add: GrammarBuilder

This commit is contained in:
jackfiled 2024-03-10 15:37:18 +08:00
parent 58da63e41a
commit 6f8fb4c54e
5 changed files with 281 additions and 0 deletions

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@ -2,6 +2,10 @@
public enum NonTerminatorType
{
/// <summary>
/// 拓广文法
/// </summary>
StartNonTerminator,
ProgramStruct,
ProgramHead,
ProgramBody,

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@ -8,6 +8,10 @@ public enum SemanticTokenType
Delimiter,
Identifier,
Character,
/// <summary>
/// 语法分析中的栈底符号
/// </summary>
End
}
public enum DelimiterType

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@ -0,0 +1,8 @@
namespace Canon.Core.GrammarParser;
public class Grammar
{
public required NonTerminator Begin { get; init; }
public required LrState BeginState { get; init; }
}

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@ -0,0 +1,260 @@
namespace Canon.Core.GrammarParser;
public class GrammarBuilder
{
/// <summary>
/// 指定文法的生成式
/// </summary>
public Dictionary<NonTerminator, List<List<TerminatorBase>>> Generators { get; } = [];
/// <summary>
/// 文法的起始符
/// </summary>
public required NonTerminator Begin { get; init; }
/// <summary>
/// 文法中所有非终结符的First集合
/// </summary>
public Dictionary<NonTerminator, HashSet<Terminator>> FirstSet { get; } = [];
public HashSet<LrState> Automation { get; } = [];
/// <summary>
/// 构建文法中所有非终结符的First集合
/// </summary>
private void BuildFirstSet()
{
bool changed = true;
while (changed)
{
changed = false;
foreach (KeyValuePair<NonTerminator, List<List<TerminatorBase>>> pair in Generators)
{
foreach (List<TerminatorBase> expression in pair.Value)
{
// 对于空产生式直接跳过处理是正确的吗?
TerminatorBase? expressionHead = expression.FirstOrDefault();
if (expressionHead is null)
{
continue;
}
if (expressionHead.IsTerminated)
{
// 产生式的第一个字符是终结符
// 将这个终结符加入该非终结符的First集合
Terminator terminator = (Terminator)expressionHead;
if (FirstSet.TryAdd(pair.Key, [terminator]))
{
changed = true;
}
else
{
if (FirstSet[pair.Key].Add(terminator))
{
changed = true;
}
}
}
else
{
NonTerminator nonTerminator = (NonTerminator)expressionHead;
// 产生式的第一个字符是非终结符
// 将该非终结符的结果合并到该
if (FirstSet.TryGetValue(nonTerminator, out HashSet<Terminator>? value))
{
foreach (Terminator first in value)
{
if (FirstSet.TryAdd(pair.Key, [first]))
{
changed = true;
}
else
{
if (FirstSet[pair.Key].Add(first))
{
changed = true;
}
}
}
}
}
}
}
}
}
/// <summary>
/// 计算指定语句的First集合
/// 需要用到非终结符的First集合
/// </summary>
/// <param name="expression">需要计算的语句</param>
/// <returns>指定语句的First集合</returns>
private HashSet<Terminator> CalculateFirstSetOfExpression(List<TerminatorBase> expression)
{
HashSet<Terminator> result = [];
TerminatorBase? expressionHead = expression.FirstOrDefault();
if (expressionHead is null)
{
return result;
}
if (expressionHead.IsTerminated)
{
// 指定表达式开头是终结符
Terminator terminator = (Terminator)expressionHead;
result.Add(terminator);
}
else
{
// 指定表达式开头是非终结符
// 将该非终结符的FirstSet加入进来
NonTerminator nonTerminator = (NonTerminator)expressionHead;
if (FirstSet.TryGetValue(nonTerminator, out HashSet<Terminator>? firstSet))
{
result.UnionWith(firstSet);
}
}
return result;
}
/// <summary>
/// 计算指定表达式的项目集规范族闭包
/// </summary>
/// <param name="expression">指定的表达式</param>
/// <returns>指定表达式的项目集规范族闭包</returns>
private HashSet<Expression> CalculateClosure(Expression expression)
{
HashSet<Expression> closure = [expression];
bool changed = true;
while (changed)
{
changed = false;
foreach (Expression e in closure)
{
TerminatorBase next = e.Right[e.Pos];
if (next.IsTerminated)
{
continue;
}
NonTerminator nonTerminator = (NonTerminator)next;
// 将当前未移进的字符和向前看字符拼接为新的向前看表达式
List<TerminatorBase> ahead = [];
for (int i = e.Pos + 1; i < e.Right.Count; i++)
{
ahead.Add(e.Right[i]);
}
ahead.Add(e.LookAhead);
HashSet<Terminator> lookAheadSet = CalculateFirstSetOfExpression(ahead);
foreach (List<TerminatorBase> nextExpression in Generators[nonTerminator])
{
foreach (Terminator lookAhead in lookAheadSet)
{
Expression newExpression = new()
{
Left = nonTerminator, Right = nextExpression, LookAhead = lookAhead
};
if (closure.Add(newExpression))
{
changed = true;
}
}
}
}
}
return closure;
}
public Grammar Build()
{
// 开始之前构建FirstSet
BuildFirstSet();
Expression begin = new()
{
Left = Begin, Right = Generators[Begin].First(), LookAhead = Terminator.EndTerminator
};
LrState beginState = new() { Expressions = CalculateClosure(begin) };
Automation.Add(beginState);
bool added = true;
while (added)
{
added = false;
foreach (LrState state in Automation)
{
// 表示使用key进行移进可以生成的新LR(1)句型
Dictionary<TerminatorBase, List<Expression>> nextExpressions = [];
foreach (Expression e in state.Expressions)
{
Expression nextExpression = new()
{
Left = e.Left, Right = e.Right, LookAhead = e.LookAhead, Pos = e.Pos
};
if (nextExpression.Pos >= nextExpression.Right.Count)
{
// 移进符号已经到达句型的末尾
continue;
}
nextExpression.Pos += 1;
TerminatorBase next = nextExpression.Right[nextExpression.Pos];
if (!nextExpressions.TryAdd(next, [nextExpression]))
{
nextExpressions[next].Add(nextExpression);
}
}
foreach (KeyValuePair<TerminatorBase,List<Expression>> pair in nextExpressions)
{
// 针对每个构建项目集闭包
HashSet<Expression> closure = [];
foreach (Expression expression in pair.Value)
{
closure.UnionWith(CalculateClosure(expression));
}
LrState newState = new() { Expressions = closure };
if (Automation.TryGetValue(newState, out LrState? oldState))
{
// 存在这个项目集闭包
state.Transformer.Add(pair.Key, oldState);
}
else
{
// 不存在这个项目集闭包
Automation.Add(newState);
state.Transformer.Add(pair.Key, newState);
added = true;
}
}
}
}
return new Grammar { Begin = Begin, BeginState = beginState };
}
}

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@ -63,6 +63,11 @@ public class Terminator : TerminatorBase, IEquatable<Terminator>
/// </summary>
public static Terminator NumberTerminator => new(SemanticTokenType.Number);
/// <summary>
/// 栈底的终结符
/// </summary>
public static Terminator EndTerminator => new(KeywordType.End);
public override int GetHashCode()
{
int hash = _terminatorType.GetHashCode();