Need help in converting passive voice to active voice
Solution 1:
The passive voice without an agent is normally used when the real subject is unknown or unimportant, as shown by OP's examples (1) and (2).
The only possible way in which those two sentences can be turned into the active form consists of using an impersonal subject like "one", "you" or "we":
- A Struct's member can't be defined as abstract, virtual or protected.
1a. One can't define a Struct's member as abstract, virtual or protected.
1b. You can't define a Struct's member as abstract, virtual or protected.
1c. We can't define a Struct's member as abstract, virtual or protected.
With (2) in the present simple, conversion to the active voice does not seem so natural. The most acceptable form, in my opinion, would be rendered by the use of "we":
- It is also called as Rectangular Arrays.
2a. We also call it Rectangular Arrays.