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Add an example to demonstrate the use of push parser. I'm pleasantly surprised: parse.error=detailed works like a charm with push parsers. * examples/c/local.mk, examples/c/pushcalc/Makefile * examples/c/pushcalc/README.md, examples/c/pushcalc/calc.test, * examples/c/pushcalc/calc.y, examples/c/pushcalc/local.mk: New.
71 lines
2.8 KiB
Markdown
71 lines
2.8 KiB
Markdown
# Examples in C
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This directory contains simple examples of Bison grammar files in C.
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Some of them come from the documentation, which should be installed together
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with Bison. The URLs are provided for convenience.
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## rpcalc - Reverse Polish Notation Calculator
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The first example is that of a simple double-precision Reverse Polish
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Notation calculator (a calculator using postfix operators). This example
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provides a good starting point, since operator precedence is not an issue.
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Extracted from the documentation: "Reverse Polish Notation Calculator"
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https://www.gnu.org/software/bison/manual/html_node/RPN-Calc.html
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## calc - Simple Calculator
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This example is slightly more complex than rpcalc: it features infix
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operators (`1 + 2`, instead of `1 2 +` in rpcalc), but it does so using a
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unambiguous grammar of the arithmetic instead of using precedence
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directives (%left, etc.).
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## mfcalc - Multi-Function Calculator
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A more complete C example: a multi-function calculator. More complex than
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the previous example. Using precedence directives to support infix
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operators.
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Extracted from the documentation: "Multi-Function Calculator: mfcalc".
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https://www.gnu.org/software/bison/manual/html_node/Multi_002dfunction-Calc.html
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## lexcalc - calculator with Flex and Bison
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The calculator, redux. This time using a scanner generated by Flex.
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## reccalc - recursive calculator with Flex and Bison
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The example builds on top of the previous one to provide a reentrant parser.
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Such parsers can be called concurrently in different threads, or even
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recursively. To demonstrate this feature, expressions in parentheses are
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tokenized as strings, and then recursively parsed from the parser. So
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`(((1)+(2))*((3)+(4)))` uses eight parsers, with a depth of four.
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## pushcalc - calculator implemented with a push parser
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All the previous examples are so called "pull parsers": the user invokes the
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parser once, which repeatedly calls the scanner until the input is drained.
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This example demonstrates the "push parsers": the user calls the scanner to
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fetch the next token, passes it to the parser, and repeats the operation
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until the input is drained.
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This example is a straightforward conversion of the 'calc' example to the
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push-parser model.
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<!---
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Local Variables:
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fill-column: 76
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ispell-dictionary: "american"
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End:
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Copyright (C) 2018-2020 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
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Texts. A copy of the license is included in the "GNU Free
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Documentation License" file as part of this distribution.
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# LocalWords: mfcalc calc parsers yy rpcalc lexcalc redux reccalc ispell
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# LocalWords: reentrant tokenized american postfix
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--->
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