# Question:why has works different on seemingly same input?

## Question:why has works different on seemingly same input?

Maple 2023

I obtained a Plot p, then trying to find if it has Float(undefined) in it. I am basically trying to find if DEplot returns an empty plot or not. I found that it the plot structure has HFlat(undefined) then this seems to imply an empty plot. So I said, then in the code I can check for HFlat(undefined) in the plot and it is there, then I know the plot is empty.

But this check is not working.

I used has(....,Float(undefined)) and this returns false. But if I copy and paste part of the plot structure and try the check on the copy, it gives true.

I do not understand what is the difference. First here is screen shot, and below if complete code to reproduce.

```restart;
ode2:=2*y(t)+t*diff(y(t),t) = t^2-t+1;

p:=DEtools:-DEplot(ode2,y(t),t=0..3.5,y=0..3,
linecolor = red,
arrowsize ='magnitude',
numpoints = 200 ,
axes = boxed,color = ('magnitude[legacy]')):

p0:=Array(1 .. 3,1 .. 2,{(1, 1) = HFloat(undefined), (1, 2) = HFloat(undefined), (2
, 1) = HFloat(undefined), (2, 2) = HFloat(undefined), (3, 1) = HFloat(undefined
), (3, 2) = HFloat(undefined)},datatype = float[8],order = C_order);
whattype(p0);
has(p0,HFloat(undefined))

p1:=op([1,2],p);
whattype(p1);
has(p1,HFloat(undefined))

```

Worksheet attached also.

Maple 2023.2 on windows 10

 > restart;

 > ode2:=2*y(t)+t*diff(y(t),t) = t^2-t+1; p:=DEtools:-DEplot(ode2,y(t),t=0..3.5,y=0..3,                         linecolor = red,                                                 arrowsize ='magnitude',                         numpoints = 200 ,                         axes = boxed,color = ('magnitude[legacy]')):

 > p0:=Array(1 .. 3,1 .. 2,{(1, 1) = HFloat(undefined), (1, 2) = HFloat(undefined), (2 , 1) = HFloat(undefined), (2, 2) = HFloat(undefined), (3, 1) = HFloat(undefined ), (3, 2) = HFloat(undefined)},datatype = float[8],order = C_order); whattype(p0); has(p0,HFloat(undefined))

 > p1:=op([1,2],p); whattype(p1); has(p1,HFloat(undefined))

 >

question is: Why the above give different result? And what is the correct way to check if the output plot from DEplot is empty or not (in code)?