i have postfix calculator, but he is not working, can you please help me?
I want calculate postfix expression 2 sin 2 cos / 5 *
Output is 5.000000, but correct output is 0.17...
Calculations work!
I think the problem is somewhere in adding expressions to the stack.
Thank you for any advice!
const char *arrayPostfix[1000];
//.
//.
//.
//Filling the field
//field contents:
//2 <SIN> 2 <COS> </> 5 <*>
const char *stack[1000];
int counter = 0;
int i;
int numberofElement = 7; // the number of elements - 2 <SIN> 2 <COS> </> 5 <*>
char myString[100];
double help;
for (i = 0; i < numberofElement; i++) {
if (arrayPostfix[i][0] != '<') {
// IS A NUMBER
stack[counter] = arrayPostfix[i];
counter++;
} else {
// IT ISNT NUMBER
//// GET LAST OPERATOR - typedef struct
// this works
operator lastOperator;
int x = 0;
for (x = 0; x < sizeof(operatory) / sizeof(operator); x++) {
if (strcmp(arrayPostfix[i], operatory[x].nazev) == 0) {
lastOperator = operatory[x];
break;
}
}
// Operators are ok..
double n1, n2;
if (lastOperator.numberofOperators == 2) {// a+b, a-b, a*b, a/b
counter--;
n1 = atof(stack[counter]);//string to double
counter--;
n2 = atof(stack[counter]);//string to double
help = lastOperator.funkce_dvaOperator(n2, n1); // this works, calculate
sprintf(myString, "%f", help); //double to string
stack[counter] = myString;
counter++;
} else { // sin(a), cos(a)....
counter--;
n1 = atof(stack[counter]); //string to double
help = lastOperator.funkce_jedenOperator(n1); // this works, calculate
sprintf(myString, "%f", help); //double to string
stack[counter] = myString;
counter++;
}
}
return atof(stack[0]);
}
steps:
1) add number 2
--------------------------------------------
Index [ 0 ] je : 2
--------------------------------------------
2) calculate sin(2)
--------------------------------------------
Index [ 0 ] je : 0.034899
--------------------------------------------
3) add number 2 - but in stac [0] is fail value..why?
--------------------------------------------
Index [ 0 ] je : 0.034899
Index [ 1 ] je : 0.034899
This here is a very big problem:
sprintf(myString, "%f", help); //double to string
stack[counter] = myString;
Here you set the pointer in stack[counter] to point to myString. But you forget that myString will always be the same pointer, so whenever you change myString all entries in stack that points to myString will be changed as it is all the same string.