I'm trying to declare an unordered map into my program in which I will map them to tokens in another file.
I need a method which returns the Token type found in Token.h (which is an enum class)
What is confusing me is that, since I want to return the mapped Tokens from the unordered_map to the enum class, what should be the return type of the method? Also, it is stating that
error: 'unordered_map' does not name a type
I am rather new to C++ and am still finding it a bit hard in this case how I should declare methods. I've read that the unordered map should be declared INSIDE a method, but since I want the value returned by the map, which should be the return type?
I tried this
Test 1
Token Lexer::getTokenType()
{
unordered_map<string,Token> tokenType;
}
This outputs these errors:
Test 2 I tried this
#include <iostream>
#include <fstream>
#include <string>
#include <stdlib.h>
#include <stdio.h>
#include <sstream>
#include <wctype.h>
#include <map>
#include "lexer.h"
using namespace std;
long Row, Col, Offset;
unordered_map<string, Token> ProtectedWords
{
}
OR
unordered_map<string, Token>::Lexer::getTokenType()
{
}
still yielded the same
Its error:
I know these do sound stupid, but would you mind explain to me please? As in the tutorial I followed many are, yes, called inside a method, but even that did not work
You need to include <unordered_map>.
You'll also need to enable C++11 support, if you haven't already done so: for GCC, make sure the compiler arguments include -std=c++11 (or c++0x if you're using an old compiler).
Related
So I was trying to access a method that is defined in another class and has the prototype in the header. I'm pretty positive I defined it but it keeps popping up undefined reference to SafeCracker.
Main.cpp
#include <iostream>
#include "mystuff.h"
using namespace std;
void BigDog(int KibblesCount);
int main()
{
cout << SafeCracker(1);
return 0;
}
mystuff.cpp
#include <iostream>
using namespace std;
string SafeCracker(int SafeID)
{
return "123456";
}
mystuff.h
using namespace std;
#ifndef MYSTUFF_H_INCLUDED
#define MYSTUFF_H_INCLUDED
string SafeCracker(int SafeID);
#endif // MYSTUFF_H_INCLUDED
Here it tells you that you have an undefined reference, so you don't really have a problem with the prototype.
Had you forgotten to include the header file that contains the prototype you would have gotten something like
main.cpp: In function ‘int main()’:
main.cpp:8:13: error: ‘SafeCracker’ was not declared in this scope
cout << SafeCracker(1);
Your undefined reference is a linker error. The most likely cause would be that you did not use mystuff.cpp when compiling
If you're compiling from the command line, you should give both files as parameters.
If you're using an IDE that calls the compiler, make sure that the file is part of the project.
For example in Code::Blocks right-click on the file name and go "add to project" (If I remember correctly)
It is also possible that you made a typo in the function declaration in mystuff.cpp (that doesn't seem to be the case here though)
Now there is one important thing about your code you should take note of:
It is very bad practice to put a using namespace in a header file.
using namespace std; in a .cpp source file is mostly up to you, and that using statement will only apply to that particular file.
But if you put it in a header file that is meant to be included through #include , the using there will be forced upon any code that includes it.
Here is an example:
main.cpp
#include <iostream>
// including mystuff.h to use that awesome SafeCracker()
#include "mystuff.h"
// I need to use an std::map (basically an associative array)
#include <map>
// the map of my game
class map
{
int tiles[10][10];
};
int main()
{
// The std map I need to use
std::map<int, int> mymappedcontainer;
// The map of my game I need to use
map mytiles;
// The reason why I need to include mystuff.h
cout << SafeCracker(1);
return 0;
}
Normally, my class map should not be a problem since the map I included from the standard library is inside the namespace std, so to use it you would need to go std::map.
The problem here is that, since mystuff.h has using namespace std; in it, the symbol map is already used, and that creates a conflict.
You do not now who will use your header files, or if you will use them again a long time from now, and maybe then you will want to use name that is already used in the std namespace.
I advise you to use std:: before things taken from the standard libraries instead (std::string instead of just string for example)
PS: In C++, "class" refers to a class data structure, and the functions you made here are not part of any class. You should say "defined in another file" or "defined in another translation unit" instead
I am new to c++, and I am trying to get a basic program to initialize a list of short unsigned integers. I am compiling and running using scygwin and g++.
Below is the code in the .cpp file:
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <typeinfo>
using namespace std;
int main (int argc, char* argv[]) {
list<int> events;
return 0;
}
which I run by typing the following command into cygwin terminal:
$ g++ -o test.out test.cpp
However, I get the following compilation errors:
test.cpp: In function ‘int main(int, char**)’: test.cpp:16:1: error:
‘list’ was not declared in this scope list events;
^
test.cpp:16:6: error: expected primary-expression before ‘int’
list events;
^
I am confused about why list is not in the scope, since I am using namespace std? I found a similar question asked about this on a c++ forum, but my problem would be resolved with that. Anyone know what the problem is here?
