68 lines
1.9 KiB
C#
68 lines
1.9 KiB
C#
namespace DevDisciples.Parsing;
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public abstract partial class Lexer<TToken> where TToken : Enum
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{
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protected List<Rule> Rules { get; init; } = default!;
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protected abstract TToken EndOfSource { get; }
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public List<Token> Lex(string file, string source)
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{
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var ctx = new Context(file, new Source(file, source), new List<Token>());
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while (!ctx.Source.Ended())
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{
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var matched = false;
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for (var i = 0; i < Rules.Count; i++)
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{
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if (Rules[i](ctx))
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{
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matched = true;
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break;
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}
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}
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if (!matched)
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{
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Report.Halt(ctx.Source, $"Unexpected character '{ctx.Source.Current}'.");
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}
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}
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ctx.AddToken(EndOfSource, "<EOF>", ctx.Source.Line, ctx.Source.Column);
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return ctx.Tokens;
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}
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protected static bool Match(Context ctx, TToken type, char @char)
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{
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if (!ctx.Source.Match(@char)) return false;
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var line = ctx.Source.Line;
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var column = ctx.Source.Column;
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var lexeme = ctx.Source.Extract();
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ctx.Source.Column += 1;
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ctx.AddToken(type, lexeme, line, column);
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return true;
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}
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/*
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* Do not use this method for keywords!
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* This will treat an identifier named 'ifelse' as separated 'if' and 'else' tokens.
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*/
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protected static bool Match(Context ctx, TToken token, string sequence)
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{
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if (!ctx.Source.Match(sequence)) return false;
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var line = ctx.Source.Line;
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var column = ctx.Source.Column;
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var lexeme = ctx.Source.Extract();
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ctx.Source.Column += sequence.Length;
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ctx.Tokens.Add(new Token(ctx.File, token, lexeme, line, column));
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return true;
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}
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} |