c++ problem with function

tommycahir

hi all
i having a prob with this function i ment to take a linked list of gates that have been added and connected but when i try to get the value for second gate there is a read of an invalid address the structures are shown below as well
it read the first gate properly and carries out the simulation but when then second gate is read there is an error at
inputvalue = gatelist->Gate->connectorlist->ptr_to_connector->Value;

this for my 3rd year proj and any help would be greatly appreciated

int Simulation(GateList *gatelist)
{//open addgate
InputList* ValuesList = NULL;

int value,typenum = 0,inputvalue = 0;
char typegate[10];

while (gatelist != NULL)
{// open while
strcpy(typegate,gatelist->Gate->Type);

while(gatelist->Gate->connectorlist != NULL)
{ // check that the values are connected and that they value is accessible
inputvalue = gatelist->Gate->connectorlist->ptr_to_connector->Value;
InputList *newnode = NULL;
newnode = getInputList();
newnode->NextInput = NULL;
newnode->input = inputvalue;
newnode->NextInput = ValuesList;
ValuesList = newnode;
gatelist->Gate->connectorlist = gatelist->Gate->connectorlist->nextconnectorlist;
}
if (strcmp(typegate,"And")== 0)
typenum = 1;
else if (strcmp(typegate,"Or")== 0)
typenum = 2;
else if (strcmp(typegate,"Not")== 0)
typenum = 3;
else if (strcmp(typegate,"Nand")== 0)
typenum = 4;
else if (strcmp(typegate,"Nor")== 0)
typenum = 5;
else if (strcmp(typegate,"Xor")== 0)
typenum = 6;
else if (strcmp(typegate,"Xnor")== 0)
typenum = 7;
else
typenum = 8;
// choose which gate function that you need using the gate type
switch (typenum)
{ //open switch
case 1:
value = AndFunction(ValuesList);
//change and function
break;
case 2:
value = OrFunction(ValuesList);
break;
case 3:
value = NotFunction(ValuesList);
break;
case 4:
value = NandFunction(ValuesList);
break;
case 5:
value = NorFunction(ValuesList);
break;
case 6:
value = XorFunction(ValuesList);
break;
case 7:
value = XnorFunction(ValuesList);
break;
case 8:
Application->MessageBox(" unknown error !!! ", "Welcome to Logic Gate Simulator", MB_OKCANCEL + MB_DEFBUTTON1);
break;
}//close switch
if( gatelist->Gate->NextConnector != NULL)
gatelist->Gate->NextConnector->Value = value;

gatelist = gatelist->NextGate;
}// close while
return(value);
}


struct Connector_node{

int Value; // value on the line
struct Connectorlist *ptr_to_gate; //pointer to a node of connectorlist
struct Connector_node *nextPtr; // pointer to the next connector type in the linked list
};

struct Connectorlist{

struct Connectorlist *nextconnectorlist; // pointer to the next connector type in the linked list
struct Connector_node *ptr_to_connector; // pointer to the next connector type in the linked list
};

struct Gate_node{

int XPos; // location of the gate (i.e node) on the screen
int YPos; // location of the gate (i.e node) on the screen
int NumInputs; // number of inputs to the gate
char Type[10]; // type of gate
struct Connector_node *NextConnector; // the pointer to the next connector node
Connectorlist *connectorlist; // the pointer to the connectorlist
};

struct GateList{

struct Gate_node *Gate; // pointer to the gate
struct GateList *NextGate; // pointer to next
};

struct InputList{
int input; // input value
struct InputList *NextInput; // pointer to next input
};

tanx

hussey

You are checking this value :
while(gatelist->Gate->connectorlist != NULL)

you are not checking this
gatelist->Gate->connectorlist->ptr_to_connector->Value;

ptr_to_connector could be null??
value might not be set correctly??

Not 100% sure, what error are you getting

tommycahir

hi hussey i got an answer from another forum tanx for the help the error was that it kept trying to read an address that wasnt valid. got the whole thing running cos of that now only have to read and write a full data structure to file !!! any good sites that might help with this would be appreciated..
tanx for the help

issch

How come you use a switch statement to choose which function to call rather than calling them from your if statements?

tommycahir

actually that what i have done since i posted this what i had there was only a rough model i have tided up the code since then.