During our compiler's intermediate code generation phase, and more specifically while testing the arithmetic expressions and assignment rules, I noticed that although the respective quads are constructed successfully, when printing them out sometimes we'll get a bad_alloc exception. After tracing it, it looks like it's cause by the printQuads() method and specifically the following string access of key:
if(q.result != nullptr && q.result->sym != nullptr) {
cout << "quad " << opcodeStrings[q.op] << " inside if key check for" << opcodeStrings[q.op] << endl;
resultKey = q.result->sym->key;
}
I'll try to include the code that's relevant instead of dumping 500 lines of code here.
So, below you can see our assignmentexpr and basic arithmetic expression rules and actions:
expr: assignexpr
| expr PLUS expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in addition!" : "Second operand isn\'t a number in addition!";
yyerror(token_node, "Both addition operands must be numbers!");
} else
{
double result = $1->numConst + $3->numConst;
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(add, $1, $3, $$, nextquadlabel(), yylineno);
}
}
| expr MIN expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in subtraction!" : "Second operand isn\'t a number in subtracion!";
yyerror(token_node, "Both suctraction operands must be numbers!");
} else
{
double result = $1->numConst - $3->numConst;
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(sub, $1, $3, $$, nextquadlabel(), yylineno);
}
}
| expr MUL expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in subtraction!" : "Second operand isn\'t a number in subtracion!";
yyerror(token_node, "Both multiplication operands must be numbers!");
} else
{
double result = $1->numConst * $3->numConst;
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(mul, $1, $3, $$, nextquadlabel(), yylineno);
}
}
| expr DIV expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in subtraction!" : "Second operand isn\'t a number in subtracion!";
yyerror(token_node, "Both division operands must be numbers!");
} else
{
if($3->numConst == 0) {
yyerror(token_node, "division by 0!");
} else {
double result = $1->numConst / $3->numConst;
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(div_op, $1, $3, $$, nextquadlabel(), yylineno);
}
}
}
| expr MOD expr
{
bool isExpr1Arithm = check_arith($1);
bool isExpr2Arithm = check_arith($3);
if(!isExpr1Arithm || !isExpr2Arithm)
{
//string msg = !isExpr1Arithm ? "First operand isn\'t a number in subtraction!" : "Second operand isn\'t a number in subtracion!";
yyerror(token_node, "Both modulus operands must be numbers!");
} else
{
if($3->numConst == 0) {
yyerror(token_node, "division by 0!");
} else {
double result = fmod($1->numConst,$3->numConst);
$$ = newexpr(arithmetic_e);
$$->sym = newtemp(scope);
$$->numConst = result;
emit(mod_op, $1, $3, $$, nextquadlabel(), yylineno);
}
}
}
...
assignexpr: lvalue ASSIGN expr { if ( isMemberOfFunc )
{
isMemberOfFunc=false;
}
else{ if ( islocalid==true ){
islocalid = false;
}else{
if ( isLibFunc($1->sym->key) ) yyerror(token_node,"Library function \"" + $1->sym->key + "\" is not lvalue!");
if (SymTable_lookup(symtab,$1->sym->key,scope,false) && isFunc($1->sym->key,scope)) yyerror(token_node,"User function \"" + $1->sym->key + "\" is not lvalue!");
}
}
if($1->type == tableitem_e)
{
// lvalue[index] = expr
emit(tablesetelem,$1->index,$3,$1,nextquadlabel(),yylineno);
$$ = emit_iftableitem($1,nextquadlabel(),yylineno, scope);
$$->type = assignment;
} else
{
emit(assign,$3,NULL,$1,nextquadlabel(),yylineno); //lval = expr;
$$ = newexpr(assignment);
$$->sym = newtemp(scope);
emit(assign, $1,NULL,$$,nextquadlabel(),yylineno);
}
}
;
The printQuads method is the following:
void printQuads() {
unsigned int index = 1;
