//This function takes in the iterator, and rewrite both sides of the sum expression in postFix
//Pre- The position is at a symbol +,-,*,/,%
//Post- It will change postFix and the iterator
void addOp(ListIterator &iter, TokenList &postFix)
{
int pos;
Token saveToken;
bool solved = false;
while(solved == false)
{
if (iter.tokenChar() == '*' || iter.tokenChar() == '/' || iter.tokenChar() == '%')
{
//This means that a product operation was encountered immediately so the prgoram can finish the expression and return without
multOp(iter, postFix);
}
else if (iter.tokenChar() == '+' || iter.tokenChar() == '-')
{
//We advance to save the next number and then again to check the next character
saveToken = iter.token();
iter.advance();
getValue(iter, postFix);
iter.advance();
if (iter.tokenChar() == '*' || iter.tokenChar() == '/' || iter.tokenChar() == '%')
{
//If a product expression is found it will calculate the entirety of that
multOp(iter, postFix);
}
postFix.push_back(saveToken);
}
else
{
solved = true;
}
}
}
// getValue
// Gets the value of the number/expression at the current position
// If the current value is an integer, return it
// If it's a parenthetical expression, evaluate, and return
// evalMultiplication is a flag used to ensure multiplication happens before addition
// If true, it will handle any multiplication that is applied to the current value
// That way, what is returned to the addition function is what we actually want to add
// Parameters:
// iter - the iterator for the list of tokens
// postExpr - the postfix expression we are converting to
// evalMultiplication (input boolean) whether to evaluate multiplication, see above
// Pre-condition: expr[pos] is an int or parenthesis
// Post-condition: expr[pos] is the end of the value
// If it was an int, it's on the int
// If it was a parenthesis, it's on the end parenthesis
// If handling multiplication, it's on the last multiplied int
// postExpr has the values handled here pushed to it
void getValue(ListIterator& iter, TokenList& postExpr, bool evalMultiplication)
{
bool negative = false;
if (!iter.currentIsInteger() && iter.tokenChar() == '-')
{
negative = true;
iter.advance();
}
if (iter.currentIsInteger())
{
postExpr.push_back(iter.integerValue());
if (negative)
{
postExpr.push_back(Token('~'));
}
while (evalMultiplication && isNextOperatorMultiplication(iter))
{
iter.advance();
handleMultiplyLevelOperation(iter, postExpr);
}
}
else
{
handleParenthesis(iter, postExpr);
if (negative)
{
postExpr.push_back(Token('~'));
}
}
}
//This function takes in the iterator, and the TokeList, and will rewrite any product expressions
//Pre- The position will be on a operation symbol that is either *, /, %
//Post- It will rewrite the infix to postFix product expression
void multOp(ListIterator &iter, TokenList &postFix)
{
Token saveToken;
//This loop will run indefinately and rewrite to postFix until the product expression ends
while (iter.tokenChar() == '*' || iter.tokenChar() == '/' || iter.tokenChar() == '%')
{
saveToken = iter.token();
iter.advance();
getValue(iter, postFix);
iter.advance();
postFix.push_back(saveToken);
}
}
// handleParenthesis
// Helper function to handle evaluating parenthesis
// Parameters:
// iter - the iterator for the list of tokens
// postExpr - the postfix expression we are converting to
// Pre-condition: iter.tokenChar() == '('
// Post-condition: iter.tokenChar() == ')'
// postExpr has everything inside the parenthesis pushed to it
void handleParenthesis(ListIterator& iter, TokenList& postExpr)
{
iter.advance();
getValue(iter, postExpr, false);
while (iter.tokenChar() != ')')
{
evalStep(iter, postExpr);
}
}
// evalStep
// Evaluates the current operator
// Parameters:
// iter - the iterator for the list of tokens
// postExpr - the postfix expression we are converting to
