I am attempting to build a parenthesis checker in C using a homebuilt stack, but the stack is an array that prevents my program from working by returning an array of random numbers. Please assist.
#define STACK_SIZE 100
#include <stdio.h>
char stack[STACK_SIZE];
int sp=0;
/*
* Pushes character c onto the stack.
* Returns 0 if successful.
* Returns -1 if an error occurs. (Stack full).
*/
int push (char c)
{
if (sp >= STACK_SIZE) {
printf("c");
return -1;
}
else {
stack[sp] = c;
sp++;
return 0;
}
}
/*
* Pops next character off the stack.
* Returns the char if successful.
* Returns -1 if an error occurs. (Stack empty).
*/
int pop ()
{
if (sp == 0) {
return -1;
}
else {
sp--;
return stack[sp];
}
}
/*
* Returns the current size of the stack.
*/
int stackSize()
{
printf("%i", sp);
return sp;
}
void printStack()
{
//TODO
}
int main ()
{
int i;
for (i = 0; i < 100; i++) {
stack[i] = 0;
}
int null = 0;
char b;
char a = getchar();
while (a != EOF) {
if (a == '(') {
if (stackSize() >= 100) {
printf("Error. Stack Full!\n");
return -1;
}
push(')');
}
else if (a == '{') {
if (stackSize() >= 100) {
printf("Error. Stack Full!\n");
return 1;
}
push('}');
}
else if (a == '[') {
if (stackSize() >= 100) {
printf("Error. Stack Full!\n");
return 1;
}
push(']');
}
else if (a == ')') {
b = pop();
if (stackSize() == 0) {
printf("Found %c. No matching character\n", a);
return 2;
}
else if (a != b) {
printf("Found %c, expected ).\n", a);
return 2;
}
}
else if (a == '}') {
b = pop();
if (stackSize() == 0) {
printf("Found %c. No matching character\n", a);
return 2;
}
else if (a != b) {
printf("Found %c, expected }.\n", a);
return 2;
}
}
else if (a == ']') {
b = pop();
if (stackSize() == 0) {
printf("Found %c. No matching character\n", a);
return 2;
}
else if (a != b) {
printf("Found %c, expected ].\n", a);
return 2;
}
}
}
if (stackSize() != 0) {
printf("Expecting %c, found end of input.\n", a);
return 3;
}
printf("Well formatted input.\n");
return 4;
}
Once I use a file as input, the program spits out roughly 100 random numbers and the "Error. Stack Full!" message. I can not get around this. Any help is welcomed and would be greatly appreciated. Thank you!
Related
below is the code of infix to postfix conversion using stack.The code executes an infinite loop printing stack underflow in one of the pop function ,i have tried commenting pop function call in right paranthesis loop but then there is no output, i am unable to find which pop function creates this problem . if anyone could help me find what the problem is it would be appreciated.
P.S. - The code works fine if i remove parenthesis from the infix equation that i am passing.
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
struct stack{
int size;
int top;
char *arr;
};
void display(struct stack *ptr)
{
if(ptr->top == -1)
{
printf("Stack is Empty");
}
else
{
for(int i = ptr->top ; i>=0 ; i--)
{
printf("Element: %d\n",ptr->arr[i]);
}
}
}
int isEmpty(struct stack *ptr)
{
if(ptr->top == -1)
{
return 1;
}
else
{
return 0;
}
}
int isFull(struct stack *ptr)
{
if(ptr->top == ptr->size - 1)
{
return 1;
}
else
{
return 0;
}
}
void push(struct stack *ptr,int data)
{
if(isFull(ptr))
{
printf("Stack Overflow");
}
else
{
ptr->top = ptr->top + 1;
ptr->arr[ptr->top] = data;
}
}
char pop(struct stack *ptr)
{
if(isEmpty(ptr))
{
printf("Stack Underflow");
return 0;
}
else
{
char ch = ptr->arr[ptr->top];
ptr->top = ptr->top - 1;
return ch;
}
}
char stackTop(struct stack *ptr)
{
return ptr->arr[ptr->top];
}
int isOperator(char a)
{
if(a == '+'|| a == '-'|| a == '*'|| a == '/')
{
return 1;
}
else
{
return 0;
}
}
int precedence(char a)
{
if(a == '*' || a == '/')
{
return 3;
}
else if(a == '+' || a == '-')
{
return 2;
}
else
{
return -1;
}
}
char* infix_postfix(char *infix)
{
struct stack *sp = (struct stack *) malloc(sizeof(struct stack));
sp->size = 100;
sp->top = -1;
sp->arr = (char *) malloc(sp->size * sizeof(char));
char *postfix = (char *) malloc((strlen(infix+1)) * sizeof(char));
int i=0;
int j=0;
while(infix[i] != '\0')
{
if(infix[i] == '(')
{
push(sp,infix[i]);
i++;
}
else if(infix[i] == ')')
{
while(!(isEmpty(sp)) && stackTop(sp) != '(')
{
postfix[j] = pop(sp);
j++;
}
pop(sp);
}
else if(!isOperator(infix[i]))
{
postfix[j] = infix[i];
i++;
j++;
}
else
{
while(!(isEmpty(sp)) && precedence(infix[i])<=precedence(stackTop(sp)))
{
postfix[j] = pop(sp);
j++;
}
push(sp,infix[i]);
i++;
}
}
while(!isEmpty(sp))
{
postfix[j] = pop(sp);
j++;
}
postfix[j] = '\0';
return postfix;
}
int main(void)
{
char *infix = "(x-y/z-k*d)";
printf("postfix is %s",infix_postfix(infix));
return 0;
}
Code stuck on ')'.