cout << "quad#\t\topcode\t\tresult\t\targ1\t\targ2\t\tlabel" <<endl;
cout << "-------------------------------------------------------------------------------------------------" << endl;
for(quad q : quads) {
string arg1_type = "";
string arg2_type = "";
cout << "quad before arg1 type check" << endl;
if(q.arg1 != nullptr) {
switch (q.arg1->type) {
case const_bool:
arg1_type = "\'" + BoolToString(q.arg1->boolConst) + "\'";
break;
case const_string:
arg1_type = "\"" + q.arg1->strConst + "\"";
break;
case const_num:
arg1_type = to_string(q.arg1->numConst);
break;
case var:
arg1_type = q.arg1->sym->key;
break;
case nil_e:
arg1_type = "nil";
break;
default:
arg1_type = q.arg1->sym->key;
break;
}
}
cout << "quad before arg2 type check" << endl;
if(q.arg2 != nullptr) {
switch (q.arg2->type) {
case const_bool:
arg2_type = "\'" + BoolToString(q.arg2->boolConst) + "\'";
break;
case const_string:
arg2_type = "\"" + q.arg2->strConst + "\"";
break;
case const_num:
arg2_type = to_string(q.arg2->numConst);
break;
case nil_e:
arg2_type = "nil";
break;
default:
arg2_type = q.arg2->sym->key;
break;
}
}
string label = "";
if(q.op == if_eq || q.op == if_noteq || q.op == if_lesseq || q.op == if_greatereq
|| q.op == if_less || q.op == if_greater || q.op == jump) label = q.label;
string resultKey = "";
cout << "quad before key check" << endl;
if(q.result != nullptr && q.result->sym != nullptr) {
cout << "quad " << opcodeStrings[q.op] << " inside if key check for" << opcodeStrings[q.op] << endl;
resultKey = q.result->sym->key;
}
cout << "quad after key check" << endl;
cout << index << ":\t\t" << opcodeStrings[q.op] << "\t\t" << resultKey << "\t\t" << arg1_type << "\t\t" << arg2_type << "\t\t" << label << "\t\t" << endl;
index++;
}
}
The quads variable is just a vector of quads. Here is the quad struct:
enum expr_t {
var,
tableitem_e,
user_func,
lib_func,
arithmetic_e,
assignment,
newtable_e,
const_num,
const_bool,
const_string,
nil_e,
bool_e
};
struct expr {
expr_t type;
binding* sym;
expr* index;
double numConst;
string strConst;
bool boolConst;
expr* next;
};
struct quad {
iopcode op;
expr* result;
expr* arg1;
expr* arg2;
unsigned int label;
unsigned int line;
};
The binding* is defined as follows and is a symbol table binding:
enum SymbolType{GLOBAL_, LOCAL_, FORMAL_, USERFUNC_, LIBFUNC_, TEMP};
struct binding{
std::string key;
bool isactive = true;
SymbolType sym;
//vector<binding *> formals;
scope_space space;
unsigned int offset;
unsigned int scope;
int line;
};
Here are the emit(), newtemp & newexpr() methods:
void emit(
iopcode op,
expr* arg1,
expr* arg2,
expr* result,
unsigned int label,
unsigned int line
){
quad p;
p.op = op;
p.arg1 = arg1;
p.arg2 = arg2;
p.result = result;
p.label = label;
p.line = line;
currQuad++;
quads.push_back(p);
}
binding *newtemp(unsigned int scope){
string name = newTempName();
binding* sym = SymTable_get(symtab,name,scope);
if (sym== nullptr){
SymTable_put(symtab,name,scope,TEMP,-1);
binding* sym = SymTable_get(symtab,name,scope);
return sym;
}else return sym;
}
string newTempName(){
string temp = "_t" + to_string(countertemp) + " ";
countertemp++;
return temp;
}
expr* newexpr(expr_t exprt){
expr* current = new expr;
current->sym = NULL;
current->index = NULL;
current->numConst = 0;
current->strConst = "";
current->boolConst = false;
current->next = NULL;
current->type = exprt;
return current;
}
unsigned int countertemp = 0;
unsigned int currQuad = 0;
Symbol table cpp file:
#include <algorithm>
bool isHidingBindings = false;
/* Return a hash code for pcKey.*/
static unsigned int SymTable_hash(string pcKey){
size_t ui;
unsigned int uiHash = 0U;
for (ui = 0U; pcKey[ui] != '\0'; ui++)
uiHash = uiHash * HASH_MULTIPLIER + pcKey[ui];
return (uiHash % DEFAULT_SIZE);
}
/*If b contains a binding with key pcKey, returns 1.Otherwise 0.
