NZiffer ::= 1 | ... | 9
Ziffer ::= 0 | NZiffer
Unterstrich ::= _*
NBlock ::= ( 0 | NZiffer (Unterstrich Ziffer)*)
Block ::= Ziffer (Unterstrich Ziffer)*
Exponent ::= (e|E) (+|-)? NBlock
Double ::= (+|-)? (NBlock Exponent | ( (NBlock . Block?| . Block) Exponent?) )