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73 lines
1.5 KiB
73 lines
1.5 KiB
//
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// indent.cc
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//
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// Copyright (c) 2022 Yuji Hirose. All rights reserved.
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// MIT License
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//
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// Based on https://gist.github.com/dmajda/04002578dd41ae8190fc
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#include <cstdlib>
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#include <iostream>
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#include <peglib.h>
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using namespace peg;
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int main(void) {
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parser parser(R"(Start <- Statements {}
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Statements <- Statement*
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Statement <- Samedent (S / I)
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S <- 'S' EOS { no_ast_opt }
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I <- 'I' EOL Block / 'I' EOS { no_ast_opt }
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Block <- Statements {}
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~Samedent <- ' '* {}
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~EOS <- EOL / EOF
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~EOL <- '\n'
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~EOF <- !.
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)");
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size_t indent = 0;
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parser["Block"].enter = [&](const Context & /*c*/, const char * /*s*/,
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size_t /*n*/, std::any & /*dt*/) { indent += 2; };
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parser["Block"].leave = [&](const Context & /*c*/, const char * /*s*/,
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size_t /*n*/, size_t /*matchlen*/,
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std::any & /*value*/,
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std::any & /*dt*/) { indent -= 2; };
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parser["Samedent"].predicate =
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[&](const SemanticValues &vs, const std::any & /*dt*/, std::string &msg) {
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if (indent != vs.sv().size()) {
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msg = "different indent...";
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return false;
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}
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return true;
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};
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parser.enable_ast();
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const auto source = R"(I
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S
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I
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I
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S
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S
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S
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S
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)";
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std::shared_ptr<Ast> ast;
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if (parser.parse(source, ast)) {
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ast = parser.optimize_ast(ast);
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std::cout << ast_to_s(ast);
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return 0;
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}
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std::cout << "syntax error..." << std::endl;
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return -1;
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}
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