Decimal floating-point literal syntax

1+ 
1? digit
1.1 .
1.2+ 
1.2 digit
1.2.1? %exponent
1+ 
1 digit
1.1 .
1.2? %exponent
1+ 
1 digit
1.1 %exponent
2 df
2 DF
2 dd
2 DD
2 dl
2 DL

Exponent:

1 e
1 E
2? 
2 +
2  -
3+ 
3 digit