339 lines
10 KiB
C++
339 lines
10 KiB
C++
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#include <iostream>
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#include <vector>
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#include <string>
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#include <unordered_map>
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#include <unordered_set>
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#include <list>
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#define EMPTY L'ε'
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#define END L'$'
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struct Grammar
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{
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std::unordered_map<wchar_t, std::vector<std::wstring>> Generators;
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std::unordered_set<wchar_t> Nonterminators;
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wchar_t Begin;
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std::unordered_map<wchar_t, std::unordered_set<wchar_t>> FirstSet;
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std::unordered_map<wchar_t, std::unordered_set<wchar_t>> FollowSet;
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std::unordered_map<wchar_t, std::unordered_map<wchar_t, std::wstring>> AnalysisTable;
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Grammar(const std::unordered_map<wchar_t, std::vector<std::wstring>>&generators, const wchar_t begin)
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{
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Generators = generators;
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Begin = begin;
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for (const auto&[key, value]: generators)
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{
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Nonterminators.emplace(key);
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FirstSet.emplace(key, std::unordered_set<wchar_t>());
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FollowSet.emplace(key, std::unordered_set<wchar_t>());
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AnalysisTable.emplace(key, std::unordered_map<wchar_t, std::wstring>());
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}
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// 求非终结符的FIRST集合
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bool changed = true;
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while (changed)
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{
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changed = false;
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for (const auto&[key, value]: generators)
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{
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for (const auto&expression: value)
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{
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if (Nonterminators.count(expression.front()) != 0)
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{
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// 合并其他非终结符的FIRST集合
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for (const auto&c: FirstSet[expression.front()])
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{
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if (c != EMPTY and FirstSet[key].count(c) == 0)
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{
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FirstSet[key].emplace(c);
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changed = true;
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}
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}
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}
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else
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{
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if (FirstSet[key].count(expression.front()) == 0)
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{
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FirstSet[key].emplace(expression.front());
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changed = true;
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}
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}
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}
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}
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}
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// 求非终结符的FOLLOW集合
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changed = true;
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FollowSet[begin].emplace(END);
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while (changed)
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{
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changed = false;
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for (const auto&[key, value]: generators)
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{
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for (const auto&expression: value)
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{
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for (auto i = expression.begin(); i != expression.end(); ++i)
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{
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if (Nonterminators.count(*i) != 0)
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{
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// 发现非终结符
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auto next = i;
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++next;
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if (next == expression.end())
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{
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// 非终结符在表达式末尾
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for (const auto&c: FollowSet[key])
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{
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if (FollowSet[*i].count(c) == 0)
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{
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FollowSet[*i].emplace(c);
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changed = true;
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}
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}
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continue;
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}
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std::wstring newExpression;
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while (next != expression.end())
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{
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newExpression += *next;
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++next;
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}
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const auto&firstSet = GetFirstSet(newExpression);
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for (const auto&c: firstSet)
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{
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if (c == EMPTY)
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{
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for (const auto&j: FollowSet[key])
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{
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if (FollowSet[*i].count(j) == 0)
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{
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FollowSet[*i].emplace(j);
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changed = true;
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}
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}
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}
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else
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{
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if (FollowSet[*i].count(c) == 0)
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{
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FollowSet[*i].emplace(c);
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changed = true;
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}
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}
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}
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}
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}
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}
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}
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}
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// 生成预测分析表
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for (const auto&[key, array]: Generators)
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{
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for (const auto&expression: array)
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{
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const auto&firstSet = GetFirstSet(expression);
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for (const auto&c: firstSet)
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{
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if (c == EMPTY)
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{
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for (const auto&i: FollowSet.at(key))
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{
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if (!AnalysisTable[key].emplace(i, expression).second)
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{
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std::cout << "Error, not LL(1) grammar!" << std::endl;
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}
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}
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}
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else
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{
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if (!AnalysisTable[key].emplace(c, expression).second)
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{
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std::cout << "Error, not LL(1) grammar!" << std::endl;
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}
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}
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}
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}
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}
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}
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std::unordered_set<wchar_t> GetFirstSet(const std::wstring&expression) const
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{
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std::unordered_set<wchar_t> set;
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if (Nonterminators.count(expression.front()) != 0)
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{
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// 起手是非终结符
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for (const auto&c: FirstSet.at(expression.front()))
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{
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// 只有所有的符号都能推出空串 才添加
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if (c == EMPTY)
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{
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bool flag = true;
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for (const auto&i: expression)
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{
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if (Nonterminators.count(i) != 0)
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{
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flag = FirstSet.at(i).count(EMPTY) != 0;
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}
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else
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{
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flag = i == EMPTY;
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}
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if (!flag)
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{
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break;
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}
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}
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if (flag)
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{
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set.emplace(EMPTY);
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}
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}
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else
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{
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set.emplace(c);
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}
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}
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}
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else
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{
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set.emplace(expression.front());
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}
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return set;
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}
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void Analyse(const std::wstring& input, const std::unordered_map<std::wstring, int>& numbers)
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{
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std::list<wchar_t> states;
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auto i = input.begin();
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states.emplace_back(END);
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states.emplace_back(Begin);
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do
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{
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for (const auto c : states)
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{
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std::wcout << c;
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}
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std::wcout << L'\t';
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for (auto j = i; j != input.end(); ++j)
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{
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std::wcout << *j;
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}
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std::wcout << L'\t';
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if (auto top = states.back(); Nonterminators.count(top) != 0)
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{
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// 栈顶是非终结符
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if (AnalysisTable[top].count(*i) == 0)
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{
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std::wcout << L"error" << std::endl;
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break;
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}
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states.pop_back();
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if (AnalysisTable[top][*i].front() != EMPTY)
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{
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// 如果是空串还是不要加了
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for (auto j = AnalysisTable[top][*i].rbegin(); j != AnalysisTable[top][*i].rend(); ++j)
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{
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states.emplace_back(*j);
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}
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}
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auto expression = top + AnalysisTable[top][*i];
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std::wcout << numbers.at(expression);
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}
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else
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{
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if (top == *i)
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{
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if (top == END)
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{
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std::wcout << L"accept";
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}
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else
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{
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std::wcout << L"match";
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}
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states.pop_back();
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++i;
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}
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else
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{
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std::wcout << L"error" << std::endl;
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break;
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}
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}
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std::wcout << std::endl;
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}
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while (!states.empty());
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}
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};
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int main()
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{
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const std::unordered_map<wchar_t, std::vector<std::wstring>> map = {
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{'E', {L"TA"}},
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{'A', {L"+TA", L"-TA", L"ε"}},
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{'T', {L"FB"}},
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{'B', {L"ε", L"*FB", L"/FB"}},
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{'F', {L"(E)", L"n"}}
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};
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// 通过另外的表输入产生式编号
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const std::unordered_map<std::wstring, int> numbers = {
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{L"ETA", 1},
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{L"A+TA", 2},
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{L"A-TA", 3},
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{L"Aε", 4},
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{L"TFB", 5},
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{L"B*FB", 6},
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{L"B/FB", 7},
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{L"Bε", 8},
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{L"F(E)", 9},
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{L"Fn", 10}
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};
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/**
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FIRST
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E -> n (
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A -> e - +
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T -> ( n
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B -> / * e
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F -> n (
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FOLLOW
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E -> ) $
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A -> $ )
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T -> $ ) - +
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B -> + - ) $
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F -> + - ) $ / *
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*/
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Grammar grammar(map, 'E');
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std::wstring input;
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std::wcin >> input;
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input += END;
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grammar.Analyse(input, numbers);
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return 0;
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}
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