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I am working on a calculator program. It is very simple (in
implementation, not use), but I am having trouble with getting input.
How can I take input and run it. I should note that I want all of the
math available in C++ to be available to the user (casting, shift,
etc.). Can anyone help me.
--
Here's the code:

#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <cmath>
#define newl "\n"
using namespace std;

int main(int argc, char *argv[]);

string i = "";

int main(int argc, char *argv[]){
cout << "? ";
cin >> i;
cout << i << newl;
cout << "";
getchar();
return 0;
}

AdvTHANKSance!

Max wrote:
> I am working on a calculator program. It is very simple (in
> implementation, not use), but I am having trouble with getting input.
> How can I take input and run it.

Not sure what you mean by "run it".

> I should note that I want all of the
> math available in C++ to be available to the user (casting, shift,
> etc.). Can anyone help me.

It's not as simple as you might want to think. Programming an interpreter
(that's what it sounds like) is a complicated task. I recommend starting
with Chapter 6 of TC++PL.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

On 2007-07-02 19:18, Max wrote:
> I am working on a calculator program. It is very simple (in
> implementation, not use), but I am having trouble with getting input.
> How can I take input and run it. I should note that I want all of the
> math available in C++ to be available to the user (casting, shift,
> etc.). Can anyone help me.
> --
> Here's the code:
>
> #include <cstdio>
> #include <cstdlib>

Do you use any of those?

> #include <iostream>
> #include <cmath>

Or this one?

> #define newl "\n"

Don't do that. C++ has the wonderful keyword const for just such things.
Replace with

const char newl = '\n';

> using namespace std;
>
> int main(int argc, char *argv[]);

You don't need a prototype of main.

>
> string i = "";

You have not included <string>.

> int main(int argc, char *argv[]){

If you don't plan to use the arguments then just 'int main()' will do
just fine.

> cout << "? ";
> cin >> i;
> cout << i << newl;
> cout << "";
> getchar();
> return 0;
> }

How simple is simple? The simplest reads in the operation first and then
asks for operands, which is easily implemented with a switch-statement.

--
Erik Wikström

"Max" write:

>I am working on a calculator program. It is very simple (in
> implementation, not use), but I am having trouble with getting input.
> How can I take input and run it. I should note that I want all of the
> math available in C++ to be available to the user (casting, shift,
> etc.). Can anyone help me.

I think you should back off and do some of the exercises in the first few
chapters of a C++ book before you do this.

> --
> Here's the code:
>
> #include <cstdio>
> #include <cstdlib>
> #include <iostream>

Choose an I/O method and use *it*, not two vastly differnt ways, C and C++

> #include <cmath>
> #define newl "\n"

Are you aware of the difference between a char and a string?

> using namespace std;
>
> int main(int argc, char *argv[]);

Why that complicated form? Why a prototype?

>
> string i = "";

string knows how to make a default ctor, use it.

> int main(int argc, char *argv[]){
> cout << "? ";
> cin >> i;

i is a very bad name for a sting. You can name a boy Shirley, but it is
still not a good idea.

> cout << i << newl;
> cout << "";

If you want a blank line, the usual way is to write

cout << '\n';

> getchar();
> return 0;
> }

Max wrote:

> I am working on a calculator program. It is very simple (in
> implementation, not use), but I am having trouble with getting input.
> How can I take input and run it.

It's not fully clear what your mean. Should your problem be to read a whole
line of input instead of just all characters to the next white space, then
you might want to read up on std::getline().

> I should note that I want all of the
> math available in C++ to be available to the user (casting, shift,
> etc.). Can anyone help me.

[snip]

> int main(int argc, char *argv[]);
>
> string i = "";

Why global?

>
> int main(int argc, char *argv[]){
> cout << "? ";
> cin >> i;

This will stop at the first white space.

while ( std::getline( std::cin, i ) ) {
}

will read whole lines of input one by one.

> cout << i << newl;
> cout << "";
> getchar();
> return 0;
> }


Best

Kai-Uwe Bux

Max wrote:
> How can I take input and run it.
> I should note that I want all of the
> math available in C++ to be available to the user (casting, shift,
> etc.). Can anyone help me.

You can't. C++ creates a binary. It doesn't create an interpreter.

There exist libraries which can do what you want, for example
this one: http://iki.fi/warp/FunctionParser/
However, if your understanding of C++ is minimal, it may be quite
a task to write a program which uses a library like that, even though
using it is relatively simple.

There's a simple example program on how to use the library there:

http://iki.fi/warp/FunctionParser/example.cc