numSyntax.is

An invocation is_numeral tm, where tm is a HOL term with the following form

     <numeral> ::= 0 | NUMERAL <bits>
     <bits>    ::= ZERO | BIT1 (<bits>) | BIT2 (<bits>)

returns true; otherwise, false is returned. The NUMERAL constant is used as a tag signalling that its argument is indeed a numeric literal. The ZERO constant is equal to 0, and BIT1(n) = 2*n + 1 while BIT2(n) = 2*n + 2. This representation allows asymptotically efficient operations on numeric values.

The system prettyprinter will print a numeral as a string of digits.