It is a checked runtime error for oSymTable and pcKey to be NULL.*/
int Bucket_contains(scope_bucket b, string pcKey){
vector<binding> current = b.entries[SymTable_hash(pcKey)]; /*find the entry binding based on the argument pcKey*/
for (int i=0; i<current.size(); i++){
binding cur = current.at(i);
if (cur.key==pcKey) return 1;
}
return 0;
}
/*epistrefei to index gia to bucket pou antistixei sto scope 'scope'.Se periptwsh pou den uparxei
akoma bucket gia to en logw scope, ean to create einai true dhmiourgei to antistoixo bucket sto
oSymTable kai epistrefei to index tou.Diaforetika epistrefei thn timh -1.*/
int indexofscope(SymTable_T &oSymTable, unsigned int scope, bool create){
int index=-1;
for(int i=0; i<oSymTable.buckets.size(); i++) if (oSymTable.buckets[i].scope == scope) index=i;
if ( index==-1 && create ){
scope_bucket newbucket;
newbucket.scope = scope;
oSymTable.buckets.push_back(newbucket);
index = oSymTable.buckets.size()-1;
}
return index;
}
/*If there is no binding with key : pcKey in oSymTable, puts a new binding with
this key and value : pvvValue returning 1.Otherise, it just returns 0.
It is a checked runtime error for oSymTable and pcKey to be NULL.*/
int SymTable_put(SymTable_T &oSymTable, string pcKey,unsigned int scope, SymbolType st, unsigned int line){
int index = indexofscope(oSymTable,scope, true);
if(index==-1) cerr<<"ERROR"<<endl;
scope_bucket *current = &oSymTable.buckets.at(index);
if ( Bucket_contains(*current, pcKey) && st != FORMAL_ && st != LOCAL_) return 0; /*If the binding exists in oSymTable return 0.*/
binding newnode;
newnode.key = pcKey;
newnode.isactive = true;
newnode.line = line;
newnode.sym = st;
newnode.scope = scope;
current->entries[SymTable_hash(pcKey)].push_back(newnode);
return 1;
}
/*Pairnei ws orisma to oSymTable kai to scope pou theloume na apenergopoihsoume.
An to sugkekrimeno scope den uparxei sto oSymTable epistrefei -1.Diaforetika 0*/
void SymTable_hide(SymTable_T &oSymTable, unsigned int scope){
isHidingBindings = true;
for(int i=scope; i >= 0; i--) {
if(i == 0) return;
int index = indexofscope(oSymTable,i,false);
if(index == -1) continue;
scope_bucket *current = &oSymTable.buckets.at(index);
for (int i=0; i<DEFAULT_SIZE; i++) {
for (int j=0; j<current->entries[i].size(); j++) {
if(current->entries[i].at(j).sym == LOCAL_ || current->entries[i].at(j).sym == FORMAL_)
current->entries[i].at(j).isactive = false;
}
}
}
}
void SymTable_show(SymTable_T &oSymTable, unsigned int scope){
isHidingBindings = false;
for(int i=scope; i >= 0; i--) {
if(i == 0) return;
int index = indexofscope(oSymTable,i,false);
if(index == -1) continue;
scope_bucket *current = &oSymTable.buckets.at(index);
for (int i=0; i<DEFAULT_SIZE; i++) {
for (int j=0; j<current->entries[i].size(); j++) {
if(current->entries[i].at(j).sym == LOCAL_ || current->entries[i].at(j).sym == FORMAL_)
current->entries[i].at(j).isactive = true;
}
}
}
}
bool SymTable_lookup(SymTable_T oSymTable, string pcKey, unsigned int scope, bool searchInScopeOnly){
for(int i=scope; i >= 0; i--) {
if(searchInScopeOnly && i != scope) break;
int index = indexofscope(oSymTable,i,false);
if(index == -1) continue;
scope_bucket current = oSymTable.buckets[index];
for(vector<binding> entry : current.entries) {
for(binding b : entry) {
if(b.key == pcKey && b.isactive) return true;
else if(b.key == pcKey && !b.isactive) return false;
}
}
}
return false;
}
binding* SymTable_lookupAndGet(SymTable_T &oSymTable, string pcKey, unsigned int scope) noexcept{
for ( int i=scope; i >= 0; --i ){
int index = indexofscope(oSymTable,i,false );
if (index==-1) continue;
scope_bucket ¤t = oSymTable.buckets[index];
for (auto &entry : current.entries) {
for (auto &b : entry ){
if ( b.key == pcKey ) return &b;
}
}
}
return nullptr;
}
/*Lamvanei ws orisma to oSymTable, kleidh tou tou desmou pou psaxnoume kai to scope tou desmou.
