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Name Equivalence

• Complicated in practice:
  • Primitive types (intloc) are always treated equivalent (named by class definition or not).
  • Each occurence of compound type structures (array, record) is treated as new type (whether named or not).
• Supports "encapsulation"
  • Procedures parameterized on one type of record structure cannot be abused by giving another.
  • record x: newreal; y: newreal end
    record r: newreal; phi: newreal end
• Straight-forward to implement.
  • Attach unique integer tag to each compound type-structure expression.
• Less natural logic.
  • No basic problem.
  • Just fewer programs well-typed.