Jelly, 5 bytes

VeMḂ$

Try it online!

Monadic function expecting a string. Inputs with leading !s cause a 1 to be printed to STDOUT along the way, so the TIO link I give is a test harness that prints the input-output pairs beneath the first line of output.

###How?

VeMḂ$ - Monadic link: string
V     - eval the string
          - the implicit input of 0 causes !...! to evaluate to 1 (which gets printed),
          - the result is the evaluation of the rest: "0"=0; "0!"=1; "1"=1; "1!"=1; ...
 e    - exists in?
    $ - last two links as a monad:
  M   -     Maximal indexes - the "0" and "1" characters are greater than "!",
                            - so this results in a list of one item [i] where
                            - i is the 1-based index of the 0 or 1 character.
   Ḃ  -     %2 (vectorises) - [i%2], so a 0 if we need to logically negate and a 1 if not
                            - hence we check equality with e rather than inequality.

Jelly, 5 bytes

VeMḂ$

Try it online!

Monadic function expecting a string. Inputs with leading !s cause a 1 to be printed to STDOUT along the way, so the TIO link I give is a test harness that prints the input-output pairs beneath the first line of output.

How?

VeMḂ$ - Monadic link: string
V     - eval the string
          - the implicit input of 0 causes !...! to evaluate to 1 (which gets printed),
          - the result is the evaluation of the rest: "0"=0; "0!"=1; "1"=1; "1!"=1; ...
 e    - exists in?
    $ - last two links as a monad:
  M   -     Maximal indexes - the "0" and "1" characters are greater than "!",
                            - so this results in a list of one item [i] where
                            - i is the 1-based index of the 0 or 1 character.
   Ḃ  -     %2 (vectorises) - [i%2], so a 0 if we need to logically negate and a 1 if not
                            - hence we check equality with e rather than inequality.

Jelly, 5 bytes

VeMḂ$

Try it online!

Monadic function expecting a string. Inputs with leading !s cause a 1 to be printed to STDOUT along the way, so the TIO link I give is a test harness that prints the input-output pairs beneath the first line of output (which has more pollution from this code!).

###How?

VeMḂ$ - Monadic link: string
V     - eval the string
          - the implicit input of 0 causes !...! to evaluate to 1 (which gets printed),
          - the result is the evaluation of the rest: "0"=0; "0!"=1; "1"=1; "1!"=1; ...
 e    - exists in?
    $ - last two links as a monad:
  M   -     Maximal indexes - the "0" and "1" characters are greater than "!",
                            - so this results in a list of one item [i] where
                            - i is the 1-based index of the 0 or 1 character.
   Ḃ  -     %2 (vectorises) - [i%2], so a 0 if we need to logically negate and a 1 if not
                            - hence we check equality with e rather than inequality.

Jelly, 5 bytes

VeMḂ$

Try it online!

Monadic function expecting a string. Inputs with leading !s cause a 1 to be printed to STDOUT along the way, so the TIO link I give is a test harness that prints the input-output pairs beneath the first line of output.

###How?

VeMḂ$ - Monadic link: string
V     - eval the string
          - the implicit input of 0 causes !...! to evaluate to 1 (which gets printed),
          - the result is the evaluation of the rest: "0"=0; "0!"=1; "1"=1; "1!"=1; ...
 e    - exists in?
    $ - last two links as a monad:
  M   -     Maximal indexes - the "0" and "1" characters are greater than "!",
                            - so this results in a list of one item [i] where
                            - i is the 1-based index of the 0 or 1 character.
   Ḃ  -     %2 (vectorises) - [i%2], so a 0 if we need to logically negate and a 1 if not
                            - hence we check equality with e rather than inequality.

Jelly, 5 bytes

VeMḂ$

Try it online!

Jelly, 5 bytes

VeMḂ$

Try it online!

Monadic function expecting a string. Inputs with leading !s cause a 1 to be printed to STDOUT along the way, so the TIO link I give is a test harness that prints the input-output pairs beneath the first line of output (which has more pollution from this code!).

###How?

VeMḂ$ - Monadic link: string
V     - eval the string
          - the implicit input of 0 causes !...! to evaluate to 1 (which gets printed),
          - the result is the evaluation of the rest: "0"=0; "0!"=1; "1"=1; "1!"=1; ...
 e    - exists in?
    $ - last two links as a monad:
  M   -     Maximal indexes - the "0" and "1" characters are greater than "!",
                            - so this results in a list of one item [i] where
                            - i is the 1-based index of the 0 or 1 character.
   Ḃ  -     %2 (vectorises) - [i%2], so a 0 if we need to logically negate and a 1 if not
                            - hence we check equality with e rather than inequality.