Thread: Expression Manipulator v0.1

Could you provide a short code example showing how it is used?

after it is compiled, run it, and type in an expression:

Code:

9x^2+b

and it will parse it into objects and print it back out again. If there's a way to simplify it, it will do that automatically. ie:

Code:

9(x+3)^2

9x^2 + 54x + 81

note: minus signs must have a space after them, otherwise they'll be counted as negative signs

For examples of its use in code, look at int main()
(located in expression.cpp)

Ahh, I missed the main() function.

These are the changes I had to make to make the code compile in MSVC++.NET:

Added lines to Expression.h

Code:

#include <algorithm>
#include <cmath>
using std::sort;
using std::cos;
using std::sin;
using std::tan;
using std::log;
#include <limits>
namespace
{
    const double INFINITY = std::numeric_limits<double>::infinity();
}

Added lines to Expression.cpp

Code:

const double Float::EPSILON = 0.0000000000001; //double is not an integral type -- inline definition not possible

I also had to add return *this at numerous places where it had been omitted.
At one place (Term::return_first_factor()) I couldn't add "return *this" so I added a throw-statement instead.

Now I'll try the program.

The simplifying seem to work, I've tested it with some expressions.

If the string "(5)" is entered, the output will not be the same as if "5" is entered, but it could be me not understanding the output.

You're right... I didn't notice that. That's a bug.

Here is the executable:

//edit: another note: make sure there is a '*' between a variable and a parentheses. ie:

Code:

f(x)

will be interpreted as the function 'f' with parameter 'x'.

Code:

f*(x)

is f * x.

It has the wrong output for (x-y)^2

Whoops. Nevermind. Forgot about the whole 'space after a minus sign' thing.

this is WAYYYYY better then i thought it would be!!!!!

great job man!!

Originally posted by vasanth
Can u post the binary please.. could not compile the file

He did at the end of his last post.

Nice. A few thoughts/bugs:

1) Why is the result printed 4 times? I also noticed that (sometimes) the last two were the 'reverse' of the first two.
Did you use different methods of simplifying the expression, or?

5 + x = 5 + x
5 + x = 5 + x
x + 5 = x + 5
x + 5 = x + 5


2) Sometimes a "+0" or a "*1" is inserted:

Input: (x) = z

x = z
x = z
x + 0 = z
x + 0 = z

Input: f(x) = (f(x + h) - f(x)) / h

f(x) = 1*f([x + h]) + -f(x)*h
f(x) = 1*f([x + h]) + -f(x)*h
f(x) = 0+f([x + h]) + -f(x)*h
f(x) = 0+f([x + h]) + -f(x)*h


Otherwise it seems to work ok.

Yeah, you should enhance your parser.

x(y+z)
x*-y
(a+b)(c+d)

should be possible

x*(y+z)
x*-y works fine.
(a+b)*(c+d)