459 lines
15 KiB
C#
459 lines
15 KiB
C#
namespace Unosquare.Swan.Abstractions
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{
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using System;
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using System.Collections.Generic;
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using System.Linq;
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/// <summary>
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/// Represents a generic tokenizer.
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/// </summary>
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public abstract class Tokenizer
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{
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private const char PeriodChar = '.';
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private const char CommaChar = ',';
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private const char StringQuotedChar = '"';
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private const char OpenFuncChar = '(';
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private const char CloseFuncChar = ')';
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private const char NegativeChar = '-';
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private const string OpenFuncStr = "(";
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private readonly List<Operator> _operators = new List<Operator>();
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/// <summary>
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/// Initializes a new instance of the <see cref="Tokenizer"/> class.
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/// This constructor will use the following default operators:
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///
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/// <list type="table">
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/// <listheader>
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/// <term>Operator</term>
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/// <description>Precedence</description>
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/// </listheader>
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/// <item>
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/// <term>=</term>
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/// <description>1</description>
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/// </item>
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/// <item>
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/// <term>!=</term>
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/// <description>1</description>
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/// </item>
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/// <item>
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/// <term>></term>
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/// <description>2</description>
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/// </item>
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/// <item>
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/// <term><</term>
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/// <description>2</description>
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/// </item>
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/// <item>
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/// <term>>=</term>
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/// <description>2</description>
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/// </item>
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/// <item>
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/// <term><=</term>
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/// <description>2</description>
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/// </item>
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/// <item>
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/// <term>+</term>
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/// <description>3</description>
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/// </item>
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/// <item>
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/// <term>&</term>
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/// <description>3</description>
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/// </item>
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/// <item>
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/// <term>-</term>
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/// <description>3</description>
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/// </item>
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/// <item>
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/// <term>*</term>
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/// <description>4</description>
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/// </item>
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/// <item>
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/// <term>(backslash)</term>
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/// <description>4</description>
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/// </item>
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/// <item>
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/// <term>/</term>
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/// <description>4</description>
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/// </item>
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/// <item>
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/// <term>^</term>
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/// <description>4</description>
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/// </item>
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/// </list>
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/// </summary>
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/// <param name="input">The input.</param>
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protected Tokenizer(string input)
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{
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_operators.AddRange(GetDefaultOperators());
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Tokenize(input);
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="Tokenizer" /> class.
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/// </summary>
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/// <param name="input">The input.</param>
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/// <param name="operators">The operators to use.</param>
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protected Tokenizer(string input, IEnumerable<Operator> operators)
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{
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_operators.AddRange(operators);
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Tokenize(input);
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}
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/// <summary>
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/// Gets the tokens.
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/// </summary>
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/// <value>
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/// The tokens.
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/// </value>
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public List<Token> Tokens { get; } = new List<Token>();
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/// <summary>
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/// Validates the input and return the start index for tokenizer.
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/// </summary>
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/// <param name="input">The input.</param>
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/// <param name="startIndex">The start index.</param>
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/// <returns><c>true</c> if the input is valid, otherwise <c>false</c>.</returns>
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public abstract bool ValidateInput(string input, out int startIndex);
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/// <summary>
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/// Resolves the type of the function or member.
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/// </summary>
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/// <param name="input">The input.</param>
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/// <returns>The token type.</returns>
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public abstract TokenType ResolveFunctionOrMemberType(string input);
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/// <summary>
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/// Evaluates the function or member.
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/// </summary>
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/// <param name="input">The input.</param>
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/// <param name="position">The position.</param>
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/// <returns><c>true</c> if the input is a valid function or variable, otherwise <c>false</c>.</returns>
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public virtual bool EvaluateFunctionOrMember(string input, int position) => false;
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/// <summary>
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/// Gets the default operators.
