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examples: add an example with a reentrant parser in Flex+Bison

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Suggested by Eric S. Raymond.
https://lists.gnu.org/archive/html/bison-patches/2019-02/msg00066.html

* examples/c/reentrant-calc/Makefile, examples/c/reentrant-calc/README.md,
* examples/c/reentrant-calc/parse.y, examples/c/reentrant-calc/scan.l
* examples/c/reentrant-calc/lexcalc.test,
* examples/c/reentrant-calc/local.mk:
New.
This commit is contained in:
Akim Demaille
2019-02-16 13:13:30 +01:00
parent 0adda755a2
commit 6289d673a0
15 changed files with 845 additions and 3 deletions
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14
examples/c/README.md
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@@ -2,7 +2,7 @@
This directory contains simple examples of Bison grammar files in C.
Most of them come from the documentation, which should be installed together
Some of them come from the documentation, which should be installed together
with Bison. The URLs are provided for convenience.
## rpcalc - Reverse Polish Notation Calculator
@@ -16,7 +16,7 @@ https://www.gnu.org/software/bison/manual/html_node/RPN-Calc.html
## calc - Simple Calculator
This example is slightly more complex than rpcalc: it features infix
operators (`1 + 2`, instead of `1 2 +` in rpcalc), but it does so using a
unambiguous grammar of the arithmetics instead of using precedence
unambiguous grammar of the arithmetic instead of using precedence
directives (%left, etc.).
## mfcalc - Multi-Function Calculator
@@ -30,6 +30,13 @@ https://www.gnu.org/software/bison/manual/html_node/Multi_002dfunction-Calc.html
## lexcalc - calculator with Flex and Bison
The calculator, redux. This time using a scanner generated by Flex.
## reccalc - recursive calculator with Flex and Bison
The example builds on top of the previous one to provide a reentrant parser.
Such parsers can be called concurrently in different threads, or even
recursively. To demonstrate this feature, expressions in parentheses are
tokenized as strings, and then recursively parsed from the parser. So
`(((1)+(2))*((3)+(4)))` uses eight parsers, with a depth of four.
<!---
@@ -47,5 +54,6 @@ Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the "GNU Free
Documentation License" file as part of this distribution.
# LocalWords: mfcalc calc parsers yy
# LocalWords: mfcalc calc parsers yy rpcalc lexcalc redux reccalc ispell
# LocalWords: reentrant tokenized american postfix
--->