>replacing character with string in-place in std::string takes 400ms
>appending to new std::ostringstream instead of replacing in-place takes 100ms
>same thing but with .append() calls to new string takes 15ms
i guess replacing in-place does some iterator invaidation and inserting and probably lots of memory gets copies there
the 100-15ms difference between streams and just a string is because of virtual calls, probably. didnt know it could make this much of a difference 

 maybe also streams have locales and a bunch of other weird checking stuff so i guess that can be a thing too. i should try making a padded string type this time 

 oh shit im retarded nvm i was only iterating once for the latter two:niggadementia: