int parse(char *g)
/* returns 0 for non-formulas, 1 for atoms, 2 for negations, 3 for binary connective fmlas, 4 for existential and 5 for universal formulas.*/
{
//0:check for number of brackets
int counter = 0;
int i;
int length = strlen(g);
for(i = 0 ; i < length ; i++){
if(g[i] == '('){
counter++;
}
else if(g[i] == ')'){
counter--;
}
}
// case where it is an atomic formula
if(g[0] == 'X'){
if(g[1] == '['){
if(g[2] == 'x' || g[2] == 'y' || g[2] == 'z'){
if(g[3] == 'y' || g[3] == 'z' || g[3] == 'x'){
if(g[4] == ']'){
if(g[5] == '\0'){
return 1;
}
}
}
}
}
}
//2:case of negation
else if(g[0] == '-'){
if(g[1] != '\0'){
if(parse(g+1)>0){
return 2;
}
}
}
//4:case of Existential formula
else if(g[0] == 'E'){
if(g[1] == 'x' || g[1] == 'y' || g[1] == 'z'){
if(g[2] != '\0' && parse(g+2)>0){
return 4;
}
}
}
//5:case of Universal formula
else if(g[0] == 'A'){
if(g[1] == 'x' || g[1] == 'y' || g[1] == 'z'){
if(g[2] != '\0' && parse(g+2)>0){
return 5;
}
}
}
//3:case of Binary connective formula
else if(g[0] == '('){
// puts("in binary connective");
if(counter == 0){
// puts("counter check passed");
// printf("part one is: %s\n", partone(g));
// printf("part two is: %s\n", parttwo(g));
// printf("part one parse result: %d\n", parse(partone(g)));
// printf("part two parse result: %d\n", parse(parttwo(g)));
if(parse(partone(g)) > 0 && parse(parttwo(g)) > 0){
// puts("is binary connective");
return 3;
}
}
}
//A fail case to catch all the failures
return 0;
}
int main()
{
/*Input a string and check if its a 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("An atomic formula");break;
case 2: printf("A negated formula");break;
case 3: printf("A binary connective formula");break;
case 4: printf("An existential formula");break;
case 5: printf("A universal formula");break;
default: printf("Not a formula");break;
}
if (p==3)
{printf("The first part is %s, the binary connective is %c, the second part is %s", partone(name), bin(name), parttwo(name));
return(1);
}
int eval(char *nm, int edges[no_edges][2], int size, int V[3])
/*this method takes a formula, the list of edges of a graph, the number of vertices and a variable assignment. It then evaluates the formula and returns 1 or 0 as appropriate. */
{
int i, first, second;
char bin = nm[getConnectiveIndex(nm)];
char *before = partone(nm);
char *after = parttwo(nm);
switch(parse(nm))
{
case(1)://Atomic formula
first = getVariable(nm[2],V);
second = getVariable(nm[3],V);
if(is_edge(first,second,edges) == 1){
return 1;
}
else return 0;
break;
case(2)://negation formula
if(eval(nm+1,edges,size,V) == 0){
return 1;
}
else return 0;
break;
case(3)://Binary connective formula
switch(bin){
case 'v' :if(eval(before,edges,size,V) == 1 || eval(after,edges,size,V) == 1){
return 1;
}
else return 0;
case '^' :if(eval(before,edges,size,V) == 1 && eval(after,edges,size,V) == 1){
return 1;
}
else return 0;
case '>' :if(eval(before,edges,size,V) == 1){
if(eval(after,edges,size,V) == 1){
// puts("second part passed");
return 1;
}
else return 0;
}
else return 1;
}
break;
case(4)://Existential formula
for(i = 0 ; i < no_nodes ; i++){
switch(nm[1]){
case 'x': V[0] = i; break;
case 'y': V[1] = i; break;
case 'z': V[2] = i; break;
default: return -1;
}
if(eval(nm+2,edges,size,V) == 1){
return 1;
}
}
return 0;
break;
case(5)://Universal formula
for(i = 0 ; i < no_nodes ; i++){
switch(nm[1]){
case 'x': V[0] = i; break;
case 'y': V[1] = i; break;
case 'z': V[2] = i; break;
default: return -1;
}
if(eval(nm+2,edges,size,V) == 0){
return 0;
}
}
return 1;
break;
default: return -1;
}
}
