70 | SYNTAX DIRECTED TRANSLATION SDT part 2 | Compiler Design
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Syntax-directed translation refers to a method of compiler implementation where the source language translation is completely driven by the parser. A common method of syntax-directed translation is translating a string into a sequence of actions by attaching one such action to each rule of a grammar.
Parser uses a CFG (Context-free-Grammer) to validate the input string and produce output for next phase of the compiler. Output could be either a parse tree or abstract syntax tree. Now to interleave semantic analysis with syntax analysis phase of the compiler, we use Syntax Directed Translation.
Definition
Syntax Directed Translation are augmented rules to the grammar that facilitate semantic analysis. SDT involves passing information bottom-up and/or top-down the parse tree in form of attributes attached to the nodes. Syntax directed translation rules use 1) lexical values of nodes, 2) constants & 3) attributes associated to the non-terminals in their definitions.
The general approach to Syntax-Directed Translation is to construct a parse tree or syntax tree and compute the values of attributes at the nodes of the tree by visiting them in some order. In many cases, translation can be done during parsing without building an explicit tree.