Adding a i++; somewhere in the else if(infix[i] == ')') { .... } block resulted in below. Else code continues to parse ')'.
postfix is xyz/-kd*-
How bug was found:
Added a debug print.
while (infix[i] != '\0') {
printf("Infix: %d %c\n", infix[i], infix[i]); // added
That led to see code stuck when ')' was parsed.
Below is the code for infix to prefix conversion. My code works fine until the use of reverse function where it does not print any string after copying. I have tried using a for loop to copy the reversed string but the outcome remains the same and the program terminates without giving proper output. Print statements in the reverse function work before copying but not after that. Could anyone let me know where the problem is?
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
struct stack{
int size;
int top;
char *arr;
};
void display(struct stack *ptr)
{
if(ptr->top == -1)
{
printf("Stack is Empty");
}
else
{
for(int i = ptr->top ; i>=0 ; i--)
{
printf("Element: %d\n",ptr->arr[i]);
}
}
}
int isEmpty(struct stack *ptr)
{
if(ptr->top == -1)
{
return 1;
}
else
{
return 0;
}
}
int isFull(struct stack *ptr)
{
if(ptr->top == ptr->size - 1)
{
return 1;
}
else
{
return 0;
}
}
void push(struct stack *ptr,int data)
{
if(isFull(ptr))
{
printf("Stack Overflow");
}
else
{
ptr->top = ptr->top + 1;
ptr->arr[ptr->top] = data;
}
}
char pop(struct stack *ptr)
{
if(isEmpty(ptr))
{
printf("Stack Underflow");
return 0;
}
else
{
char ch = ptr->arr[ptr->top];
ptr->top = ptr->top - 1;
return ch;
}
}
char stackTop(struct stack *ptr)
{
return ptr->arr[ptr->top];
}
int isOperator(char a)
{
if(a == '+'|| a == '-'|| a == '*'|| a == '/')
{
return 1;
}
else
{
return 0;
}
}
int precedence(char a)
{
if(a == '*' || a == '/')
{
return 3;
}
else if(a == '+' || a == '-')
{
return 2;
}
else
{
return -1;
}
}
char * reverse(char exp[])
{
int l = strlen(exp);
int j = 0;
char temp[l];
for(int i=l-1;i>=0;i--,j++)
{
temp[j] = exp[i];
}
temp[j] = '\0';
printf("prefix is %s",temp);
strcpy(exp,temp);
// for(int i=0;i<=l;i++)
// {
// exp[i] = temp[i];
// }
printf("prefix is %s",exp);
return exp;
}
char * infix_prefix(char *infix)
{
struct stack *sp = (struct stack *) malloc(sizeof(struct stack));
sp->size = 100;
sp->top = -1;
sp->arr = (char *) malloc(sp->size * sizeof(char));
char *prefix = (char *) malloc((strlen(infix+1)) * sizeof(char));
infix = reverse(infix);
int i=0;
int j=0;
while(infix[i] != '\0')
{
if(infix[i] == ')')
{
push(sp,infix[i]);
i++;
}
else if(infix[i] == '(')
{
while(!isEmpty(sp) && stackTop(sp) != ')')
{
prefix[j] = pop(sp);
j++;
}
if(!isEmpty(sp))
{
pop(sp);
i++;
}
else
{
printf("Incorrect Expression");
exit(0);
}
}
else if(!isOperator(infix[i]))
{
prefix[j] = infix[i];
i++;
j++;
}
else if(isOperator(infix[i]))
{
while(!isEmpty(sp) && precedence(infix[i])<=precedence(stackTop(sp)))
{
prefix[j] = pop(sp);
j++;
}
push(sp,infix[i]);
i++;
}
else
{
printf("Incorrect expression");
exit(0);
}
}
while(!isEmpty(sp) && stackTop(sp) != '(')
{
prefix[j] = pop(sp);
j++;
}
if(stackTop(sp) == ')')
{
printf("Incorrect expression");
exit(0);
}
prefix = reverse(prefix);
prefix[j] = '\0';
return prefix;
}
int main(void)
{
char *infix = "(x-y/z-k*d)";
printf("prefix is %s",infix_prefix(infix));
return 0;
}
The reverse indeed has a problem: the temp array is defined with a length of l: that's not long enough to store the null terminator at temp[j] after the loop, causing undefined behavior.
