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| <div style="text-align: center;"> <big><big><span |
| style="font-weight: bold;">DParser FAQ<br> |
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| <div style="text-align: left;"><big><br> |
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| style="font-weight: bold;"><span style="font-weight: bold;">1. How do |
| I access the subnodes for expressions like "S: A*;" ?<br> |
| <span style="font-weight: bold;"><span style="font-weight: bold;"><span |
| style="font-weight: bold;"><br> |
| </span></span></span></span></span>In this case, "A*" is $n0 of type |
| D_ParseNode. In dparse.h the functions |
| d_get_number_of_children(D_ParseNode *) and d_get_child(D_ParseNode *, |
| int) allow you to get the number of children (<span |
| style="font-weight: bold;">A</span>'s) by calling |
| d_get_number_of_children(&$n0) and individual children by calling |
| d_get_child(&$n0, x).<br> |
| <br> |
| See the example: tests/g27.test.g<br> |
| <span style="font-weight: bold;"><br> |
| <span style="font-weight: bold;">2. Why doesn't '$n0.end_skip' include |
| the trailing whitespace when $n0 is a string/regex?<br> |
| <br> |
| </span></span>Whitespace is not skipped as part of the scan of a |
| string/regex but is done later (when the new parse state is |
| created). This makes it possible to change the whitespace parser |
| as a result of recognition of a particular string/regex. This is |
| used in the python grammar to handle implicit line joining.<br> |
| <br> |
| See the regex-productions LP RP LB RB LC RC in test/python.test.g.<br> |
| <br> |
| <span style="font-weight: bold;">3. What is the difference between |
| DParser and ANTLR?<br> |
| <span style="font-weight: bold;"></span></span><br> |
| The basic syntax of DParser and ANTLR grammars is very similar. |
| In fact, the DParser example ANSI-C grammar was ported from ANTLR in |
| less than an hour. <br> |
| <br> |
| Beyond that there are a number of differences. First of all ANTRL |
| has been developed for over a decade while DParser is relatively |
| young. Internally, DParser is a table-driven parser while ANTLR |
| generates directly executable parsers. DParser is a GLR parser |
| based on the Tomita algorithm while ANTLR is modified LL(k). |
| DParser is scannerless while ANTLR uses token streams. In terms |
| of power, both DParser and ANTLR are very powerful. In theory |
| DParser can handle any context free grammar, though not necessarily in |
| linear time. In practice ANTLR is likely to be faster (mostly |
| because it is more mature). Beyond that you would really |
| have ask Terance Parr who is more of a hard core parsing theory guru |
| than I am.<br> |
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