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/// </summary>
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/// <returns>An array with the operators to use for the tokenizer.</returns>
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public virtual Operator[] GetDefaultOperators() => new[]
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{
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new Operator {Name = "=", Precedence = 1},
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new Operator {Name = "!=", Precedence = 1},
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new Operator {Name = ">", Precedence = 2},
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new Operator {Name = "<", Precedence = 2},
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new Operator {Name = ">=", Precedence = 2},
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new Operator {Name = "<=", Precedence = 2},
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new Operator {Name = "+", Precedence = 3},
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new Operator {Name = "&", Precedence = 3},
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new Operator {Name = "-", Precedence = 3},
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new Operator {Name = "*", Precedence = 4},
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new Operator {Name = "/", Precedence = 4},
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new Operator {Name = "\\", Precedence = 4},
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new Operator {Name = "^", Precedence = 4},
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};
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/// <summary>
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/// Shunting the yard.
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/// </summary>
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/// <param name="includeFunctionStopper">if set to <c>true</c> [include function stopper] (Token type <c>Wall</c>).</param>
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/// <returns>
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/// Enumerable of the token in in.
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/// </returns>
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/// <exception cref="InvalidOperationException">
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/// Wrong token
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/// or
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/// Mismatched parenthesis.
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/// </exception>
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public virtual IEnumerable<Token> ShuntingYard(bool includeFunctionStopper = true)
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{
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var stack = new Stack<Token>();
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foreach (var tok in Tokens)
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{
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switch (tok.Type)
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{
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case TokenType.Number:
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case TokenType.Variable:
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case TokenType.String:
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yield return tok;
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break;
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case TokenType.Function:
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stack.Push(tok);
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break;
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case TokenType.Operator:
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while (stack.Any() && stack.Peek().Type == TokenType.Operator &&
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CompareOperators(tok.Value, stack.Peek().Value))
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yield return stack.Pop();
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stack.Push(tok);
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break;
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case TokenType.Comma:
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while (stack.Any() && (stack.Peek().Type != TokenType.Comma &&
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stack.Peek().Type != TokenType.Parenthesis))
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yield return stack.Pop();
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break;
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case TokenType.Parenthesis:
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if (tok.Value == OpenFuncStr)
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{
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if (stack.Any() && stack.Peek().Type == TokenType.Function)
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{
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if (includeFunctionStopper)
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yield return new Token(TokenType.Wall, tok.Value);
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}
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stack.Push(tok);
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}
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else
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{
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while (stack.Peek().Value != OpenFuncStr)
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yield return stack.Pop();
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stack.Pop();
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if (stack.Any() && stack.Peek().Type == TokenType.Function)
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{
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yield return stack.Pop();
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}
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}
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break;
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default:
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throw new InvalidOperationException("Wrong token");
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}
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}
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while (stack.Any())
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{
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var tok = stack.Pop();
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if (tok.Type == TokenType.Parenthesis)
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throw new InvalidOperationException("Mismatched parenthesis");
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yield return tok;
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}
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}
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private static bool CompareOperators(Operator op1, Operator op2) => op1.RightAssociative
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? op1.Precedence < op2.Precedence
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: op1.Precedence <= op2.Precedence;
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private void Tokenize(string input)
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{
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if (!ValidateInput(input, out var startIndex))
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{
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return;
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}
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for (var i = startIndex; i < input.Length; i++)
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{
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if (char.IsWhiteSpace(input, i)) continue;
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if (input[i] == CommaChar)
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{
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Tokens.Add(new Token(TokenType.Comma, new string(new[] { input[i] })));
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continue;
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}
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if (input[i] == StringQuotedChar)
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{
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i = ExtractString(input, i);
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continue;
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}
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if (char.IsLetter(input, i) || EvaluateFunctionOrMember(input, i))
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{
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i = ExtractFunctionOrMember(input, i);
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continue;
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}
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if (char.IsNumber(input, i) || (
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input[i] == NegativeChar &&
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((Tokens.Any() && Tokens.Last().Type != TokenType.Number) || !Tokens.Any())))
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{
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i = ExtractNumber(input, i);
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continue;
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}
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if (input[i] == OpenFuncChar ||
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input[i] == CloseFuncChar)
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{
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Tokens.Add(new Token(TokenType.Parenthesis, new string(new[] { input[i] })));
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continue;
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}
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i = ExtractOperator(input, i);
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}
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}
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private int ExtractData(
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string input,
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int i,
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Func<string, TokenType> tokenTypeEvaluation,
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Func<char, bool> evaluation,