There are more problems:
char *prefix = (char *) malloc((strlen(infix+1)) * sizeof(char)); does not allocate enough space for a copy of infix. You should write char *prefix = malloc(strlen(infix) + 1);
infix = reverse(infix); will crash because the argument to infix_prefix is a string literal which must not be modified. You should declare the argument as const char *infix and make a modifiable copy with strdup() if reversing is really needed, which I doubt very much.
Here is a modified version of reverse that performs the reverse operation in place:
char *reverse(char exp[]) {
int i = 0;
int j = strlen(exp);
while (j-- > i) {
char c = exp[j];
exp[j] = exp[i];
exp[i++] = c;
}
return exp;
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct stack {
int size;
int top;
char *arr;
};
int isEmpty(struct stack *ptr) {
if (ptr->top == -1)
{
return 1;
}
else
{
return 0;
}
}
int isFull(struct stack *ptr) {
if (ptr->top == ptr->size - 1)
{
return 1;
}
else
{
return 0;
}
}
int push(struct stack *ptr, int val) {
if (isFull(ptr))
{
return -1;
}
else
{
ptr->top++;
ptr->arr[ptr->top] = val;
}
return 1;
}
int pop(struct stack *ptr) {
if (isEmpty(ptr))
{
return -1;
}
else
{
ptr->top--;
int val = ptr->arr[ptr->top];
return val;
}
}
int stackTop(struct stack *ptr) {
return ptr->arr[ptr->top];
}
int precedence(char ch) {
if (ch == '/' || ch == '*')
{
return 3;
}
else if (ch == '+' || ch == '-')
{
return 2;
}
else
{
return 0;
}
}
int isOperand(char ch) {
if (ch == '+' || ch == '-' || ch == '/' || ch == '*')
{
return 1;
}
else
{
return 0;
}
}
char IntoPostFix(char *Infix) {
struct stack *s = (struct stack *)malloc(sizeof(struct stack));
s->top = -1;
s->size = 100;
s->arr = (char *)malloc(s->size * sizeof(char));
char *postfix = (char *)malloc(strlen(Infix + 1) * sizeof(char));
int i = 0; //value at intfix;
int j = 0; //store into post fix
while (Infix[i] != '\0')
{
if (!isOperand(Infix[i]))
{
postfix[j] = Infix[i];
i++;
j++;
}
else
{
if (precedence(Infix[i]) > precedence(stackTop(s)))
{
push(s, Infix[i]);
i++;
}
else
{
postfix[j] = pop(s);
j++;
}
}
}
while (!isEmpty(s))
{
postfix[j] = pop(s);
j++;
}
postfix[j] = '\0';
return postfix[j];
}
int main() {
char *Infix = "a-b";
printf("PostFix is : %s\n ", IntoPostFix(Infix));
return 0;
}
You format string expects a string but you give it a char:
printf("PostFix is : %s\n ", IntoPostFix(Infix));
Change the signature and return postfix instead of the '\0':
char *IntoPostFix(char *Infix) {
...
return postfix;
}
It now prints "ab\n ", that is, we correctly process 'a', 'b', and '-' is pushed on the stack. pop(s) return 0 you decrement top before you return the value:
ptr->top--;
int val = ptr->arr[ptr->top];
return val;
instead do:
return ptr->arr[ptr->top--];
and voila:
PostFix is : ab-
Bonus round:
In IntoPostFix you call malloc() 3 times and don't call free() so your program leaks memory.