H sunarthsh telika epistrefei to value tou tou desmou.Diaforetika epistrefei 0*/
binding* SymTable_get(SymTable_T &oSymTable, const string pcKey, unsigned int scope){
for ( int i=scope; i >= 0; --i )
{
const int index = indexofscope( oSymTable, i, false );
if ( index == -1 )
{
continue;
}
scope_bucket& current = oSymTable.buckets[index];
for ( auto& entry : current.entries)
{
for ( auto& b : entry )
{
if ( b.key == pcKey )
{
return &b;
}
}
}
}
return nullptr;
}
When run with the following test file, the issue occurs at the z5 = 4 / 2; expression's assign quad:
// simple arithmetic operations
z1 = 1 + 2;
z10 = 1 + 1;
z2 = 1 - 3;
z3 = 4 * 4;
z4 = 5 / 2;
What's confusing is that if I print out the sym->key after each emit() in the arithmetic-related actions, I can see the keys just fine. But once I try to access them inside the printQuads it will fail (for the div operation at least so far). This has me thinking that maybe we are shallow copying the binding* sym thus losing the key? But how come the rest of them are printed normally?
I'm thinking that the issue (which has occured again in the past at various stages) could be caused by us using a ton of copy-by-value instead of by-reference but I can't exactly confirm this because most of the time it works (I'm guessing that means that this is undefined behavior?).
I'm sure this is very difficult to help debug but maybe someone will eyeball something that I can't see after this many hours.
Debugging by eyeballing your code is probably a useful skill, but it's far from the most productive form of debugging. These days, it's much less necessary, since there are lots of good tools which you can use to detect problems. (Here, I do mean "you", specifically. I can't use any of those tools because I don't have your complete project in front of me. And nor do I particularly want it; this is not a request for you to paste hundreds of lines of code).
You're almost certainly right that your problem is related to some kind of undefined behaviour. If you're correct about the bad_alloc exception being thrown by what is effectively a copy of a std::string, then it's most likely the result of the thing being copied from not being a valid std::string. Perhaps it's an actual std::string object whose internal members have been corrupted; perhaps the pointer is not actually pointing to an active std::string (which I think is the real problem, see below). Or perhaps it's something else.
Either way, the error occurred long before the bug manifests itself, so you're only going to stumble upon where it happened by blind luck. On the other hand, there are a variety of memory error detection tools available which may be able to pinpoint the precise moment in which you violated the contract by reading or writing to memory which didn't belong to you. These include Valgrind and AddressSanitizer (also known as ASan); one or both of these is certainly available for the platform on which you are developing your project. (I say that confidently even without knowing what that platform is, but you'll have to do a little research to find the one which works best for your particular environment. Both of those names can be looked up on Wikipedia.) These tools are very easy to use, and extraordinarily useful; they can save you hours or days of debugging and a lot of frustration. As an extra added bonus, they can detect bugs you don't even know you have, saving you the embarrassment of shipping a program which will blow up in the hands of the customer or the person who is marking your assignment. So I strongly recommend learning how to use them.
I probably should leave it at that, because it's better motivation to learn to use the tools. Still, I can't resist making a guess about where the problem lies. But honestly, you will learn a lot more by ignoring what I'm about to say and trying to figure out the problem yourself.
