4.7.5 The Language structure

fixityInOpen

Compatibility option

Structure

Shell.Options.Language

Type

val fixityInOpen: bool option

Description

If true, allow inclusion of fixity in open. This option considers fixity information given in structures when opened. If this option is not checked when they are defined, structures containing fixity information will be accepted, but the fixity information will not be available when they are opened.

Example

The following structure contains fixity information. In the first case no error occurs:

MLWorks> structure S = struct infix $$$ end;
structure S =
  struct
  end
MLWorks> open S;
MLWorks> val $$$ = 3;
val $$$ : int = 3
MLWorks>

If the fixity information had been recognized when the structure was opened the final expression,

val $$$ =3;

would have raised an error, as there was no op preceding the $$$ to show that it was not a reference to the operator with the same name. With fixityInOpen set to true, the fixity information in the structure is used:

MLWorks> set (fixityInOPen, true);
val it : unit = ()
MLWorks> structure S = struct infix $$$ end;
structure S =
  struct
  end
MLWorks> open S;
infix 0 $$$
MLWorks> val $$$ = 3;
MLWorks>

An error browser with the message "Reserved word 'op' required before infix identifier '$$$'" appears.