Instead of strlen(Infix + 1) which evaluates to strlen(Infix) - 1 you want strlen(Infix) + 1.
Instead of while (Infix[i] != '\0') consider using a for() loop to reduce the scope of the variable i. Avoid negation and use continue for less branching noise. If you use this style of compressing newlines you get about twice as much code on the screen at a time:
for(int i = 0; Infix[i]; ) {
if(isOperand(Infix[i])) {
if(precedence(Infix[i]) > precedence(stackTop(s))) {
push(s, Infix[i++]);
} else {
postfix[j++] = pop(s);
}
continue;
}
postfix[j++] = Infix[i++];
}
I'm writing a Calculator in C from scratch (homework assignment) and have troubles with memory somewhere.. The algorithm works perfectly, but I'm getting a set of Valgrind errors/warnings, e.g.:
echo -n "1" | valgrind ./a.out --track-origins=yes
==14261== Conditional jump or move depends on uninitialised value(s)
==14261== at 0x400B9F: create_rpn (main.c:53)
==14261== by 0x400742: main (main.c:253)
My makefile:
all:
gcc main.c -g -O2 -Wall -Werror -std=c99
My source code is below (and on GitHub). Can you help with it? Thank you in advance!
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_LEN 1024
// needs to check priority
int get_power(char op) {
if (op == '+') {
return 2;
} else if (op == '-') {
return 2;
} else if (op == '*') {
return 4;
} else if (op == '/') {
return 4;
} else {
return 0;
}
}
// checks if current char is operator
int is_operator(char op) {
if (op == '+' || op == '-' || op == '*' || op == '/') {
return 1;
} else {
return 0;
}
}
// checks if current char is digit
int is_digit(char op) {
if ((op >= '0' && op <= '9') || op == '.') {
return 1;
} else {
return 0;
}
}
// evaulates array in Postfix
double evaulate_rpn(char** exp, size_t len) {
double* stack = (double* ) malloc(len*sizeof(double)); // stack for operands
double a1 = 0.0;
double a2 = 0.0; // buffers to save stack items
size_t place = 0; // current stack size
for (size_t i = 0; i < len; ++i) {
if (is_operator(*exp[i]) == 1) {
// takes out last 2 operands, processes
if (place > 1) {
a1 = stack[place - 2];
a2 = stack[place - 1];
if (strncmp(exp[i], "+", 1) == 0) {
stack[place - 2] = a1 + a2;
} else if (strncmp(exp[i], "-", 1) == 0) {
stack[place - 2] = a1 - a2;
} else if (strncmp(exp[i], "*", 1) == 0) {
stack[place - 2] = a1 * a2;
} else if (strncmp(exp[i], "/", 1) == 0) {
stack[place - 2] = a1 / a2;
}
place -= 1;
} else if (place == 1) {
// unary minus, unary plus..