Anyway, you don't include much in the way of information about your SymTable_T class, and the inconsistent naming convention makes me wonder if you even wrote its code; perhaps it was part of the skeleton code you were given for this assignment. From what I can see in SymTable_put and SymTable_get, the SymTable_T includes something like a hash table, but doesn't use the C++ standard library associative containers. (That's a mistake from the beginning, IMHO. This assignment is about learning how to generate code, not how to write a good hash table. The C++ standard library associative containers are certainly adequate for your purposes, whether or not they are the absolute ideal for your use case, and they have the enormous advantages of already being thoroughly documented and debugged.)
It's possible that SymTable_T was not originally written in C++ at all. The use of free-standing functions like SymTable_put and SymTable_get rather than class methods is difficult to explain unless the functions were originally written in C, which doesn't allow object methods. On the other hand, they appear to use C++ standard library collections, as evidenced by the call to push_back in SymTable_put:
current->entries[SymTable_hash(pcKey)].push_back(newnode);
That suggests that entries is a std::vector (although there are other possibilities), and if it is, it should raise a red flag when you combine it with this, from SymTable_get (whitespace-edited to save screen space here):
for ( auto& entry : current.entries) {
for ( auto& b : entry ) {
if ( b.key == pcKey )
return &b;
}
}
To be honest, I don't understand that double loop. To start with, you seem to be ignoring the fact that there is a hash table somewhere in that data structure, but beyond that, it seems to me that entry should be a binding (that's what SymTable_put pushes onto the entries container), and I don't see where a binding is an iterable object. Perhaps I'm not reading that correctly.)
Regardless, evidently SymTable_get is returning a reference to something which is stored in a container, probably a std::vector, and that container is modified from time to time by having new elements pushed onto it. And pushing a new element onto the end of a std::vector invalidates all existing references to every element of the vector. (See https://en.cppreference.com/w/cpp/container/vector/push_back)
Thus, newtemp, which returns a binding* acquired from SymTable_get, is returning a pointer which may be invalidated in the future by some call to SymTable_put (though not by every call to that function; only the ones where the stars unline unhappily). That pointer is then stored into a data object which will (much later) be given to printQuads, which will attempt to use the pointer to make a copy of a string which it will attempt to print. And, as I mentioned towards the beginning of this treatise, trying to use an object which is pointed to by a dangling pointer is Undefined Behaviour.
As a minor note, making a copy of a string in order to print it out is completely unnecessary. A reference would work just fine, and save a bunch of unnecessary memory allocations. But that won't fix the problem (if my guess turns out to be correct) because printing through a dangling pointer is just as Undefined Behaviour as making a copy through a dangling pointer, and will likely manifest in some other mysterious way.
I'm new to C++ and I'm trying to return a struct from a vector of structs by using 2 search criteria.
The function find_city is returning me everything from the defined range, regardless of whether it exists inside the vector of struct.
Here's my code:
struct cityLoc
{
int hRange;
int vRange;
int cityCode;
string cityName;
};
vector<cityLoc> cl1;
// the vector has already been preloaded with data
// function to return my struct from the vector
cityLoc find_city(int hRange, int vRange)
{
for (size_t i = 0; i < cl1.size(); i++)
{
if ((cl1[i].hRange = hRange) && (cl1[i].vRange = vRange))
{
return cl1[i];
}
}
}
int main()
{
for (int i = 0; i < 8; i++)
{
for (int j = 0; j <= 8; j++)
{
cityLoc this_city;
this_city = find_city(i, j);
cout << this_city.hRange << ", " << this_city.vRange << endl;
}
}
return 0;
}
Also, aside from this question, I was previously looking into std::find_if and didn't understand it. If I have the following code, what is the output? How do I modify it such that it returns a struct?
auto it = find_if(cl1.begin(), cl1.end(), [](cityLoc& cl) { return cl.hRange == 1; } );
You have a bug here:
if ((cl1[i].hRange = hRange) && (cl1[i].vRange = vRange))
Those = are assignments, not comparisons! Please enable compiler warnings and you won't be hurt by such obvious typos in future.
std::find_if will return the iterator to the found struct entry if it is successful, std::vector::end() otherwise. So, you should first validate the returning iterator if it is valid or not.
For example:
auto it = std::find_if( cl1.begin(), cl1.end(),
[](const cityLoc& cl) { return cl.hRange == 1; } );
if ( it == cl1.end() )
{
// ERROR: Not found! Return error code etc.
return -1;
}
// And, if found, process it here...
std::cout << it->hRange << '\n';
std::cout << it->vRange << '\n';
The criteria (predicate) part in std::find_if is a lambda expression.
