about a MSXBASIC compiler?

thx Vincent/Trebint/Vampier i will look at this material soon. I think would be fine to have a basic to 'c' converter also.
Actually i'm faced with the for next basic loops, because of it's implementation in msxbasic i cannot easily directly translate them into 'c' for loop. Most probably i need a more run-time management of for next.
aND a question: anyone think is too much limitative the requirement of having explicitly declared the variable in the next part?

NEXT : REM WRONG! does not compile
NEXT MYVAR% : OK, because of the MYVAR% declaration.

allowing the latter will improve performaces...

Haven't worked with MSXBasic for a long time, but shouldn't for next loops always be nested? I don't think it would work correctly if you did something like

for a=1 to 3 step 2
for b=3 to 1 step -1
next a
next b

I think you need to use a stack for the FOR statements. Then when you call NEXT you'll go from the top of the stack to the bottom and search for a match to the argument of the NEXT statement.
When you find a match you'll just discard any more recent entries in the stack.

For example if you do:

10 FORI=1TO5
20 FORJ=1TO10
30 PRINTJ;
40 IFJ=2THENNEXTIELSENEXT
50 NEXTJ

This program will (I think) print:

1212121212

and get a NEXT without FOR error on line 50 because the FORJ is removed from the FOR stack by the NEXTI call

dvik: nothing personal, but this way of BASIC coding stinks. Breaking from [nested] loops is considered a sin in computer science . But you probably know that already. Should anyone write a compiler, I'd opt it would only parse 100% legal code. Bit like XML, where you must have proper closing of elements.

Here is another example that makes it a bit more tricky:

10 FOR I=1 TO 5
20 PRINT I
30 GOSUB 100
40 END
100 NEXT I

In this case you'll get a "NEXT without FOR in 100" error so the NEXT I will not be matched with the FOR I statement.
The reason is that the GOSUB call is also placed on the stack and the NEXT I search goes back only to the GOSUB entry on the stack.

And the RETURN statement of a GOSUB routine will remove any active FOR loops within the sub routine. So in the example below the NEXT statement on line 30 will not match to the FOR J statement because the FOR J is removed from the stack by the RETURN call:

10 FOR I=0 TO 5
20 GOSUB 100
30 NEXT
40 END
100 FOR J=0 TO 10
110 PRINT J;
120 RETURN

Outputs: 11111

But one thing is funny though. Since all variables are global the following program:

10 FOR I=1 TO 5
20 GOSUB 100
30 NEXT I
100 FOR I=1 TO 2
110 PRINT I;
120 NEXT I
130 RETURN

will output: 1212121212121212121212121212121212......