Postfix specification graphics, etc.
- To: mathgroup at smc.vnet.net
- Subject: [mg118437] Postfix specification graphics, etc.
- From: "Christopher O. Young" <cy56 at comcast.net>
- Date: Thu, 28 Apr 2011 06:34:44 -0400 (EDT)
I think I'm finally catching on to the pure function notation enough to put
everything into the kind of postfix notation I prefer. It just seems
preferable to me to have the geometrical objects positioned first, where
they're most prominent, and have the commands that modify their display
following them.
For example, the following plots a "trammel" sliding in a corner, always
tangent to the same hyperbola. All the lines are colored with corresponding
colors for the points.
P = {{0, k}, {10 - k, 0}}~Table~{k, 0, 10};
(* Points for the lines *)
S = Drop[P, {}, {2}] // Flatten[#, 1] &;
(* The start points *)
F = P // Drop[#, {}, {1}] & // Flatten[#, 1] &;
(* The finish points *)
({
Line[{S[[j]], F[[j]]}] // {Hue[0.8 (j - 1)/9],Thickness[0.02], #} &,
{Point[S[[j]]], Point[F[[j]]]} //{Hue[0.8 (j - 1)/9],PointSize[0.05],#} &
}
~Table~{j, 1, 11})\
// Graphics
It's a little irritating to have to add parentheses to get Graphics to have
enough scope, and a backslash to continue to the next line, but I still like
getting the lines and points first.
One interesting thing here is that
{Hue[0.8 (j - 1)/9],Thickness[0.02], #} &
is being used as a pure function, i.e., the list function, so that I can
list each set of graphics directives after the objects they modify.
Also it's lucky that I can get away with putting the points in a list and
then applying the directives via another list, since I haven't been able to
get it to work via numbered slots (i.e., #1, #2, etc.).
I don't think it's accidental that the "//" form resembles the "pipe"
operator from Unix, since it seems to be possible to use it for the same
purpose, to "pipe" the output of one command into another.
One question: How do I get all the points to plot on top?
Chris Young
cy56 at comcast.net
IntuMath.org