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Expression Abstracts

Expression abstracts = functions.

D ::= ...| fcn I=E
E ::= E₁+E₂ | ...| I

• Constant definition.

  Environment and store are bound at point of definition.

• Function definition.

  Only environment is bound at point of definition, store is supplied at invocation-time.

• Macro definition.

  Both environment and store are supplied at invocation-time.

Constants, functions, macros are variations of the same mechanism!