a1 = stack[place - 1];
if (strncmp(exp[i], "-", 1) == 0) {
stack[place - 1] = 0 - a1;
} else if (strncmp(exp[i], "+", 1) == 0) {
stack[place - 1] = a1;
}
} else {
// wrong order / anything else
printf("[error]");
exit(0);
}
} else {
// is operand -> convert char to double -> save double to stack
stack[place] = atof(exp[i]);
place++ ;
}
}
float res = stack[0];
free(stack);
return res; // result here
}
void push_to_stack(char*** reverse, size_t* inited_lines, size_t* used_lines, char* item, size_t size) {
if(*inited_lines <= *used_lines){
*inited_lines *= 2;
char** buf = (char** ) realloc(*reverse, (*inited_lines)*sizeof(char** ));
if (buf) {
*reverse = buf;
} else {
printf("[error]");
exit(0);
}
}
char* str = calloc(size + 1, sizeof(char));
if (str) {
memcpy(str, item, size + 1);
str[size] = '\0';
(*reverse)[*used_lines] = str;
(*used_lines)++ ;
} else {
printf("[error]");
exit(0);
}
}
// transform from Infix to Postfix notation
double create_rpn(char* exp, size_t len){
// stack of chars for operands ()+-*/
char* stack = (char* ) malloc(len);
if (stack == NULL) {
printf("[error]");
exit(0);
}
size_t stack_top = 0; // position of last item in stack
// array of numbers
size_t inited_lines = 1;
size_t used_lines = 0;
char** reverse = (char** ) malloc(inited_lines*sizeof(char* ));
if (reverse == NULL) {
printf("[error]");
exit(0);
}
char buffer = 0;
int bracket_deep = 0;
int digit = 0; // flag to start parsing Numbers/digits
size_t start_index = 0; // for parsing Long-Vals
size_t index = 0;
while (index <= len) {
buffer = exp[index]; // buffer constats only 1 char but it is a string
if (is_digit(buffer) == 1) {
// save first digit place
if (digit == 0) {
start_index = index;
digit = 1;
}
} else {
// push to stack when Num is over
if (digit == 1) {
digit = 0;
size_t size = index - start_index; // size of str
push_to_stack(&reverse, &inited_lines, &used_lines, exp + start_index, size);
}
// push Operands + check priority
if (is_operator(buffer) == 1) {
size_t power = get_power(buffer);
for (int i = stack_top - 1; i >= 0; --i) {
if (stack[i] == '(') {
break;
}
if (get_power(stack[i]) >= power) {
push_to_stack(&reverse, &inited_lines, &used_lines, &stack[i], 1);
stack_top-- ;
}
}
// push current Operand to stack
stack[stack_top++ ] = buffer;
} else if (buffer == '(') {
stack[stack_top++ ] = buffer;
bracket_deep++ ;
} else if (buffer == ')') {
// push operands to result
bracket_deep-- ;
stack_top-- ; // if no, '' will be added to output
while (stack[stack_top] != '(') {
push_to_stack(&reverse, &inited_lines, &used_lines, &stack[stack_top], 1);
if (stack_top > 0) {
stack_top-- ;
} else {
break;
}
}
} else if (buffer == ' ' || buffer == '\n') {
// ignore this case
} else if (buffer == '\0') {
for (int i = stack_top - 1; i >= 0; --i) {
push_to_stack(&reverse, &inited_lines, &used_lines, &stack[i], 1);
}
stack_top = 0;
} else {
printf("[error]"); // - wrong char: '%s', %c\n", buffer, *buffer); // wrong char!
exit(0);
}
}
if (bracket_deep < 0) {
printf("[error]"); // wrong bracket expr
exit(0);
}
index++ ;
}
free(stack);
if (bracket_deep == 0) {
double res = evaulate_rpn(reverse, used_lines);
for (int i = 0; i < inited_lines; i++) {
free(reverse[i]);
}
free(reverse);
return res;
} else {
printf("[error]"); // wrong brackets
exit(0);
}
}
int main() {
char* expression = (char* ) malloc(MAX_LEN*sizeof(char));
if (expression) {
size_t len = 0;
while (scanf("%c", &expression[len]) != -1) { // switch to getch ???
if (expression[len] != ' ') { // save everything except spaces
len++ ;
}
}
double result = create_rpn(expression, len);
printf("%.2f", result);
free(expression);
} else {
printf("[error]");
exit(0);
}
return 0;
}
You are reading 1 byte beyond the array bound, because your while loop in create_rpn() is
while (index <= len)
but should be
while (index < len)
/* ^ without the = */
since arrays are 0 indexed, exp[len] is beyond the array.
Also
Avoid redundant parentheses, they make the code ugly and hence, hard to read and understand.
Do not cast the return value of malloc(), read the link and you will understand why.
Another tip to make your code clearer, is to avoid mixing code with declarations, for a compiler it's easy to see a variable's scope, but not for the eyes.
So, essentially I have two files:
File 1:
//
// main.c
// frederickterry
//
// Created by Rick Terry on 1/15/15.
// Copyright (c) 2015 Rick Terry. All rights reserved.
