/// <summary>
/// Creates an <see cref="IEnumerable{Token}" /> containing infix tokens from partitioning the specified term.
/// </summary>
/// <param name="term">The term to partition into infix tokens.</param>
/// <returns><see cref="IEnumerable{Token}" /> containing the created infix tokens.</returns>
public static IEnumerable <Token> CalculateInfixTokens(string term)
{
var infixTokens = new List <Token>();
term = SWhitespace.Replace(term, string.Empty).ToLowerInvariant();
var i = 0;
while (i < term.Length)
{
var current = term[i];
if (char.IsLetter(current) || CharEx.IsMathematicOperator(current) || CharEx.IsBracket(current))
// Functions/Operators/Constants
{
if ((current == '+' || current == '-') &&
(i == 0 ||
infixTokens.Last().Type == TokenType.Bracket &&
((Token <string>)infixTokens.Last()).Value == "("))
// Must be a sign and handled differently.
{
if (current == '-')
{
var sb = new StringBuilder(term)
{
[term.IndexOf(current)] = '!'
};
term = sb.ToString();
}
else
{
term.Remove(term.IndexOf(current), 1);
}
// Remove the '+' as it is redundant and disturbs our calculations
}
infixTokens.Add(ReadStringToken(term, ref i));
}
else if (char.IsDigit(current)) // Numbers
{
infixTokens.Add(ReadNumberToken(term, ref i));
}
else
{
throw new ParserException($"Char {current} cannot be interpreted as a valid token.");
}
}
return(infixTokens);
}
/// <summary>
/// Reads a bracket, constant, operator or function token in the input string starting at the specified index.
/// </summary>
/// <param name="input">The input string.</param>
/// <param name="index">The index to start at.</param>
/// <returns>The <see cref="Token" /> that has been read.</returns>
public static Token <string> ReadStringToken(string input, ref int index)
{
TokenType newType;
var endIndex = index;
while (endIndex < input.Length &&
(char.IsLetter(input, endIndex) || CharEx.IsMathematicOperator(input[endIndex]) ||
CharEx.IsBracket(input[endIndex])))
{
endIndex++;
var currentString = input.Substring(index, endIndex - index);
if (_functionActions.ContainsKey(currentString) || _operatorActions.ContainsKey(currentString) ||
_constantActions.ContainsKey(currentString) ||
currentString.IsBracket()
) // Last two conditions to parse e.g. "* sin(5)" correctly: As soon as the current token has finished, we should stop reading.
{
break; // This indicates that it has been found in the dictionary, so that is already it.
}
}
var stringToken = input.Substring(index, endIndex - index);
if (_functionActions.ContainsKey(stringToken))
{
newType = TokenType.Function;
}
else if (_operatorActions.ContainsKey(stringToken))
{
newType = TokenType.Operator;
}
else if (stringToken.IsBracket())
{
newType = TokenType.Bracket;
}
else if (_constantActions.ContainsKey(stringToken))
{
newType = TokenType.Constant;
}
else
{
throw new ParserException(
$"Invalid token: {stringToken} is not a valid function/operator, bracket or number equivalent.");
}
index = endIndex;
return(new Token <string>(stringToken, newType));
}
/// <summary>
/// Reads a bracket, operator or function token in the input string starting at the specified index.
/// </summary>
/// <param name="input">The input string.</param>
/// <param name="index">The index to start at.</param>
/// <returns>The <see cref="Token" /> that has been read.</returns>
public static Token <string> ReadStringToken(string input, ref int index)
{
TokenType newType;
int endIndex = index;
while (endIndex < input.Length &&
(char.IsLetter(input, endIndex) || CharEx.IsMathematicOperator(input[endIndex]) ||
CharEx.IsBracket(input[endIndex])))
{
endIndex++;
string currentString = input.Substring(index, endIndex - index);
if (_functionActions.ContainsKey(currentString) || _operatorActions.ContainsKey(currentString) ||
currentString.IsBracket()) // Last two conditions to parse e.g. "* sin(5)" correctly
{
break;
}
}
string stringToken = input.Substring(index, endIndex - index);
if (_functionActions.ContainsKey(stringToken))
{
newType = TokenType.Function;
}
else if (_operatorActions.ContainsKey(stringToken))
{
newType = TokenType.Operator;
}
else if (stringToken.IsBracket())
{
newType = TokenType.Bracket;
}
else
{
throw new ParserException(
$"Invalid token: {stringToken} is not a valid function/operator, bracket or number equivalent.");
}
index = endIndex;
return(new Token <string>(stringToken, newType));
}