I have a function that looks something like this in pseudocode:
std::string option = "option1" // one of n options, user supplied
for (int i = 0; i < 100000; i++) {
if (option == "option1") {
doFunction1a();
} else if (option == "option2") {
doFunction2a();
} else if (option == "option3") {
doFunction3a();
}
// more code...
if (option == "option1") {
doFunction1b();
} else if (option == "option2") {
doFunction2b();
} else if (option == "option3") {
doFunction3b();
}
}
However, I could avoid the repeated if statement inside the loop by doing something like this:
std::string option = "option1" // one of n options, user supplied
int (*doFunctiona)(int, int);
int (*doFunctionb)(int, int);
if (option == "option1") {
doFunctiona = doFunction1a;
doFunctionb = doFunction1b;
} else if (option == "option2") {
doFunctiona = doFunction2a;
doFunctionb = doFunction2b;
} else if (option == "option3") {
doFunctiona = doFunction3a;
doFunctionb = doFunction3b;
}
for (int i = 0; i < 100000; i++) {
doFunctiona();
// more code...
doFunctionb();
}
I realize that this will have little effect on performance (the time spend by the functions dominates the time it takes to execute the if statement).
However, In terms of "good coding practices", is this a good way to set up variable function calling? With "good" I mean: (1) easily expandable, there could easily be 20 options in the future; 2) results in readable code. I'm hoping there exists some kind of standard method for accomplishing this. If not, feel free to close as opinion based.
Just use an unordered_map and spare yourself the if-else-if-orgy:
std::unordered_map<std::string, std::vector<int (*)(int, int)>> functions;
functions.insert({ "option1", { doFunction1a, doFunction1b } });
...
const auto& vec = functions["option1"];
for(auto& f : vec) f(1, 2);
Beside using map I recommend to use std::function and lambdas which will give you more flexibility and syntax is more friendly (at least for me):
std::unordered_map<std::string, std::function<void()>> functions {
{
"option1",
[] {
functionA();
functionB();
}
},
{
"option2",
[] {
functionC();
functionD();
}
}
};
auto optionFuncIt = functions.find("option1");
if (optionFuncIt != functions.end()) {
optionFuncIt->second();
} else {
std::cerr << "Invalid option name" << std::endl;
}
There is a initial game difficulty which is
game_difficulty=5 //Initial
Every 3 times if you get it right, your difficulty goes up to infinity but every 3 times you get it wrong, your difficulty goes down but not below 5. So, in this code for ex:
if(user_words==words) win_count+=1;
else() incorrect_count+=1;
if(win_count%3==0) /*increase diff*/;
if(incorrect_count%3==0) /*decrease difficulty*/;
How should I go about doing this?
Simple answer:
if(incorrect_count%3==0) difficulty = max(difficulty-1, 5);
But personally I would wrap it up in a small class then you can contain all the logic and expand it as you go along, something such as:
class Difficulty
{
public:
Difficulty() {};
void AddWin()
{
m_IncorrectCount = 0; // reset because we got one right?
if (++m_WinCount % 3)
{
m_WinCount = 0;
++m_CurrentDifficulty;
}
}
void AddIncorrect()
{
m_WinCount = 0; // reset because we got one wrong?
if (++m_IncorrectCount >= 3 && m_CurrentDifficulty > 5)
{
m_IncorrectCount = 0;
--m_CurrentDifficulty;
}
}
int GetDifficulty()
{
return m_CurrentDifficulty;
}
private:
int m_CurrentDifficulty = 5;
int m_WinCount = 0;
int m_IncorrectCount = 0;
};
You could just add this as a condition:
if (user words==words) {
win_count += 1;
if (win_count %3 == 0) {
++diff;
}
} else {
incorrect_count += 1;
if (incorrect_count % 3 == 0 && diff > 5) {
--diff
}
}
For example:
if(win_count%3==0) difficulty++;
if(incorrect_count%3==0 && difficulty > 5) difficulty--;
This can be turned into a motivating example for custom data types.