//
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int size (char *g) {
int ofs = 0;
while (*(g+ofs) != '\0') {
++ofs;
}
return ofs;
}
int parse(char *g) {
// Setup
char binaryConnective;
int negated = 0;
// Looking for propositions
int fmlaLength = size(g);
if(fmlaLength == 0) {
return 1;
}
if(fmlaLength == 1) {
if(g[0] == 'p') {
return 1;
} else if (g[0] == 'q') {
return 1;
} else if (g[0] == 'r') {
return 1;
} else {
return 0;
}
}
// Now looking for negated preposition
if(fmlaLength == 2) {
char temp[100];
strcpy(temp, g);
if(g[0] == '-') {
negated = 1;
int negatedprop = parse(g+1);
if(negatedprop == 1) {
return 2;
}
}
}
// Checking if Binary Formula
char arrayleft[50];
char arrayright[50];
char *left = "";
char *right = "";
int numLeft = 0;
int numRight = 0;
int bclocation = 0;
int binarypresent = 0;
if(fmlaLength != 1 && fmlaLength != 2) {
if(g[0] == '-') {
int negatedBinary = parse(g+1);
if(negatedBinary == 1 || negatedBinary == 2 || negatedBinary == 3) {
return 2;
} else {
return 0;
}
}
int i = 0;
int l = 0;
int p = strlen(g);
for(l = 0; l < strlen(g)/2; l++) {
if(g[l] == '(' && g[p-l-1] == ')') {
i++;
}
}
for(int q = i; q < strlen(g); q++) {
if(g[q] == '(') {
numLeft++;
} else if(g[q] == ')') {
numRight++;
}
arrayleft[q] = g[q];
//printf("%c", arrayleft[i]);
//printf("%s", left);
if((numRight == numLeft) && (g[q+1] == 'v' || g[q+1] == '>' || g[q+1] == '^')) {
arrayleft[q+1] = '\0';
bclocation = q+1;
binaryConnective = g[q+1];
binarypresent = 1;
// printf("The binary connecive is: %c\n", binaryConnective);
break;
}
}
if(binarypresent == 0) {
return 0;
}
int j = 0;
for(int i = bclocation+1; i < strlen(g)-1; i++) {
arrayright[j] = g[i];
j++;
}
arrayright[j] = '\0';
left = &arrayleft[1];
right = &arrayright[0];
//printf("Printed a second time, fmla 1 is: %s", left);
int parseleft = parse(left);
// printf("Parse left result: %d\n", parseleft);
if(parseleft == 0) {
return 0;
}
int parseright = parse(right);
if(parseright == 0) {
return 0;
}
// printf("Parse right result: %d\n", parseleft);
if(negated == 1) {
return 2;
} else {
return 3;
}
}
return 0;
}
int type(char *g) {
if(parse(g) == 1 ||parse(g) == 2 || parse(g) == 3) {
if(parse(g) == 1) {
return 1;
}
/* Literals, Positive and Negative */
if(parse(g) == 2 && size(g) == 2) {
return 1;
}
/* Double Negations */
if(g[0] == '-' && g[1] == '-') {
return 4;
}
/* Alpha & Beta Formulas */
char binaryConnective;
int numLeft = 0;
int numRight = 0;
int bclocation = 0;
int binarypresent = 0;
int i = 0;
if(g[0] == '(') {
i++;
}
if(g[0] == '-') {
i++;
if(g[1] == '(') {
i++;
}
}
for(i; i < strlen(g); ++i) {
if(g[i] == '(') {
numLeft++;
} else if(g[i] == ')') {
numRight++;
}
if(numRight == numLeft) {
if(g[i+1] == 'v' || g[i+1] == '>' || g[i+1] == '^') {
bclocation = i+1;
binaryConnective = g[i+1];
binarypresent = 1;
break;
}
}
}
/* Connective established */
if(binaryConnective == '^') {
if(g[0] == '-') {
return 3;
} else {
return 2;
}
} else if(binaryConnective == '>') {
if(g[0] == '-') {
return 2;
} else {
return 3;
}
} else if (binaryConnective == 'v') {
if(g[0] == '-') {
return 2;
} else {
return 3;
}
}
}
return 0;
}
char bin(char *g) {
char binaryConnective;
char arrayLeft[50];
int numLeft = 0;
int numRight = 0;
int bclocation = 0;
int i = 0;
if(g[0] == '(') {
i++;
}
if(g[0] == '-') {
i++;
if(g[1] == '(') {
i++;
}
}
for(i; i < strlen(g); ++i) {
if(g[i] == '(') {
numLeft++;
} else if(g[i] == ')') {
numRight++;
}
int j = 0;
arrayLeft[j++] = g[i];
if(numRight == numLeft) {
if(g[i+1] == 'v' || g[i+1] == '>' || g[i+1] == '^') {
arrayLeft[i+1] = '\0';
bclocation = i+1;
binaryConnective = g[i+1];
return binaryConnective;
}
}
}
return binaryConnective;
}
char *partone(char *g) {
char binaryConnective;
char arrayLeft[50];
char arrayRight[50];
int numLeft = 0;
int numRight = 0;
int bclocation = 0;
int i = 0;
if(g[0] == '(') {
i++;
}
if(g[0] == '-') {
i++;
if(g[1] == '(') {
i++;
}
}
int j = 0;
for(i; i < strlen(g); ++i) {
