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1 yply.py
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2
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3 This example implements a program yply.py that converts a UNIX-yacc
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4 specification file into a PLY-compatible program. To use, simply
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5 run it like this:
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6
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7 % python yply.py [-nocode] inputfile.y >myparser.py
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8
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9 The output of this program is Python code. In the output,
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10 any C code in the original file is included, but is commented out.
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11 If you use the -nocode option, then all of the C code in the
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12 original file is just discarded.
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13
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14 To use the resulting grammer with PLY, you'll need to edit the
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15 myparser.py file. Within this file, some stub code is included that
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16 can be used to test the construction of the parsing tables. However,
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17 you'll need to do more editing to make a workable parser.
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18
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19 Disclaimer: This just an example I threw together in an afternoon.
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20 It might have some bugs. However, it worked when I tried it on
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21 a yacc-specified C++ parser containing 442 rules and 855 parsing
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22 states.
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23
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24 Comments:
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25
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26 1. This example does not parse specification files meant for lex/flex.
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27 You'll need to specify the tokenizer on your own.
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28
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29 2. This example shows a number of interesting PLY features including
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30
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31 - Parsing of literal text delimited by nested parentheses
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32 - Some interaction between the parser and the lexer.
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33 - Use of literals in the grammar specification
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34 - One pass compilation. The program just emits the result,
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35 there is no intermediate parse tree.
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36
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37 3. This program could probably be cleaned up and enhanced a lot.
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38 It would be great if someone wanted to work on this (hint).
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39
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40 -Dave
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