Syntax-Directed Translation
A syntax-directed translator reads input and immediately emits output as it goes. In the following image, we see the one-stage application pipeline. Even though it has few moving parts, we can use this for a surprising number of DSLs.
Syntax-directed translators consist of a grammar (or equivalent hand-built parser) and output actions. For example, here is a rule that translates a scalar multiply, such as a x b, to Java:
| | mult : a=ID 'x' b=ID {System.out.println($a.text+"*"+$b.text);} ; |
Because syntax-directed translators make only one pass through the input, they can’t deal with forward references. For example, ...
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