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Updated README

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yhirose 2020-02-07 18:37:14 -05:00
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@ -22,7 +22,9 @@ The PEG syntax is well described on page 2 in the [document](http://www.brynosau
* `$name` (Backreference operator)
* `MACRO_NAME(` ... `)` (Parameterized rule or Macro)
This library also supports the linear-time parsing known as the [*Packrat*](http://pdos.csail.mit.edu/~baford/packrat/thesis/thesis.pdf) parsing.
This library supports the linear-time parsing known as the [*Packrat*](http://pdos.csail.mit.edu/~baford/packrat/thesis/thesis.pdf) parsing.
*Parsing expressions by [Precedence climbing](https://eli.thegreenplace.net/2012/08/02/parsing-expressions-by-precedence-climbing)* algorithm is also supported.
IMPORTANT NOTE for some Linux distributions such as Ubuntu and CentOS: Need `-pthread` option when linking. See [#23](https://github.com/yhirose/cpp-peglib/issues/23#issuecomment-261126127), [#46](https://github.com/yhirose/cpp-peglib/issues/46#issuecomment-417870473) and [#62](https://github.com/yhirose/cpp-peglib/issues/62#issuecomment-492032680).
@ -341,23 +343,23 @@ List(I, D) ← I (D I)*
T(x) ← < x > _
```
Parsing expressions by precedence climbing altorithm
Parsing expressions by Precedence climbing altorithm
----------------------------------------------------
*cpp-peglib* supports [operator-precedence parsering](https://en.wikipedia.org/wiki/Operator-precedence_parser) by [**precedence climbing algorithm**](https://eli.thegreenplace.net/2012/08/02/parsing-expressions-by-precedence-climbing)
```cpp
parser parser(R"(
EXPRESSION <- PRECEDENCE_PARSING(ATOM, OPERATOR)
PRECEDENCE_PARSING(A, O) <- A (O A)* {
precedence
L + -
L * /
}
ATOM <- NUMBER / '(' EXPRESSION ')'
OPERATOR <- < [-+/*] >
NUMBER <- < '-'? [0-9]+ >
%whitespace <- [ \t]*
# Parsing expressions by Precedence climbing altorithm
PRECEDENCE_PARSING(A, O) <- A (O A)* {
precedence
L + -
L * /
}
)");
parser["PRECEDENCE_PARSING"] = [](const SemanticValues& sv) -> long {
@ -385,7 +387,7 @@ assert(val == 9);
*precedence* instruction can be applied only to the following 'list' style rule.
```
R <- A (B A)* {
Rule <- Atom (Operator Atom)* {
precedence
L - +
L / *
@ -393,7 +395,7 @@ R <- A (B A)* {
}
```
*precedence* instruction contains precedence info entries. Each entry starts with *associativity* which is 'L' (left) or 'R' (right), then operator tokens follow. The first entry has the highest order.
*precedence* instruction contains precedence info entries. Each entry starts with *associativity* which is 'L' (left) or 'R' (right), then operator tokens follow. The first entry has the highest order level.
AST generation
--------------
@ -591,6 +593,8 @@ Sample codes
* [Calculator](https://github.com/yhirose/cpp-peglib/blob/master/example/calc.cc)
* [Calculator (with parser operators)](https://github.com/yhirose/cpp-peglib/blob/master/example/calc2.cc)
* [Calculator (AST version)](https://github.com/yhirose/cpp-peglib/blob/master/example/calc3.cc)
* [Calculator (parsing expressions by precedence climbing)](https://github.com/yhirose/cpp-peglib/blob/master/example/calc4.cc)
* [Calculator (AST version and parsing expressions by precedence climbing)](https://github.com/yhirose/cpp-peglib/blob/master/example/calc5.cc)
* [PL/0 language example](https://github.com/yhirose/cpp-peglib/blob/master/pl0/pl0.cc)
* [A tiny PL/0 JIT compiler in less than 700 LOC with LLVM and PEG parser](https://github.com/yhirose/pl0-jit-compiler)
@ -599,11 +603,6 @@ PEG debug
A debug viewer for Parsing Expression Grammars using cpp-peglib by [mqnc](https://github.com/mqnc). Please see [his gihub project page](https://github.com/mqnc/pegdebug) for the detail. You can see a parse result of PL/0 code [here](https://mqnc.github.io/pegdebug/example/output.html).
TODO
----
* Advanced Unicode support ([Unicode regular expressoin](http://www.unicode.org/reports/tr18/))
License
-------