From: Keith McKay <mckaymeister@gmail.com>
To: mailing list for ConTeXt users <ntg-context@ntg.nl>
Subject: Arithmetic Overflow error in MetaFun
Date: Sat, 16 May 2020 15:36:10 +0100 [thread overview]
Message-ID: <4830f0a0-ece9-53ce-2768-af9110f3962a@gmail.com> (raw)
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Colleagues
I'm having problems with an Arithmetic Overflow error when calculating
the x and y values for functions of the form:
y = ax^4 + bx^3 + cx^2 + dx + e
to which I then add a bit of randomness and other embellishments. I have
had a look in the Metafun and Metafont manuals but nothing jumps out at
me. In the minimum working example below, this Arithmetic Overflow
occurs when xord =13.5 but I can get the calculation to work if I
separate out the equation and then add together, since it seems to be
failing on the pow(xord,4) instruction. Is there a switch in MetaFont
that should be set or a better way of getting round this Arithmetic
Overflow error?
Thanks
Best Wishes
Keith McKay
%%%%%%%%%%%%%MWE%%%%%%%%%%%
\setuppapersize [A4,landscape]
\starttext
\startMPpage
StartPage;
width := PaperWidth ; height := PaperHeight ; unit := cm ;
path p;
p := unitsquare scaled .1cm ;
path pat;
pat := (0.0*cm,19.935*cm);
for xord = 0 step 0.1 until 25:
show xord;
%%%%%%%%fails at xord = 13.5%%%%%%%%%
yord := ((-0.000268117) * pow(xord,4)) +(0.0136949 * pow(xord, 3)) +
((-0.16608) * sqr(xord)) + ((-0.771743) * xord) + 19.935;
%%%%%comment out above and uncomment below and it works%%%%
% yord1 := (-0.000268117) * sqr(xord);
% yord1a := yord1 * sqr(xord);
% yord2 := (0.0136949 * pow(xord, 3));
% yord3 := ((-0.16608) * sqr(xord));
% yord4 := ((-0.771743) * xord);
% yord := yord1 + yord1a + yord2 + yord3 + yord4 + 19.935;
xrand := (uniformdeviate(1) - 0.5)*2;
yrand := uniformdeviate(1) - 0.5;
xcoord := xord + xrand;
ycoord := yord + yrand;
if odd xord:
pat := pat ... (xcoord*cm, ycoord*cm);
else:
pat := pat --- (xcoord*cm, ycoord*cm);
fill p shifted (xcoord*cm, ycoord*cm) withcolor
(uniformdeviate(1),uniformdeviate(1),uniformdeviate(1)) ;
fi;
draw pat withpen pencircle scaled (uniformdeviate(0.75)*mm) withcolor
(uniformdeviate(1),uniformdeviate(1),uniformdeviate(1));
%withtransparency (1, .5);
drawdot (xcoord*cm, ycoord*cm) withpen pencircle scaled
(uniformdeviate(2.5)*mm) withcolor
(uniformdeviate(1),uniformdeviate(1),uniformdeviate(1));
endfor;
StopPage;
\stopMPpage
\stoptext
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next reply other threads:[~2020-05-16 14:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-16 14:36 Keith McKay [this message]
2020-05-16 14:48 ` Keith McKay
2020-05-16 19:46 ` Hans Hagen
2020-05-17 8:19 ` Keith McKay
2020-05-16 14:50 ` Hans Hagen
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