DYPGEN

dypgen provides management of local and global immutable data. The user actions can access it and return it modified. These mechanisms adress the problem posed by global mutable data with GLR parsing and let the user controls the scope of the data. Modifications of local data are preserved when traveling from right to left in a rule or when going down in the parse tree. Modifications of global data are preserved across the complete traversal of the parse tree. These data may be used for instance to do type-checking at parsing time in an elegant and acceptable way. The local data may contain the environment that associates a type to each variable while the global data would contain the substitution over types that is usually produced by unification.