I want to combine two `ifdefined` statements as a single one.

```
\ifdefined\A
    blablablablablabla
\fi

\ifdefined\B
    blablablablablabla
\fi

```

Then, how to combine these two as

```
\ifdefined\(A & B) % this macro is not correct
    blablablablablabla
\fi

```

or

```
\ifdefined\(A or B) % this macro is not correct
    blablablablablabla
\fi

```

Any idea about this?