// Pre-condition: Next token is an operator (although, it will just advance if it isn't)
// Post-condition: All values related to this operation pushed to postExpr in the order dictated by postfix
// Iter is on the last token evaluated in this step (so iter.advance() next time will
// bring it to the next thing to be evaluated)
void evalStep(ListIterator& iter, TokenList& postExpr)
{
iter.advance();
switch (iter.tokenChar())
{
case '*':
case '/':
case '%':
handleMultiplyLevelOperation(iter, postExpr);
break;
case '+':
case '-':
handleAdditionLevelOperation(iter, postExpr);
break;
}
}
//The function takes in an iterator and TokenList and will rewrite numbers at the iterator's
//Pre- The position is located at a number or a parethesis
//Post- It will write to the postFix TokenList and update the iterator
void getValue(ListIterator &iter, TokenList &postFix)
{
//If parethesis are found this else if will rewrite the parenthesis in postFix
if (iter.tokenChar() == '(')
{
iter.advance();
getValue(iter, postFix);
iter.advance();
assignOp(iter, postFix);
}
//If the current position is an integer
else
{
postFix.push_back(iter.token());
}
}
// isNextOperatorMultiplication
// Checks if the next operation in the expression has multiplication precedence
// This is used to ensure multiplication is handled before addition
// Parameters:
// iter - the iterator for the list of tokens - not sent by reference, as in the other
// functions, so that we can look ahead without having to go back again.
// Pre-condition: Next token is an operator (although, if it's not, I suppose the next operation isn't
// technically multiplication)
// Return: whether the next operation is multiplication
bool isNextOperatorMultiplication(ListIterator iter)
{
bool isMultiplication;
iter.advance();
switch (iter.tokenChar())
{
case '*':
case '/':
case '%':
isMultiplication = true;
break;
default:
isMultiplication = false;
break;
}
return isMultiplication;
}
//This function will solve a postFix notation TokenList.
//Pre- This function takes in an iterator for a postFix TokenList and a TokenList in postFix notation.
//Post- It will return the result of the entire postFix notation.
int evalPost(ListIterator &iter, TokenList &postFix, VarTree &vt)
{
Token v1, v2;
int value = 0, n1, n2;
bool solved = false, solvedI = false;
char saveChar;
//Making the stack
TokenList toSolve;
//Runs until the equation is determined to be solved.
while (solved == false)
{
//Will add all the consecutive integers onto the stack
while (iter.tokenChar() != '=' && iter.tokenChar() != '+' && iter.tokenChar() != '-' && iter.tokenChar() != '*' && iter.tokenChar() != '/' && iter.tokenChar() != '%')
{
//Actually pushing onto the stack
toSolve.push_front(iter.token());
iter.advance();
}
//Getting 2 numbers from the stack
v2 = toSolve.pop_front();
v1 = toSolve.pop_front();
//If it a normal integer
if(v2.isInteger())
{
n2 = v2.integerValue();
}
//If it is a variable find it
else
{
n2 = vt.lookup(v2.tokenText());
}
//If it a normal integer
if(v1.isInteger())
{
n1 = v1.integerValue();
}
//If it is a variable find it
else
{
n1 = vt.lookup(v1.tokenText());
}
//Grabbing the character operation from the originol TokenList
saveChar = iter.tokenChar();
iter.advance();
if(saveChar == '+')
{
value = n1 + n2;
}
else if(saveChar == '-')
{
value = n1 - n2;
}
else if(saveChar == '*')
{
value = n1 * n2;
}
else if(saveChar == '/')
{
value = n1 / n2;
}
else if(saveChar == '%')
{
value = n1 % n2;
}
else if(saveChar == '=')
{
vt.assign(v1.tokenText(), n2);
value = n2;
}
//Checks if the equation is done
if(toSolve.empty() && !(iter != postFix.end()))
{
solved = true;
}
//If the equation is not done you push the current result and loop
else
{
toSolve.push_front(Token(value));
}
}
return value;
}
