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Added 'ignore' operator.
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yhirose
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21
README.md
21
README.md
@ -7,8 +7,9 @@ C++11 header-only [PEG](http://en.wikipedia.org/wiki/Parsing_expression_grammar)
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The PEG syntax is well described on page 2 in the [document](http://pdos.csail.mit.edu/papers/parsing:popl04.pdf). *cpp-peglib* also supports the following additional syntax for now:
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* `<` ... `>` (Anchor operators)
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* `$<` ... `>` (Capture operators)
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* `<` ... `>` (Anchor operator)
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* `$<` ... `>` (Capture operator)
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* `~` (Ignore operator)
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How to use
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----------
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@ -108,6 +109,22 @@ pg["TOKEN"] = [](const char* s, size_t l, const vector<any>& v) {
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auto ret = pg.parse(" token1, token2 ");
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```
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We can ignore unnecessary semantic values from the list by using `~` operator.
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```c++
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peglib::peg parser(
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" ROOT <- _ ITEM (',' _ ITEM _)* "
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" ITEM <- ([a-z])+ "
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" ~_ <- [ \t]* "
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);
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parser["ROOT"] = [&](const vector<any>& v) {
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assert(v.size() == 2); // should be 2 instead of 5.
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};
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auto ret = parser.parse(" item1, item2 ");
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```
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Simple interface
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----------------
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49
peglib.h
49
peglib.h
@ -153,12 +153,12 @@ private:
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*/
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struct SemanticValues
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{
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std::vector<any> values;
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//std::vector<std::string> names;
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const char* s;
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size_t l;
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std::vector<any> values;
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//std::vector<std::string> names;
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const char* s;
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size_t l;
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SemanticValues() : s(nullptr), l(0) {}
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SemanticValues() : s(nullptr), l(0) {}
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};
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/*
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@ -724,11 +724,13 @@ class Definition
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public:
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Definition()
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: actions(1)
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, ignore(false)
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, holder_(std::make_shared<Holder>(this)) {}
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Definition(const Definition& rhs)
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: name(rhs.name)
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, actions(1)
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, ignore(false)
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, holder_(rhs.holder_)
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{
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holder_->outer_ = this;
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@ -737,6 +739,7 @@ public:
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Definition(Definition&& rhs)
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: name(std::move(rhs.name))
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, actions(1)
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, ignore(rhs.ignore)
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, holder_(std::move(rhs.holder_))
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{
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holder_->outer_ = this;
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@ -744,6 +747,7 @@ public:
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Definition(const std::shared_ptr<Ope>& ope)
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: actions(1)
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, ignore(false)
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, holder_(std::make_shared<Holder>(this))
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{
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holder_->ope_ = ope;
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@ -803,8 +807,14 @@ public:
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return *this;
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}
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Definition& operator~() {
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ignore = true;
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return *this;
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}
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std::string name;
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std::vector<Action> actions;
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bool ignore;
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private:
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friend class DefinitionReference;
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@ -823,7 +833,7 @@ private:
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const auto& rule = *ope_;
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SemanticValues chldsv;
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auto r = rule.parse(s, l, chldsv, c);
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if (r.ret) {
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if (r.ret && !outer_->ignore) {
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assert(!outer_->actions.empty());
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auto id = r.choice + 1;
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@ -1011,7 +1021,7 @@ private:
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void make_grammar() {
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// Setup PEG syntax parser
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g["Grammar"] <= seq(g["Spacing"], oom(g["Definition"]), g["EndOfFile"]);
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g["Definition"] <= seq(g["Identifier"], g["LEFTARROW"], g["Expression"]);
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g["Definition"] <= seq(opt(g["IGNORE"]), g["Identifier"], g["LEFTARROW"], g["Expression"]);
