From martinsluka at mac.com  Sat Apr 13 14:44:51 2024
From: martinsluka at mac.com (Martin Sluka)
Date: Sat, 13 Apr 2024 14:44:51 +0200
Subject: [metapost] Bricks wall
Message-ID: <202404132220.43DMKAtq023487@freefriends.org>

Hi, 

May you send me a sample of Metapost macro which generate bricks wall?

Thanks

Martin

From thurston at eml.cc  Sun Apr 28 17:21:12 2024
From: thurston at eml.cc (Toby Thurston)
Date: Sun, 28 Apr 2024 16:21:12 +0100
Subject: [metapost] New number systems compute cyclic path strangely
Message-ID: <13623789-046E-4215-8192-1A0536068135@eml.cc>

This recent question on TexSE seems to have uncovered an anomaly in the way that MP computes the `arclength` of cyclic paths when using any of the new number systems.  

https://tex.stackexchange.com/q/716630/15036


The poster supplied this example code

beginfig(1);
path p;
p = (0,0){up}..{right}(200,100)..{up}(300,400)..cycle;
len := arclength p;
s := arctime (2500) of p;
t := arctime (len+2500) of p;
draw p;
show len;% 2799
show s;% 2.92...
show t;% 2.67...
show arctime arclength p of p;
show numbersystem;

endfig;
end

With the default number system the value of t is 5.92... as you might expect, but with any of the new number systems the value is 2.67.....

The original poster as TeX.SE was using MP 2.02 but I I see this behaviour with  MetaPost, version 2.10 (TeX Live 2024).

Toby
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From j.hagen at xs4all.nl  Sun Apr 28 19:16:19 2024
From: j.hagen at xs4all.nl (Hans Hagen)
Date: Sun, 28 Apr 2024 19:16:19 +0200
Subject: [metapost] New number systems compute cyclic path strangely
In-Reply-To: <13623789-046E-4215-8192-1A0536068135@eml.cc>
References: <13623789-046E-4215-8192-1A0536068135@eml.cc>
Message-ID: <a0f5ed6b-df4d-437b-b7ef-6aa484c782f2@xs4all.nl>

On 4/28/2024 5:21 PM, Toby Thurston wrote:
> This recent question on TexSE seems to have uncovered an anomaly in the 
> way that MP computes the `arclength` of cyclic paths when using any of 
> the new number systems.
> 
> https://tex.stackexchange.com/q/716630/15036 
> <https://tex.stackexchange.com/q/716630/15036>
> 
> 
> The poster supplied this example code
> 
> beginfig(1);
> path p;
> p = (0,0){up}..{right}(200,100)..{up}(300,400)..cycle;
> len := arclength p;
> s := arctime (2500) of p;
> t := arctime (len+2500) of p;
> draw p;
> show len;% 2799
> show s;% 2.92...
> show t;% 2.67...
> show arctime arclength p of p;
> show numbersystem;
> 
> endfig;
> end
> 
> With the default number system the value of t is 5.92... as you might 
> expect, but with any of the new number systems the value is 2.67.....

fwiw: len (2800) + 2500 also exceeds 4096 which is scaled max so the 
fact that scaled works is kind of a miracle


-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------


From luigi.scarso at gmail.com  Mon Apr 29 09:05:46 2024
From: luigi.scarso at gmail.com (luigi scarso)
Date: Mon, 29 Apr 2024 09:05:46 +0200
Subject: [metapost] New number systems compute cyclic path strangely
In-Reply-To: <13623789-046E-4215-8192-1A0536068135@eml.cc>
References: <13623789-046E-4215-8192-1A0536068135@eml.cc>
Message-ID: <CAG5iGsCxc28xYanNi3Pyr=EU=0COOO5uDjuGP1djUc9kRxV4BQ@mail.gmail.com>

On Sun, 28 Apr 2024 at 17:21, Toby Thurston <thurston at eml.cc> wrote:

> This recent question on TexSE seems to have uncovered an anomaly in the
> way that MP computes the `arclength` of cyclic paths when using any of the
> new number systems.
>
> https://tex.stackexchange.com/q/716630/15036
>
>
> The poster supplied this example code
>
> beginfig(1);
> path p;
> p = (0,0){up}..{right}(200,100)..{up}(300,400)..cycle;
> len := arclength p;
> s := arctime (2500) of p;
> t := arctime (len+2500) of p;
> draw p;
> show len;% 2799
> show s;% 2.92...
> show t;% 2.67...
> show arctime arclength p of p;
> show numbersystem;
>
> endfig;
> end
>
> With the default number system the value of t is 5.92... as you might
> expect, but with any of the new number systems the value is 2.67.....
>
> The original poster as TeX.SE was using MP 2.02 but I I see this behaviour
> with  MetaPost, version 2.10 (TeX Live 2024).
>
> Toby
> --
> http://tug.org/metapost/


I will check asap.

--
luigi
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From luigi.scarso at gmail.com  Mon Apr 29 20:11:38 2024
From: luigi.scarso at gmail.com (luigi scarso)
Date: Mon, 29 Apr 2024 20:11:38 +0200
Subject: [metapost] New number systems compute cyclic path strangely
In-Reply-To: <13623789-046E-4215-8192-1A0536068135@eml.cc>
References: <13623789-046E-4215-8192-1A0536068135@eml.cc>
Message-ID: <CAG5iGsC48EkvKpVKAPCDXoe1sT5W2Ef0jasPejnpaYPo+=asCQ@mail.gmail.com>

On Sun, 28 Apr 2024 at 17:21, Toby Thurston <thurston at eml.cc> wrote:

> This recent question on TexSE seems to have uncovered an anomaly in the
> way that MP computes the `arclength` of cyclic paths when using any of the
> new number systems.
>
> https://tex.stackexchange.com/q/716630/15036
>
>
> The poster supplied this example code
>
> beginfig(1);
> path p;
> p = (0,0){up}..{right}(200,100)..{up}(300,400)..cycle;
> len := arclength p;
> s := arctime (2500) of p;
> t := arctime (len+2500) of p;
> draw p;
> show len;% 2799
> show s;% 2.92...
> show t;% 2.67...
> show arctime arclength p of p;
> show numbersystem;
>
> endfig;
> end
>
> With the default number system the value of t is 5.92... as you might
> expect, but with any of the new number systems the value is 2.67.....
>
> The original poster as TeX.SE was using MP 2.02 but I I see this behaviour
> with  MetaPost, version 2.10 (TeX Live 2024).
>
> Toby
> --
> http://tug.org/metapost/


Hm I fear that
 @<Update |arc| and |t_tot| after |do_arc_test| has just returned |t|@>;
implicitly uses the fact that scaled is an integer type, i.e.
set_number_from_div (n1, arc, d1); /* n1 = (arc / d1) */
and
number_add (v1, epsilon_t);       /* v1 = n1+1 */
look suspicious in double mode  ( epsilon_t is not 1 but 2^-52, 1 is unity
)

--
luigi
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