/// <summary>
///This will take in one line, the two matrices to enter the values in, the variable characters and if it is the first line or not.
///it will parse it to get the one or two coefficients and the answer from the input
/// </summary>
/// <param name="input">This is the string that will be parsed to get</param>
/// <param name="coefficients">this matrix holds the values of the coefficients for the variables from both equations</param>
/// <param name="answers">this matrix holds the answers from both equations</param>
/// <param name="var1">this is the value of the first variable (it is ' ' if it has not been assigned)</param>
/// <param name="var2">this is the value of the second variable (it is ' ' if it has not been assigned)</param>
/// <param name="firstLine">this will determine if it is the first line to be parsed</param>
/// <returns>This only passes values by reference, there is no return</returns>
public static void parseEquation(string input, Matrix coefficients, Matrix answers, ref char var1, ref char var2, bool firstLine)
{
int index = 0;
double temp;
int line = (firstLine)? LINE1: LINE2; //this will determine which lines values are being parsed
char nextVar; //this will hold the other variable that has not been assigned on
int nextVarIndex;
temp = Parsing.parseCoefficient(input, ref index); //parse the string for the first coefficient
if (firstLine) //this means that var1 has not been assigned yet
{
#region Save first variable and coefficient
coefficients.SetCell(line, VAR1, temp); //assign the value for the first coefficient
var1 = Char.ToLower(input[index]); //get the variable at the index after the coefficient
#endregion
index++; //increment to check next character
#region Check second part of the equation for variable or answer
switch (input[index]) //is it the end of the equation or is there a second variable
{
#region go to answer
case '=': //no second coefficient, go straight to answer
coefficients.SetCell(line, VAR2, 0); //assign 0 to second variable
index++; //start the index after the equals sign for parsing
answers.SetCell(line, 0, Parsing.parseDouble(input, ref index)); //get the answer to the equation
break;
#endregion
#region save second coefficient and variable and answer
case '+': //there is a second variable
case '-':
#region save second coefficient and variable
temp = Parsing.parseCoefficient(input, ref index); //get second variable coefficient
if (input[index] == var1) //if the second variable is the same as the first throw an exception
{
throw new ParseException("Invalid characters detected, double use of the same variable!");
}
coefficients.SetCell(line, VAR2, temp);
var2 = Char.ToLower(input[index]); //store the second variable
index++; //increment to check next character
if (input[index] != '=')
{
throw new ParseException("Invalid characters detected at index " + index + ". Must be \"=\"");
}
else
{
index++; //increment to check next character
}
#endregion
#region save answer
answers.SetCell(line, 0, Parsing.parseDouble(input, ref index)); //get answer from the end of the input
#endregion
break;
default:
throw new ParseException("Invalid characters detected at index " + index);
#endregion
}
#endregion
}
else //this is the second line
{
#region check variable to assign coefficient
if (input[index] == var1) //assign to the coefficient corresponsing to the variable
{
coefficients.SetCell(line, VAR1, temp); //assign the value for the first coefficient
nextVar = Char.ToLower(var2);
nextVarIndex = VAR2;
}
else if (input[index] == var2)
{
coefficients.SetCell(line, VAR2, temp); //assign the value for the second coefficient
nextVar = Char.ToLower(var1);
nextVarIndex = VAR1;
}
else if (var2 == UNASSIGNED)
{
var2 = input[index]; //assign the previously empty var2
coefficients.SetCell(line, VAR2, temp);
nextVar = Char.ToLower(var1);
nextVarIndex = VAR1;
}
else
{
throw new ParseException("Invalid variable detected at line: " + line + ", index: " + index);
}
#endregion
index++; //increment to check next character
#region Check second part of the equation
switch (input[index]) //is it the end of the equation or is there a second variable
{
#region go to answer
case '=': //no second coefficient, go straight to answer
coefficients.SetCell(line, nextVarIndex, 0); //assign 0 to second variable
index++; //start the index after the equals sign for parsing
answers.SetCell(line, 0, Parsing.parseDouble(input, ref index)); //get the answer to the equation
break;
#endregion
#region save second coefficient and variable and answer
case '+': //there is a second variable
case '-':
#region save second coefficient and variable
coefficients.SetCell(line, nextVarIndex, Parsing.parseCoefficient(input, ref index)); //get second variable coefficient
if (input[index] != nextVar) //if the second variable is the same as the first throw an exception
{
throw new ParseException("Invalid characters detected, invalid second variable");
}
index++; //increment to check next character
if (input[index] != '=') //it needs to be an equal sign or is does not work
{
throw new ParseException("Invalid characters detected at index " + index + ". Must be \"=\"");
}
else
{
index++; //increment to check next character
}
#endregion
#region save answer
answers.SetCell(line, 0, Parsing.parseDouble(input, ref index));
#endregion
break;
default:
throw new ParseException("Invalid characters detected at index " + index);
#endregion
}
#endregion
}
}
