I believe I've tracked down the bug with For( loops being very slow when the first line is a lone If block with a false condition and there's no ) or newline between the For( and the If.

It's complicated and hard to explain, but basically the code that handles the For( token assumes that you've put the ) on the end of the For( line, and so when it executes the For block, instead of jumping to the start of the line containing the If, it jumps to the If token itself.

Normally this isn't a problem, but it's important for the parser to handle the start of the line because it removes a byte from the operator stack that always gets pushed when beginning parsing of the line. Because an If block with a false condition will jump over the next line (including the newline), this never gets canceled out at the beginning of the loop, and so with every iteration you lose bytes of the operator stack. This in turn causes memory leaks and confuses the parser about what temporary variables should be cleaned up, and it's forced to near-constantly "garbage collect".

Or at least that's my theory.

In any case, the For( code shouldn't be making that stupid assumption, so I patched my OS to see if I could fix it, and it appears successful. I uploaded it to http://brandonw.net/crap/84P_OS2.41_BASICFixed.8xu if anyone wants to try it.

So we could be happy with this, or we could write an oncalc patch that does this in an OS version-independent way, or we could just live with the fact that you need a ).

Thoughts?