December 2009
Intermediate to advanced
380 pages
9h 2m
English
Content preview from Language Implementation Patterns
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Constructing ASTs with ANTLR Grammars
To learn about ANTLR’s AST construction mechanism, let’s build ASTs for a simple vector math language with addition, multiplication, and dot product.
To design our grammar, we need to look at some sample sentences. Here are some valid vector math statements:
| | x = 1+2 |
| | y = 1*2+3 |
| | z = [1, 2] + [3, 4] |
| | a = [1, 2] . [3, 4] |
| | b = 3 * [1, 2] |
| | print x+2 |
At the coarsest level, that looks like a series of assignment and print statements. We can express that syntax grammatically as follows:
| IR/Vec/VecMath.g | |
| | statlist : stat+ ; // match multiple statements |
| | stat: ID '=' expr // match an assignment like "x=3+4" |
| | | 'print' expr // match a print statement like "print 4" |
| | ; |
Within the statements, we find various ...
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