Create a class which wraps the difficulty int as a private member variable, and in the public member functions make sure that the so-called contract is met. You will end up with a value which is always guaranteed to meet your specifications. Here is an example:
class Difficulty
{
public:
// initial values for a new Difficulty object:
Difficulty() :
right_answer_count(0),
wrong_answer_count(0),
value(5)
{}
// called when a right answer should be taken into account:
void GotItRight()
{
++right_answer_count;
if (right_answer_count == 3)
{
right_answer_count = 0;
++value;
}
}
// called when a wrong answer should be taken into account:
void GotItWrong()
{
++wrong_answer_count;
if (wrong_answer_count == 3)
{
wrong_answer_count = 0;
--value;
if (value < 5)
{
value = 5;
}
}
}
// returns the value itself
int Value() const
{
return value;
}
private:
int right_answer_count;
int wrong_answer_count;
int value;
};
And here is how you would use the class:
Difficulty game_difficulty;
// six right answers:
for (int count = 0; count < 6; ++count)
{
game_difficulty.GotItRight();
}
// check wrapped value:
std::cout << game_difficulty.Value() << "\n";
// three wrong answers:
for (int count = 0; count < 3; ++count)
{
game_difficulty.GotItWrong();
}
// check wrapped value:
std::cout << game_difficulty.Value() << "\n";
// one hundred wrong answers:
for (int count = 0; count < 100; ++count)
{
game_difficulty.GotItWrong();
}
// check wrapped value:
std::cout << game_difficulty.Value() << "\n";
Output:
7
6
5
Once you have a firm grasp on how such types are created and used, you can start to look into operator overloading so that the type can be used more like a real int, i.e. with +, - and so on.
How should I go about doing this?
You have marked this question as C++. IMHO the c++ way is to create a class encapsulating all your issues.
Perhaps something like:
class GameDifficulty
{
public:
GameDifficulty () :
game_difficulty (5), win_count(0), incorrect_count(0)
{}
~GameDifficulty () {}
void update(const T& words)
{
if(user words==words) win_count+=1;
else incorrect_count+=1;
// modify game_difficulty as you desire
if(win_count%3 == 0)
game_difficulty += 1 ; // increase diff no upper limit
if((incorrect_count%3 == 0) && (game_difficulty > 5))
game_difficulty -= 1; //decrease diff;
}
inline int gameDifficulty() { return (game_difficulty); }
// and any other access per needs of your game
private:
int game_difficulty;
int win_count;
int incorrect_count;
}
// note - not compiled or tested
usage would be:
// instantiate
GameDiffculty gameDifficulty;
// ...
// use update()
gameDifficulty.update(word);
// ...
// use access
gameDifficulty.gameDifficulty();
Advantage: encapsulation
This code is in one place, not polluting elsewhere in your code.
You can change these policies in this one place, with no impact to the rest of your code.
I am writing two functions in a program to check if a string has an assigned numeric code to its structure array or if the given numeric code has an assigned string in the same structure array. Basically, if I only know one of the two, I can get the other. I wrote the following:
int PrimaryIndex::check_title_pos(std::string title) {
bool findPos = true;
if (findPos) {
for (int s = 1; s <= 25; s++) {
if (my_list[s].title == title) {
return s;
}
}
} else {
return -1;
}
}
std::string PrimaryIndex::check_title_at_pos(int pos) {
bool findTitle = true;
if (findTitle) {
for (int p = 1; p <= 25; p++) {
if (my_list[p].tag == pos) {
return my_list[p].title;
}
}
} else {
return "No title retrievable from " + pos;
}
}
However, it says not all control paths have a return value. I thought the else {} statement would handle that but it's not. Likewise, I added default "return -1;" and "return "";" to the appropriate functions handling int and string, respectively. That just caused it to error out.
Any idea on how I can keep this code, as I'd like to think it works but cant test it, while giving my compiler happiness? I realize through other searches that it sees conditions that could otherwise end in no returning values but theoretically, if I am right, it should work fine. :|
Thanks
In the below snippet, if s iterates to 26 without the inner if ever evaluating to true then a return statement is never reached.
if (findPos) {
for (int s = 1; s <= 25; s++) {
if (my_list[s].title == title) {
return s;
}
}
}