[NTG-context] Different behavior of \clf_lastypos vs \clf_lastxpos

[NTG-context] Different behavior of \clf_lastypos vs \clf_lastxpos

[Aditya Mahajan]

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Hi,

I am trying to debug an unexpected behavior with tikz reported on tex.se: https://tex.stackexchange.com/q/696136/323

The attached file shows what is going wrong (without using tikz). For some reason, there is an extra \relax written to file after `\the\numexp\clf_lastypos\relax` (there is no such relax after `\the\numexpr\clf_lastxpos\relax`). The test.pgf file is:

  \macro {A}{23930350}{43358454.0\relax }
  \macro {B}{39564274.0\relax }{14083538}

Any ideas on why is the extra \relax written after lastypos and how to fix that?

Aditya

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[NTG-context] Re: Different behavior of \clf_lastypos vs \clf_lastxpos

[Max Chernoff]

Hi Aditya,

> For some reason, there is an extra \relax written to file after
> `\the\numexp\clf_lastypos\relax` (there is no such relax after
> `\the\numexpr\clf_lastxpos\relax`). The test.pgf file is:
> 
> \macro {A}{23930350}{43358454.0\relax } \macro {B}{39564274.0\relax
>   }{14083538}
> 
> Any ideas on why is the extra \relax written after lastypos and how to
> fix that?

\numexpr stops at the first non-expandable or non-digit token. If
\clf_last[xy]pos expands to an integer, then that's the \relax, but if
it expands to a float, then that's the decimal point. 

With Lua, adding, subtracting, or multiplying two integers will give you
an integer, but dividing gives you a float. So somewhere in the backend,
the vertical position is probably divided but the horizontal position is
only added or subtracted.

To fix this, change lines 2344--2345 of anch-pos.lmt from

   implement { name = "lastxpos", actions = function() context(jobpositions.lastx) end }
   implement { name = "lastypos", actions = function() context(jobpositions.lasty) end }

to

   implement { name = "lastxpos", actions = function() context("%.0f", jobpositions.lastx) end }
   implement { name = "lastypos", actions = function() context("%.0f", jobpositions.lasty) end }

Thanks,
-- Max
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[NTG-context] Re: Different behavior of \clf_lastypos vs \clf_lastxpos

[Hans Hagen]

On 9/17/2023 3:26 AM, Aditya Mahajan wrote:
> Hi,
> 
> I am trying to debug an unexpected behavior with tikz reported on tex.se: https://tex.stackexchange.com/q/696136/323
> 
> The attached file shows what is going wrong (without using tikz). For some reason, there is an extra \relax written to file after `\the\numexp\clf_lastypos\relax` (there is no such relax after `\the\numexpr\clf_lastxpos\relax`). The test.pgf file is:
> 
>    \macro {A}{23930350}{43358454.0\relax }
>    \macro {B}{39564274.0\relax }{14083538}
> 
> Any ideas on why is the extra \relax written after lastypos and how to fix that?
i'll round the values

wrt relaxes, these can creep in as side effect of tex pushing back 
looked-ahead and not used tokens (there are wasy around this but it's 
not relevant here)

Hans

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

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[NTG-context] Re: Different behavior of \clf_lastypos vs \clf_lastxpos

[Hans Hagen]

On 9/17/2023 9:04 AM, Max Chernoff wrote:
> Hi Aditya,
> 
>> For some reason, there is an extra \relax written to file after
>> `\the\numexp\clf_lastypos\relax` (there is no such relax after
>> `\the\numexpr\clf_lastxpos\relax`). The test.pgf file is:
>>
>> \macro {A}{23930350}{43358454.0\relax } \macro {B}{39564274.0\relax
>>    }{14083538}
>>
>> Any ideas on why is the extra \relax written after lastypos and how to
>> fix that?
> 
> \numexpr stops at the first non-expandable or non-digit token. If
> \clf_last[xy]pos expands to an integer, then that's the \relax, but if
> it expands to a float, then that's the decimal point.
> 
> With Lua, adding, subtracting, or multiplying two integers will give you
> an integer, but dividing gives you a float. So somewhere in the backend,
> the vertical position is probably divided but the horizontal position is
> only added or subtracted.
> 
> To fix this, change lines 2344--2345 of anch-pos.lmt from
> 
>     implement { name = "lastxpos", actions = function() context(jobpositions.lastx) end }
>     implement { name = "lastypos", actions = function() context(jobpositions.lasty) end }
> 
> to
> 
>     implement { name = "lastxpos", actions = function() context("%.0f", jobpositions.lastx) end }
>     implement { name = "lastypos", actions = function() context("%.0f", jobpositions.lasty) end }

it's better to do some rounding earlier on

Hans


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

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