* MetaPost transformation
@ 2012-05-30 21:10 Troy Henderson
2012-05-30 21:30 ` Hans Hagen
2012-05-31 7:00 ` Albrecht Kauffmann
0 siblings, 2 replies; 7+ messages in thread
From: Troy Henderson @ 2012-05-30 21:10 UTC (permalink / raw)
To: MetaPost List, mailing list for ConTeXt users
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I've encountered a MetaPost issue, and since many MetaPost users also use
ConTeXt (and vice-versa), I am posting this question on both lists.
The command
> show identity rotated 270 yscaled 0.5;
outputs
(0,0,0,1,-0.5,0)
as expected, while the command
> show identity transformed (0,0,0,1,-0.5,0);
errors with
---
! Missing `)' has been inserted.
<to be read again>
,
l.26 ^^Ishow identity transformed (0,0,0,1,
-0.5,0);
---
I am using MetaPost 1.504, and the problem seems to be that MetaPost does
not like me using the sextuple (0,0,0,1,-0.5,0) directly, but this is the
most convenient method for me to describe my transformations. Is this a
bug in MetaPost, or am I not allowed to use transformations directly with
sextuples?
Troy Henderson
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: MetaPost transformation
2012-05-30 21:10 MetaPost transformation Troy Henderson
@ 2012-05-30 21:30 ` Hans Hagen
2012-05-31 0:56 ` Troy Henderson
2012-05-31 7:00 ` Albrecht Kauffmann
1 sibling, 1 reply; 7+ messages in thread
From: Hans Hagen @ 2012-05-30 21:30 UTC (permalink / raw)
To: mailing list for ConTeXt users; +Cc: MetaPost List
On 30-5-2012 23:10, Troy Henderson wrote:
> I've encountered a MetaPost issue, and since many MetaPost users also use
> ConTeXt (and vice-versa), I am posting this question on both lists.
>
> The command
>
>> show identity rotated 270 yscaled 0.5;
>
> outputs
>
> (0,0,0,1,-0.5,0)
>
> as expected, while the command
>
>> show identity transformed (0,0,0,1,-0.5,0);
>
> errors with
>
> ---
> ! Missing `)' has been inserted.
> <to be read again>
> ,
> l.26 ^^Ishow identity transformed (0,0,0,1,
> -0.5,0);
> ---
>
> I am using MetaPost 1.504, and the problem seems to be that MetaPost does
> not like me using the sextuple (0,0,0,1,-0.5,0) directly, but this is the
> most convenient method for me to describe my transformations. Is this a
> bug in MetaPost, or am I not allowed to use transformations directly with
> sextuples?
It looks like sextuples are no basic datatype. I think that the show is
just a way to output the internal representation. Of course it would
make sense to have sixtuples (I can even think of a generic n-tuple).
Hans
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___________________________________________________________________________________
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: MetaPost transformation
2012-05-30 21:30 ` Hans Hagen
@ 2012-05-31 0:56 ` Troy Henderson
[not found] ` <CAFP+xFJmoZ0PBWK=91SY7jPmEa_4gWGSBHfnt6S659jEiQCbAg@mail.g mail.com>
0 siblings, 1 reply; 7+ messages in thread
From: Troy Henderson @ 2012-05-31 0:56 UTC (permalink / raw)
To: Hans Hagen; +Cc: mailing list for ConTeXt users, MetaPost List
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Well then in case anyone needs such a transformation, I've constructed the
(non-unique) transformation T
> t:=angle(f,e);
> q:=e++f;
> p:=(c*f-d*e)/q;
> s:=(c*e+d*f)/(q**2);
> transform T;
> T:=identity rotated t xscaled p yscaled q slanted s shifted (a,b);
This yields T=(a,b,c,d,e,f).
Troy
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___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!
maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage : http://www.pragma-ade.nl / http://tex.aanhet.net
archive : http://foundry.supelec.fr/projects/contextrev/
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___________________________________________________________________________________
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: MetaPost transformation
2012-05-30 21:10 MetaPost transformation Troy Henderson
2012-05-30 21:30 ` Hans Hagen
@ 2012-05-31 7:00 ` Albrecht Kauffmann
2012-05-31 12:31 ` Troy Henderson
1 sibling, 1 reply; 7+ messages in thread
From: Albrecht Kauffmann @ 2012-05-31 7:00 UTC (permalink / raw)
To: mailing list for ConTeXt users; +Cc: MetaPost List
Hello Troy,
if you declare a transform variable (e.g., t), it works:
transform t;
t := identity rotated 270 yscaled 0.5;
show identity transformed t;
>> (0,0,0,1,-0.5,0)
Greetings
Albrecht
On Wed, 30 May 2012, Troy Henderson wrote:
> I've encountered a MetaPost issue, and since many MetaPost users also use
> ConTeXt (and vice-versa), I am posting this question on both lists.
>
> The command
>
>> show identity rotated 270 yscaled 0.5;
>
> outputs
>
> (0,0,0,1,-0.5,0)
>
> as expected, while the command
>
>> show identity transformed (0,0,0,1,-0.5,0);
>
> errors with
>
> ---
> ! Missing `)' has been inserted.
> <to be read again>
> ,
> l.26 ^^Ishow identity transformed (0,0,0,1,
> -0.5,0);
> ---
>
> I am using MetaPost 1.504, and the problem seems to be that MetaPost does
> not like me using the sextuple (0,0,0,1,-0.5,0) directly, but this is the
> most convenient method for me to describe my transformations. Is this a
> bug in MetaPost, or am I not allowed to use transformations directly with
> sextuples?
>
> Troy Henderson
>
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!
maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage : http://www.pragma-ade.nl / http://tex.aanhet.net
archive : http://foundry.supelec.fr/projects/contextrev/
wiki : http://contextgarden.net
___________________________________________________________________________________
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2012-05-31 12:31 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2012-05-30 21:10 MetaPost transformation Troy Henderson
2012-05-30 21:30 ` Hans Hagen
2012-05-31 0:56 ` Troy Henderson
[not found] ` <CAFP+xFJmoZ0PBWK=91SY7jPmEa_4gWGSBHfnt6S659jEiQCbAg@mail.g mail.com>
2012-05-31 2:37 ` [NTG-context] " Dan Luecking
2012-05-31 3:44 ` [metapost] " Troy Henderson
2012-05-31 7:00 ` Albrecht Kauffmann
2012-05-31 12:31 ` Troy Henderson
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