NoPrint -- top level method for non-printing results

• Usage:

  X#{topLevelMode,NoPrint} = f

• Inputs:
  • X, a type
  • f, a function, that can accept something of type X
• Consequences:

  • At top level, whenever it is time, as indicated by a semicolon at the end of an input line, to suppress printing of an output value of type X, the function f will be called.