Subs function invalid operand message

Hello all,

I'm trying to evaluate several boolean expressions which involves symbolic variables D and R.

When I try to evaluate

f3 = ~R & ~D 
R = 0; D = 0;
subs(f3)
ans =
~0

it works fine.

But for some reason, several expressions occur "Invalid operand" error message.

For example:

f3 = ~D & R 
R = 0; D = 0;
subs(f3)
Error using symengine
Invalid operand.
Error in sym/subs>mupadsubs (line 160)
G = mupadmex('symobj::fullsubs',F.s,X2,Y2);
Error in sym/subs (line 145)
    G = mupadsubs(F,X,Y); 

However, if I try to evaluate the expression above without symbolic variables:

~0 & 0
ans =
  logical
   0

it works perfectly.

Any suggestions how to solve this issue?

Thanks in advance.

[madhan ravi]

why do you convert it to symbolic variable ?

[or ohev shalom]

Do you mean in the first place?

Because the expressions are built in a for loop, each time a different expression..

[madhan ravi]

subs(f3,{R,D},{0,0})

[or ohev shalom]

Gives the same expression without evaluation...

temp = subs(f3,{R,D},{0,0})
temp =
~D & R

[madhan ravi]

What does the below show? , when you type it in command window

whos R
whos D

[or ohev shalom]

Correction:

If R and D are symbolic then

subs(f3,{R,D},{0,0})

gives the same error.

If R and D are changed to logical\double (after building the expression) then I get

temp = subs(f3,{R,D},{0,0})
temp =
~D & R