if(g[i] == '(') {
numLeft++;
} else if(g[i] == ')') {
numRight++;
}
arrayLeft[j] = g[i];
if(numRight == numLeft) {
if(g[i+1] == 'v' || g[i+1] == '>' || g[i+1] == '^') {
arrayLeft[j+1] = '\0';
bclocation = i+1;
binaryConnective = g[i+1];
break;
}
}
j++;
}
int m = 0;
for(int k = bclocation+1; k < strlen(g)-1; k++) {
arrayRight[m] = g[k];
m++;
}
arrayRight[m] = '\0';
char* leftSide = &arrayLeft[0];
// printf("%s\n", leftSide);
// printf("%s\n", rightSide);
int k = 0;
k++;
return leftSide;
}
char *parttwo(char *g) {
char binaryConnective;
char arrayLeft[50];
char arrayRight[50];
int numLeft = 0;
int numRight = 0;
int bclocation = 0;
int i = 0;
if(g[0] == '(') {
i++;
}
if(g[0] == '-') {
i++;
if(g[1] == '(') {
i++;
}
}
int j = 0;
for(i; i < strlen(g); ++i) {
if(g[i] == '(') {
numLeft++;
} else if(g[i] == ')') {
numRight++;
}
arrayLeft[j] = g[i];
if(numRight == numLeft) {
if(g[i+1] == 'v' || g[i+1] == '>' || g[i+1] == '^') {
arrayLeft[j+1] = '\0';
bclocation = i+1;
binaryConnective = g[i+1];
break;
}
}
j++;
}
int m = 0;
int n = size(g) - 1;
if(g[strlen(g)-1] != ')') {
n++;
}
for(int k = bclocation+1; k < n; k++) {
arrayRight[m] = g[k];
m++;
}
arrayRight[m] = '\0';
char* leftSide = &arrayLeft[0];
char* rightSide = &arrayRight[0];
// printf("%s\n", leftSide);
// printf("%s\n", rightSide);
return rightSide;
}
char *firstexp(char *g) {
char* left = partone(g);
char leftArray[50];
int i = 0;
for(i; i < strlen(left); i++) {
leftArray[i] = left[i];
}
leftArray[i] = '\0';
char binConnective = bin(g);
int typeG = type(g);
if(typeG == 2) {
if(binConnective == '^') {
return &leftArray;
} else if(binConnective == '>') {
return &leftArray;
}
} else if(typeG == 3) {
if(binConnective == 'v')
return &leftArray;
}
char temp[50];
for(int i = 0; i < strlen(leftArray); i++) {
temp[i+1] = leftArray[i];
}
temp[0] = '-';
char* lefttwo = &temp[0];
if(typeG == 2) {
if(binConnective == 'v') {
return lefttwo;
}
} else if(typeG == 3) {
if(binConnective == '>' || binConnective == '^') {
return lefttwo;
}
}
return "Hello";
}
char *secondexp(char *g) {
// char binaryConnective = bin(g);
// char* right = parttwo(g);
// char rightArray[50];
// int i = 0;
// for(i; i< strlen(right); i++) {
// rightArray[i+1] = right[i];
// }
// rightArray[i] = '\0';
// int typeG = type(g);
// if(type(g) == 2) {
// if(binaryConnective == '^') {
// return &rightArray;
// }
// } else if(type(g) == 3) {
// if(binaryConnective == 'v' || binaryConnective == '>') {
// return &rightArray;
// }
// }
return "Hello";
}
typedef struct tableau tableau;
\
\
struct tableau {
char *root;
tableau *left;
tableau *right;
tableau *parent;
int closedbranch;
};
int closed(tableau *t) {
return 0;
}
void complete(tableau *t) {
}
/*int main(int argc, const char * argv[])
{
printf("Hello, World!\n");
printf("%d \n", parse("p^q"));
printf("%d \n", type("p^q"));
printf("%c \n", bin("p^q"));
printf("%s\n", partone("p^q"));
printf("%s\n", parttwo("p^q"));
printf("%s\n", firstexp("p^q"));
printf("Simulation complete");
return 0;
}*/
File 2:
#include <stdio.h>
#include <string.h> /* for all the new-fangled string functions */
#include <stdlib.h> /* malloc, free, rand */
#include "yourfile.h"
int Fsize = 50;
int main()
{ /*input a string and check if its a propositional formula */
char *name = malloc(Fsize);
printf("Enter a formula:");
scanf("%s", name);
int p=parse(name);
switch(p)
{case(0): printf("not a formula");break;
case(1): printf("a proposition");break;
case(2): printf("a negated formula");break;
case(3): printf("a binary formula");break;
default: printf("what the f***!");
}
printf("\n");
if (p==3)
{
printf("the first part is %s and the second part is %s", partone(name), parttwo(name));
printf(" the binary connective is %c \n", bin(name));
}
int t =type(name);
switch(t)
{case(0):printf("I told you, not a formula");break;
case(1): printf("A literal");break;
case(2): printf("An alpha formula, ");break;
case(3): printf("A beta formula, ");break;
