I’ve plowed through the TODO list. It feels good to have all those little issues cleaned up. I’ve also got the E, D, F, and G format specifiers working, and mostly (I think) compliant with the spec. Eventually I’ll get this thing to the point where I can run the NIST Fortran 77 test suite, and then I’ll find out for sure. I expect that I’ll be non-compliant in enough areas that just getting the tests to run at all will be difficult, but we’ll see.
I also got a little bit more done on the FORMAT statement, which now accepts the F (fixed), E (exponential), D (alias for E), G (fixed/exponential, depending), a L (logical) edit descriptors:
PRINT 30, 123.456, 123.456, -123.456
30 FORMAT (F8.3, E12.3, D12.3)
PRINT 40, 0.1234, 0.1234E10
40 FORMAT (G14.4)
PRINT 50, .TRUE., .FALSE.
50 FORMAT (L2)
END 123.456 0.123E+03 -0.123E+03
0.1234
0.1234E+10
T
F
I want to go finish all of the other edit descriptors, but there’s a problem I can’t ignore anymore: the parser’s error reporting stinks. I could explain it in all it’s gory details, but I’ll just show you the horror of it. Here’s a short program with an erroneous trailing comma in the last PRINT statement:
PRINT *, 'a', 'bc'
PRINT *
PRINT *, 'def',
ENDAnd the actual error message this generates:
Expected /\Z/ at " PRINT *, 'a', 'bc'\n PRINT *\n PRINT *, 'def',\n END\n"
Basically, all you get is what string or regex was expected, and what is left of the program, as one big string. Because of backtracking, the parser basically ends up telling you, “This doesn’t match a program. Since it doesn’t match a program, I expected the end of the file, but instead found this program. I tried a whole bunch of stuff, which I’ve forgotten about so I can’t tell you. You’ll have to figure it out.”
Nice, huh?
So now I’ve got to figure out how to get decent error reporting cooked into this parser. I’ve been putting it off because I have only a vague idea how to go about it. I can’t put it off any longer.