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g["Expression"] <= seq(g["Sequence"], zom(seq(g["SLASH"], g["Sequence"])));
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g["Sequence"] <= zom(g["Prefix"]);
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@ -1031,7 +1041,7 @@ private:
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g["Literal"] <= cho(seq(cls("'"), anc(zom(seq(npd(cls("'")), g["Char"]))), cls("'"), g["Spacing"]),
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seq(cls("\""), anc(zom(seq(npd(cls("\"")), g["Char"]))), cls("\""), g["Spacing"]));
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g["Class"] <= seq(chr('['), anc(zom(seq(npd(chr(']')), g["Range"]))), chr(']'), g["Spacing"]);
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g["Class"] <= seq(chr('['), anc(zom(seq(npd(chr(']')), g["Range"]))), chr(']'), g["Spacing"]);
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g["Range"] <= cho(seq(g["Char"], chr('-'), g["Char"]), g["Char"]);
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g["Char"] <= cho(seq(chr('\\'), cls("nrt'\"[]\\")),
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@ -1040,7 +1050,7 @@ private:
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seq(npd(chr('\\')), dot()));
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g["LEFTARROW"] <= seq(lit("<-"), g["Spacing"]);
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g["SLASH"] <= seq(chr('/'), g["Spacing"]);
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~g["SLASH"] <= seq(chr('/'), g["Spacing"]);
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g["AND"] <= seq(chr('&'), g["Spacing"]);
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g["NOT"] <= seq(chr('!'), g["Spacing"]);
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g["QUESTION"] <= seq(chr('?'), g["Spacing"]);
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@ -1062,6 +1072,10 @@ private:
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g["BeginCap"] <= seq(lit("$<"), g["Spacing"]);
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g["EndCap"] <= seq(lit(">"), g["Spacing"]);
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g["IGNORE"] <= chr('~');
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g["Action"] <= seq(chr('{'), anc(zom(npd(chr('}')))), chr('}'), g["Spacing"]);
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// Set definition names
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for (auto& x: g) {
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x.second.name = x.first;
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@ -1072,9 +1086,16 @@ private:
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g["Definition"] = [&](const std::vector<any>& v, any& c) {
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Context& cxt = *c.get<Context*>();
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const auto& name = v[0].get<std::string>();
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(*cxt.grammar)[name] <= v[2].get<std::shared_ptr<Ope>>();
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(*cxt.grammar)[name].name = name;
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auto ignore = (v.size() == 4);
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auto baseId = ignore ? 1 : 0;
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const auto& name = v[baseId].get<std::string>();
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auto ope = v[baseId + 2].get<std::shared_ptr<Ope>>();
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auto& def = (*cxt.grammar)[name];
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def <= ope;
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def.name = name;
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def.ignore = ignore;
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if (cxt.start.empty()) {
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cxt.start = name;
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@ -1087,9 +1108,7 @@ private:
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} else {
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std::vector<std::shared_ptr<Ope>> opes;
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for (auto i = 0u; i < v.size(); i++) {
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if (!(i % 2)) {
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opes.push_back(v[i].get<std::shared_ptr<Ope>>());
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}
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opes.push_back(v[i].get<std::shared_ptr<Ope>>());
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}
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const std::shared_ptr<Ope> ope = std::make_shared<PrioritizedChoice>(opes);
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return ope;
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23
test/test.cc
23
test/test.cc
@ -76,7 +76,7 @@ TEST_CASE("String capture test2", "[general]")
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TEST_CASE("String capture test3", "[general]")
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{
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auto syntax =
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auto syntax =
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" ROOT <- _ TOKEN* "
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" TOKEN <- '[' < (!']' .)+ > ']' _ "
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" _ <- [ \t\r\n]* "
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@ -86,8 +86,8 @@ TEST_CASE("String capture test3", "[general]")
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std::vector<std::string> tags;
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pg["TOKEN"] = [&](const char* s, size_t l, const vector<any>& v) {
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tags.push_back(std::string(s, l));
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pg["TOKEN"] = [&](const char* s, size_t l) {
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tags.push_back(std::string(s, l));
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};
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auto ret = pg.parse(" [tag1] [tag:2] [tag-3] ");
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@ -147,6 +147,23 @@ TEST_CASE("Lambda action test", "[general]")
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REQUIRE(ss == "hello");
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}
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TEST_CASE("Skip token test", "[general]")
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{
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peglib::peg parser(
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" ROOT <- _ ITEM (',' _ ITEM _)* "
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" ITEM <- ([a-z])+ "
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" ~_ <- [ \t]* "
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);
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parser["ROOT"] = [&](const vector<any>& v) {
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REQUIRE(v.size() == 2);
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};
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auto ret = parser.parse(" item1, item2 ");
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REQUIRE(ret == true);
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}
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TEST_CASE("Backtracking test", "[general]")
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{
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peg parser(
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