case(4): printf("Double negation");break;
default: printf("SOmewthing's wrong");
}
if(t==2) printf("first expansion fmla is %s, second expansion fmla is %s\n", firstexp(name), secondexp(name));
if(t==3) printf("first expansion fmla is %s, second expansion fmla is %s\n", firstexp(name), secondexp(name));
tableau tab;
tab.root = name;
tab.left=0;
tab.parent=0;
tab.right=0;
tab.closedbranch=0;
complete(&tab);/*expand the root node then recursively expand any child nodes */
if (closed(&tab)) printf("%s is not satisfiable", name);
else printf("%s is satisfiable", name);
return(0);
}
If you look at the first file, you'll see a method called * firstexp(char * g).
This method runs perfectly, but only if another method called * secondexp(char * g) is commented out.
If * secondexp(char * g) is commented out, then *firstexp runs like this:
Enter a formula:((pvq)>-p)
a binary formula
the first part is (pvq) and the second part is -p the binary connective is >
A beta formula, first expansion fmla is -(pvq), second expansion fmla is Hello
((pvq)>-p) is satisfiableProgram ended with exit code: 0
otherwise, if *secondexp is not commented out, it runs like this:
Enter a formula:((pvq)>-p)
a binary formula
the first part is (pvq) and the second part is -p the binary connective is >
A beta formula, first expansion fmla is \240L, second expansion fmla is (-
((pvq)>-p) is satisfiable. Program ended with exit code: 0
As you can see, the outputs are completely different despite the same input. Can someone explain what's going on here?
In the commented-out parts of secondexp and in parttwo, you return the address of a local variable, which you shouldn't do.
You seem to fill a lot of ad-hoc sized auxiliary arrays. These have the problem that they might overflow for larger expressions and also that you cannot return them unless you allocate them on the heap with malloc, which also means that you have to free them later.
At first glance, the strings you want to return are substrings or slices of the expression string. That means that the data for these strings is already there.
You could (safely) return pointers into that string. That is what, for example strchr and strstr do. If you are willing to modify the original string, you could also place null terminators '\0' after substrings. That's what strtok does, and it has the disadvantage that you lose the information at that place: If you string is a*b and you modify it to a\0b, you will not know which operator there was.
Another method is to create a struct that stores a slice as pointer into the string and a length:
struct slice {
const char *p;
int length;
};
You can then safely return slices of the original string without needing to worry about additional memory.
You can also use the standard functions in most cases, if you stick to the strn variants. When you print a slice, you can do so by specifying a field width in printf formats:
printf("Second part: '%.*s'\n", s->length, s->p);
In your parttwo() function you return the address of a local variable
return rightSide;
where rightSide is a pointer to a local variable.
It appears that your compiler gave you a warning about this which you solved by making a pointer to the local variabe arrayRight, that may confuse the compiler but the result will be the same, the data in arrayRight will no longer exist after the function returns.
You are doing the same all over your code, and even worse, in the secondexp() function you return a the address of a local variable taking it's address, you are not only returning the address to a local variabel, but also with a type that is not compatible with the return type of the function.
This is one of many probable issues that your code may have, but you need to start fixing that to continue with other possible problems.
Note: enable extra warnings when compiler and listen to them, don't try to fool the compiler unless you know exactly what you're doing.