direction
must be less than or equal to six, i.e., '(7,-1)' is incorrect, but
'(6,-1)' is acceptable. For '\drawvector', the absolute value of each
integer must be less than or equal to four. Furthermore, the two
integers cannot have common divisors; therefore, if a line with slope 2
is desired, say '(2,1)' instead of '(4,2)'. Also, specify '(1,0)'
instead of, say, '(3,0)' for horizontal lines and likewise for vertical
lines.

   Finally, these macros depend upon the LaTeX font 'line10'. If your
site doesn't have this font, ask your system administrator to get it.
Future enhancements will include macros to draw dotted lines and dotted
vectors of various directions.