atan2() Storing symbolic expression into numeric only vector object *Error*

[Magnus512]

Hi there, I'm making my own program to change between coordinate systems:
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EXPORT SPHERE;
//Rectangular to Spherical
//(x,y,z)-->(ρ,θ,φ)
EXPORT RECT2SPHE(CORD)
BEGIN
//Separacion de coordenadas en x,y y z.
LOCAL x:=CORD(1),y:=CORD(2),z:=CORD(3);
//Variables para guardar resultado temporal
LOCAL ρ:=0,θ:=0,φ:=0;
//Operaciones para convertir los valores
ρ:=SQRT((x)^2+(y)^2+(z)^2);
θ:=atan(y/x);
φ:=ACOS(z/ρ);
//Guardar el resultado en la variable global SPHERE
SPHERE:=[ρ,θ,φ];
RETURN("ρ="+ρ+" θ="+θ+" φ="+φ);
END;
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This is a part of the code, but I have some torubles here, when I store the results into SPHERE variable using atan to get the angle (θ:=atan(y/x)) it works just perfect, but if I try to use atan2(y,x) I get this message
   
The error comes out when I use radian mode, but it works in degrees.