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54 lines
1.4 KiB
Markdown
54 lines
1.4 KiB
Markdown
## Initial Grammar (Left recursivity)
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This grammar is conceived to take into account both left associativity
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and priority of operators to wit () is of highest priority followed by |
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and then || and && which share the same priority (priorization therefore
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occurs because of left associativity).
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```
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LINE -> CMDS eol
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CMDS -> CMDS LIST_OP PIPELINE
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CMDS -> PIPELINE
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PIPELINE -> PIPELINE | GROUP_OR_SIMPLE
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PIPELINE -> GROUP_OR_SIMPLE
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GROUP_OR_SIMPLE -> (CMDS) REDIR
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GROUP_OR_SIMPLE -> SIMPLE
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SIMPLE -> REDIR word REDIR SIMPLE_LST
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SIMPLE_LST -> word REDIR SIMPLE_LST
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SIMPLE_LST -> ε
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REDIR -> > word REDIR
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REDIR -> >> word REDIR
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REDIR -> < word REDIR
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REDIR -> << word REDIR
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REDIR -> ε
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LIST_OP -> &&
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LIST_OP -> ||
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```
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## Grammar after removal of left recursivity
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The same priorities as the previous version except it is now LL(1) and
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therefore compatible with descending syntax analysis (LL(1)).
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```
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LINE -> CMDS eol
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CMDS -> PIPELINE OPT_CMDS
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OPT_CMDS -> LIST_OP PIPELINE OPT_CMDS
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OPT_CMDS -> ε
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PIPELINE -> GROUP_OR_SIMPLE OPT_PIPELINE
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OPT_PIPELINE -> | GROUP_OR_SIMPLE OPT_PIPELINE
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OPT_PIPELINE -> ε
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GROUP_OR_SIMPLE -> (CMDS) REDIR
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GROUP_OR_SIMPLE -> SIMPLE
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SIMPLE -> REDIR SIMPLE_TAIL
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SIMPLE_TAIL -> word REDIR SIMPLE_TAIL
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SIMPLE_TAIL -> ε
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REDIR -> > word REDIR
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REDIR -> >> word REDIR
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REDIR -> < word REDIR
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REDIR -> << word REDIR
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REDIR -> ε
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LIST_OP -> &&
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LIST_OP -> ||
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```
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