SWI-Prolog -- (is)/2

Documentation
- Reference manual
  - Built-in Predicates
    - Arithmetic
      - General purpose arithmetic
        
        >/2
        
        </2
        
        =</2
        
        >=/2
        
        =\=/2
        
        =:=/2
        
        is/2
        
        Arithmetic types
        
        Rational number examples
        
        Arithmetic Functions
- Packages

Availability:built-in

[ISO]-Number is +Expr

True when Number is the value to which Expr evaluates. Typically, is/2 should be used with unbound left operand. If equality is to be tested, =:=/2 should be used. For example:

`?- 1 is sin(pi/2).`	Fails! sin(pi/2) evaluates to the float 1.0, which does not unify with the integer 1.
`?- 1 =:= sin(pi/2).`	Succeeds as expected.