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Defining Language Semantics
The grammar rules for a language determine only the syntax. The
semantics are determined by the semantic values associated with various
tokens and groupings, and by the actions taken when various groupings
For example, the calculator calculates properly because the value
associated with each expression is the proper number; it adds properly
because the action for the grouping `X + Y' is to add the numbers
associated with X and Y.
- Value Type
- Specifying one data type for all semantic values.
- Multiple Types
- Specifying several alternative data types.
- An action is the semantic definition of a grammar rule.
- Action Types
- Specifying data types for actions to operate on.
- Mid-Rule Actions
- Most actions go at the end of a rule.
This says when, why and how to use the exceptional
action in the middle of a rule.
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