Parse nan and inf into numbers

[drhagenabm]

Langium has the ability to parse strings into numbers so that not all attributes need to be strings. This also works on "NaN" and "Infinity". Is there a way to parse strings other than "NaN" and "Infinity" into numbers? I mean, terminal NAN returns number: 'nan'; works for funny reasons, but terminal INFINITY returns number: 'inf'; does not.

For example, this grammar parsers "inf" as NaN:

grammar HelloWorld

entry Model:
    (number+=FloatLiteral)*;

FloatLiteral:
    value=FLOAT;

terminal FINITE_FLOAT returns number: /\d+((\.\d+([Ee][+-]?\d+)?)|((\.\d+)?[Ee][+-]?\d+))/;
terminal NAN returns number: 'nan';
terminal INFINITY returns number: 'inf';
FLOAT returns number:
    NAN | INFINITY | FINITE_FLOAT;

hidden terminal WS: /\s+/;
terminal ID: /[_a-zA-Z][\w_]*/;

hidden terminal ML_COMMENT: /\/\*[\s\S]*?\*\//;
hidden terminal SL_COMMENT: /\/\/[^\n\r]*/;

[msujew]

Hey @drhagenabm,

the value conversion for terminals and data type rules happens in the ValueConverter. By default, it will just use Number('input') to convert to a number. You can override the service to adjust the behavior.