Originally Savannah bug #6490

The NAG interpreter and the Axiom interpreter do not accept the when and otherwise verbs when defining piecewise functions.

There are no library operations named when

(1) -> ch : Integer -> UnivariatePolynomial(x,FRAC(INT))

ch(0) == 1

ch(1) == x

ch(n) == 2 * x * ch(n-1) - ch(n-2) when n > 1

ch(2)

   There are no library operations named when 
      Use HyperDoc Browse or issue
                                )what op when
      to learn if there is any operation containing " when " in its 
      name.
   Cannot find a definition or applicable library operation named when 
      with argument type(s) 
                                   Integer

      Perhaps you should use "@" to indicate the required return type, 
      or "$" to specify which version of the function you need.
   FriCAS will attempt to step through and interpret the code.

Compiling function ch with type Integer -> UnivariatePolynomial(x,
      Fraction(Integer)) 
   There are no library operations named when 
      Use HyperDoc Browse or issue
                                )what op when
      to learn if there is any operation containing " when " in its 
      name.

   Cannot find a definition or applicable library operation named when 
      with argument type(s) 
                                   Integer

      Perhaps you should use "@" to indicate the required return type, 
      or "$" to specify which version of the function you need.

The parser is broken

is when mentioned in the documentation?