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Add subscript operator to Expression to access sub-expressions by name #60

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merged 6 commits into from
Feb 5, 2021
Merged

Add subscript operator to Expression to access sub-expressions by name #60

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20acdc0
Add another subscript operator to expression to access sub-expression…
jteuber Feb 2, 2021
a7e9c07
explicitly include optional for windows.
jteuber Feb 3, 2021
f261c10
clang-format run.
jteuber Feb 3, 2021
d6698eb
Add test for subscript operators.
jteuber Feb 4, 2021
8129b3e
Forgot the clang-format run again ...
jteuber Feb 4, 2021
e1b5022
Simplify subscript test
jteuber Feb 5, 2021
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9 changes: 9 additions & 0 deletions include/peg_parser/interpreter.h
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
#pragma once

#include <iterator>
#include <optional>
#include <type_traits>

#include "parser.h"
Expand Down Expand Up @@ -58,6 +59,14 @@ namespace peg_parser {
Expression operator[](size_t idx) const {
return interpreter.interpret(syntaxTree->inner[idx]);
}
std::optional<Expression> operator[](std::string_view name) const {
auto it = std::find_if(syntaxTree->inner.begin(), syntaxTree->inner.end(),
[name](auto st) { return st->rule->name == name; });
if (it != syntaxTree->inner.end()) {
return interpreter.interpret(*it);
}
return {};
}
iterator begin() const { return iterator(*this, 0); }
iterator end() const { return iterator(*this, size()); }

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22 changes: 22 additions & 0 deletions test/source/parser.cpp
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Expand Up @@ -284,3 +284,25 @@ TEST_CASE("Documentation Example") {
REQUIRE(g.run("1 - 2*3/2 + 4") == Approx(2));
REQUIRE(g.run("1 + 2 * (3+4)/ 2 - 3") == Approx(5));
}

TEST_CASE("Subscript Operators") {
ParserGenerator<std::string> program;
program.setSeparator(program["Whitespace"] << "[\t ]");

program["Word"] << "[a-z]+";
program["Yell"] << "[A-Z]+";
program["Number"] << "[0-9]+";
program["IntSubscript"] << "Word Yell? Number" >> [](auto e) { return e[1].string(); };
program["StringSubscriptOptional"] << "Number Yell? Word" >> [](auto e) {
if (auto expr = e["Yell"]) return expr->string();
return std::string();
};
program["Start"] << "IntSubscript | StringSubscriptOptional";

program.setStart(program["Start"]);

REQUIRE(program.run("ab 0") == "0");
REQUIRE(program.run("ab CD 1") == "CD");
REQUIRE(program.run("2 ef") == "");
REQUIRE(program.run("2 GH ij") == "GH");
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@TheLartians TheLartians Feb 5, 2021 •
edited
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Hey, thanks for adding the test case! I do find it to be a hard to follow, as it's doing a lot of things at once. What do you think about simplifying it to a single rule that checks the new [string] operator?

For example, something like

  ParserGenerator<bool> program;
  program["Word"] << "[a-z]+";
  program["Yell"] << "[A-Z]+";
  program["Start"] << "Word | Yell" >> [](auto e){ return bool(e["Yell"]);  }
  REQUIRE(!program.run("hello"));
  REQUIRE(program.run("HELLO"));

should be enough.

}