Music notation question

[kasavien]

Hi all i wasn't sure where to put this since it's not technology related rather it's music theory related. Specifically if a piece of music is in G Major, so there's only one sharp - F# is it allowed in music notation to put an accidental sharp on any F's in the piece to make it F double sharp, or would you need to use the double sharp symbol.

Thanks

Andy

[Steve B]

F# overrides the inferred F# given by the key signature with F#, the same note.
I reckon to get F##, you need to use double sharp

[TheAnimus]

someone awnsered it like a programmer

[Stringent]

Why not just write it as G?

[kasavien]

I think it's for things like diminished and augmented intervals for example a G# and a D double sharp above it would be and augmented 5th