/// <summary>
/// This method immediatly calles the "Expression function"
/// </summary>
/// <param name="st"></param>
/// <param name="store"></param>
/// <returns></returns>
private static Sexpr assignment(Tokenizer st, Hashtable store)
{
Sexpr ans = expr(st, store); //Calling the expr function
st.NextToken(); //Next token
if (st.getString().Equals("=")) //If the next token equals "=" the function will call the next token and store the number assigned to the letter earlier recognized in the hashtable store.
{
st.NextToken();
if (!st.isNumber())
{
try
{
ans = new Assignment(ans, new Variable(st.getString()));
st.NextToken();
}
catch
{
}
}
else
{
throw new ArithmeticException("Obs!! endast bokstäver kan tilldelas värden");
}
}
else
{
st.PushBack();
return ans;
}
st.PushBack();
return ans;
}
private static Sexpr factor(Tokenizer st, Hashtable store)
{
Sexpr ans = prim(st, store);
st.NextToken();
while(st.getString() == "")
{
st.NextToken();
if (!st.isNumber())
ans = new Diff(ans, prim(st, store));
else
throw new ArgumentException("Nothing to apply the differentiate operator on");
}
st.PushBack();
return ans;
}
//Using this composition of function, that is, first expr and then term ensures that division and multiplication has higher priority over plus and minus.
private static Sexpr expr(Tokenizer st, Hashtable store)
{
Sexpr res = term(st, store);
st.NextToken();
while (st.isPlus() || st.isMinus())
{
if (st.isPlus())
{
res = new addition(res, term(st,store));
st.NextToken();
}
else if (st.isMinus())
{
res = new Subtraction(res, term(st, store));
st.NextToken();
}
}
st.PushBack();
return res;
}
private static Sexpr term(Tokenizer st, Hashtable store)
{
Sexpr res = factor(st, store);
st.NextToken();
while (st.isDiv() || st.isMult())
{
if (st.isMult())
{
res = new Mult(res,factor(st, store));
st.NextToken();
}
else if (st.isDiv())
{
res = new Div(res,factor(st, store));
st.NextToken();
}
}
st.PushBack();
return res;
}
private static Sexpr prim(Tokenizer st, Hashtable store)
{
st.NextToken();
Sexpr ans;
if (st.getString().Equals("("))
{
ans = assignment(st, store);
st.NextToken();
if (!st.getString().Equals(")"))
{
throw new ArgumentException("missing )");
}
}
else if (st.ToString() == "-")
{
ans = new Negation(prim(st, store));
return ans;
}
else if (st.ToString() == "&")
{
ans = new Eval(prim(st,store));
return ans;
}
else if (st.isNumber())
{
double v = st.GetNumber();
ans = new Constant(v);
return ans;
}
else if (!st.isNumber())
{
string id = st.getString();
st.NextToken();
if(st.getString()=="(")
{
st.PushBack();
if (id.Equals("sin"))
{
ans = new Sin(prim(st, store));
st.NextToken();
}
else if (id.Equals("cos"))
{
ans = new Cos(prim(st, store));
st.NextToken();
}
else if (id.Equals("exp"))
{
ans = new Exp(prim(st, store));
st.NextToken();
}
else if (id.Equals("log"))
{
ans = new Log(prim(st, store));
st.NextToken();
}
else
throw new ArgumentException("Incorrect function call");
}
else
ans = new Variable(id);
st.PushBack();
}
else
{
st.PushBack();
throw new ArgumentException("Incorrect function call or incorrect variable assignment");
}
return ans;
}
