91 lines
2.0 KiB
C#
91 lines
2.0 KiB
C#
namespace Canon.Core.GrammarParser;
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/// <summary>
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/// LR语法中的一个表达式，例如 'program_struct -> ~program_head ; program_body'
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/// 其中'~'标识当前移进到达的位置
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/// </summary>
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public class Expression : IEquatable<Expression>
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{
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/// <summary>
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/// 表达式的左部
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/// </summary>
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public required NonTerminator Left { get; init; }
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/// <summary>
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/// 表达式的向前看字符串
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/// </summary>
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public required Terminator LookAhead { get; init; }
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/// <summary>
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/// 表达式的右部
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/// </summary>
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public required List<TerminatorBase> Right { get; init; }
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/// <summary>
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/// 当前移进的位置
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/// </summary>
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public int Pos { get; set; }
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public bool Equals(Expression? other)
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{
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if (other is null)
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{
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return false;
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}
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if (Right.Count != other.Right.Count)
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{
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return false;
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}
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for (int i = 0; i < Right.Count; i++)
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{
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if (Right[i].IsTerminated != other.Right[i].IsTerminated)
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{
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return false;
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}
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if (!Right[i].Equals(other.Right[i]))
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{
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return false;
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}
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}
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return Left == other.Left
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&& LookAhead == other.LookAhead;
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}
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public override bool Equals(object? obj)
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{
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if (obj is not Expression other)
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{
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return false;
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}
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return Equals(other);
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}
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public override int GetHashCode()
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{
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int hash = Left.GetHashCode();
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hash ^= LookAhead.GetHashCode();
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foreach (TerminatorBase terminator in Right)
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{
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hash ^= terminator.GetHashCode();
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}
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return hash;
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}
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public static bool operator ==(Expression a, Expression b)
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{
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return a.Equals(b);
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}
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public static bool operator !=(Expression a, Expression b)
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{
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return !a.Equals(b);
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}
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}
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