Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.soft-sys.math.mathematica > #1980 > unrolled thread

Re: Postfix specification graphics, etc.

Back to article view | Back to comp.soft-sys.math.mathematica

Contents

  Re: Postfix specification graphics, etc. DrMajorBob <btreat1@austin.rr.com> - 2011-04-29 11:31 +0000

#1980 — Re: Postfix specification graphics, etc.

I can find no documentation of this form of Drop:

Drop[P, {}, {2}]

but the expression appears to have the same effect as

Drop[P, None, {2}]

which is... slightly... barely... buried deep... but vaguely documented.

Also note that

P[[All, -1]]

or

P[[All, 2]]

is equivalent to, simpler, and far more obvious, I think, compared to

P // Drop[#, None, {1}] & // Flatten[#, 1] &

Bobby

On Thu, 28 Apr 2011 05:34:44 -0500, Christopher O. Young  
<cy56@comcast.net> wrote:

> 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@comcast.net
> IntuMath.org
>
>
>


-- 
DrMajorBob@yahoo.com

[toc] | [standalone]

Back to top | Article view | comp.soft-sys.math.mathematica

csiph-web