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int right = 0,
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int left = -1)
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{
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var charCount = 0;
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for (var j = i + right; j < input.Length; j++)
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{
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if (evaluation(input[j]))
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break;
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charCount++;
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}
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// Extract and set the value
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var value = input.SliceLength(i + right, charCount);
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Tokens.Add(new Token(tokenTypeEvaluation(value), value));
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i += charCount + left;
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return i;
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}
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private int ExtractOperator(string input, int i) =>
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ExtractData(input, i, x => TokenType.Operator, x => x == OpenFuncChar ||
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x == CommaChar ||
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x == PeriodChar ||
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x == StringQuotedChar ||
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char.IsWhiteSpace(x) ||
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char.IsNumber(x));
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private int ExtractFunctionOrMember(string input, int i) =>
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ExtractData(input, i, ResolveFunctionOrMemberType, x => x == OpenFuncChar ||
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x == CloseFuncChar ||
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x == CommaChar ||
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char.IsWhiteSpace(x));
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private int ExtractNumber(string input, int i) =>
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ExtractData(input, i, x => TokenType.Number,
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x => !char.IsNumber(x) && x != PeriodChar && x != NegativeChar);
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private int ExtractString(string input, int i)
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{
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var length = ExtractData(input, i, x => TokenType.String, x => x == StringQuotedChar, 1, 1);
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// open string, report issue
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if (length == input.Length && input[length - 1] != StringQuotedChar)
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throw new FormatException($"Parser error (Position {i}): Expected '\"' but got '{input[length - 1]}'.");
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return length;
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}
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private bool CompareOperators(string op1, string op2)
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=> CompareOperators(GetOperatorOrDefault(op1), GetOperatorOrDefault(op2));
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private Operator GetOperatorOrDefault(string op)
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=> _operators.FirstOrDefault(x => x.Name == op) ?? new Operator { Name = op, Precedence = 0 };
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}
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/// <summary>
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/// Represents an operator with precedence.
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/// </summary>
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public class Operator
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{
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/// <summary>
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/// Gets or sets the name.
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/// </summary>
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/// <value>
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/// The name.
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/// </value>
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public string Name { get; set; }
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/// <summary>
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/// Gets or sets the precedence.
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/// </summary>
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/// <value>
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/// The precedence.
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/// </value>
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public int Precedence { get; set; }
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/// <summary>
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/// Gets or sets a value indicating whether [right associative].
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/// </summary>
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/// <value>
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/// <c>true</c> if [right associative]; otherwise, <c>false</c>.
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/// </value>
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public bool RightAssociative { get; set; }
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}
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/// <summary>
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/// Represents a Token structure.
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/// </summary>
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public struct Token
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{
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/// <summary>
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/// Initializes a new instance of the <see cref="Token"/> struct.
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/// </summary>
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/// <param name="type">The type.</param>
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/// <param name="value">The value.</param>
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public Token(TokenType type, string value)
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{
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Type = type;
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Value = type == TokenType.Function || type == TokenType.Operator ? value.ToLowerInvariant() : value;
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}
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/// <summary>
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/// Gets or sets the type.
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/// </summary>
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/// <value>
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/// The type.
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/// </value>
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public TokenType Type { get; set; }
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/// <summary>
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/// Gets the value.
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/// </summary>
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/// <value>
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/// The value.
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/// </value>
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public string Value { get; }
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}
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/// <summary>
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/// Enums the token types.
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/// </summary>
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public enum TokenType
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{
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/// <summary>
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/// The number
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/// </summary>
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Number,
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/// <summary>
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/// The string
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/// </summary>
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String,
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/// <summary>
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/// The variable
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/// </summary>
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Variable,
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/// <summary>
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/// The function
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/// </summary>
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Function,
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/// <summary>
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/// The parenthesis
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/// </summary>
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Parenthesis,
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/// <summary>
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/// The operator
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/// </summary>
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Operator,
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/// <summary>
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/// The comma
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/// </summary>
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Comma,
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/// <summary>
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/// The wall, used to specified the end of argument list of the following function
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/// </summary>
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Wall,
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}
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} |