[NTG-context] atan2 function
Thangalin
thangalin at gmail.com
Thu Oct 13 07:40:59 CEST 2022
Hi there,
How is atan2 called? I rolled my own as follows:
% SOT
\startuseMPgraphic{HexGridBaseGraphic}
vardef atantwo( expr ax, ay, bx, by ) =
save theta;
numeric dx;
numeric dy;
numeric theta;
dx := bx - ax;
dy := by - ay;
theta := 0;
if (dx > 0):
theta := atan( dy / dx );
elseif (dx < 0) and (dy >= 0):
theta := atan( dy / dx ) + pi;
elseif (dx < 0) and (dy < 0):
theta := atan( dy / dx ) - pi;
elseif (dx == 0) and (dy > 0):
theta := pi / 2;
elseif (dx == 0) and (dy < 0):
theta := -pi / 2;
fi;
%theta := atan( dy, dx );
theta
enddef;
% EOT
When this runs, the expected result is generated:
https://pdfhost.io/v/xdNxANU18_scaled
When uncommenting "atan( dy, dx )", an unexpected result is generated:
https://pdfhost.io/v/QdfU89IL._scaled
Is atan with two parameters supposed to behave like atan2?
Cheers!
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