-Paul
using namespace std; doesn't add any functionality to your code. It just means you don't have to type std:: when referencing things in the std namespace, like std::list.
To actually include the code base for std::list into your program, you need to add:
#include <list>
When in doubt about this kind of thing, doing a google search for cpp reference list will turn up a page like this where you can see: Defined in header <list> at the top.
Here's another question about using namespace std; that may prove useful and why you shouldn't use it. I'll add a little bit to perhaps explain namespaces.
It is common in C++ programs to organize functions into classes and namespaces. Imagine you wrote your own list class to handle certain scenarios. In order to prevent naming conflicts you would put it in a different namespace than std.
namespace MyApp {
class list;
void sort(list&);
}
For the majority of a large code base you might still prefer to use std::list but you need MyApp::list for some things. Using namespaces you can cluster your code and prevent naming conflicts for similar functionality.
Summary
using namespace std; makes it so that if you reference a function or class not in the global namespace it looks for it in the std namespace.
#include <list> actually inserts prototypes (information about how to access the code) in your source file during the preprocessor stage.
I am doing everything correctly as far as I can tell and I have gotten the error message:
error: 'unordered_map' does not name a type
error: 'mymap' does not name a type
In my code, I have:
#include <unordered_map>
using namespace std;
//global variable
unordered_map<string,int> mymap;
mymap.reserve(7000);
void main {
return;
}
I don't see what can be missing here....
EDIT: when I update my declaration to
std::tr1::unordered_map<string,int> mymap;
I an able to eliminate the first error, but when I try to reserve, I still get the second error message.
EDIT2: As pointed out below, reserve must go into main and I need to compile with flag
-std=c++0x
However, there still appear to be errors related to unordered_map, namely:
error: 'class std::tr1::unordered_map<std::basic_string<char>, int>' has no member named 'reserve'
Compile with g++ -std=c++11 (my gcc version is gcc 4.7.2) AND
#include <unordered_map>
#include <string>
using namespace std;
//global variable
unordered_map<string,int> mymap;
int main() {
mymap.reserve(7000); // <-- try putting it here
return 0;
}
If you want to support <unordered_map> for versions older than c++11 use
#include<tr1/unordered_map> and declare your maps in the form :- std::tr1::unordered_map<type1, type2> mymap
which will use the technical report 1 extension for backward compatibility.
You can't execute arbitrary expressions at global scope, so you should put
mymap.reserve(7000);
inside main.
This is also true for other STL containers like map and vector.
After fixing the previous problem (see my one other question that I have asked). I had declared more classes.
One of these is called CombatAdmin which does various things: (Header file)
#ifndef COMBATADMIN_H
#define COMBATADMIN_H
#include <string> // Need this line or it complains
#include <Player.h>
#include <Sound.h>
#include <Enemy.h>
#include <Narrator.h>
using namespace std;
class Enemy;
class Player;
class CombatAdmin // Code yet to be commented here, will come soon.
{
public:
CombatAdmin();
void healthSet(double newHealth, string playerName);
void comAdSay(string sayWhat);
void playerFindsChest(Player *player,Weapon *weapon,Armour *armour);
void youStoleOurStuffEncounter(Player *player);
void comAdWarning(string enemyName);
void comAdAtkNote(string attack, double damage,string target,string aggresor);
void entDefeated(string entName);
void comAdStateEntHp(string ent, double hp);
void comAdStateScanResults(string enemyName, double enemyHealth);
string doubleToString(double number);
string intToString(int number);
bool isRandEncounter();
void randomEncounter(Player *player,Sound *sound,Narrator *narrator);
bool combatRound(Player *player, Enemy *enemy, Sound *sound, bool ran);
void playerFindsItem(string playerName,string itemName,double itemWeight,double playerWeight);
void playerFindsGold(string playerName,double coinCnt,double playerCoinCnt);
};
#endif // COMBATADMIN_H
It is then instanced in the main.cpp file like this: (Snippet of the main.cpp file)
#include <iostream> // Required for input and output
#include <Item.h> // Item header file.
#include <Weapon.h> // Header files that I have made for my classes are needed for this program
#include <sstream> // Needed for proper type conversion functions
#include <windows.h> // for PlaySound() and other functions like sleep.
#include <time.h> // Needed to seed the rand() function.
#include <mmsystem.h> // Not sure about this one, possibly defunct in this program.
#include <stdio.h> // Needed for a similar kind of output as iostream for various functions error msgs.
#include <irrKlang.h> // The header file of the sound lib I am using in this program.
#include <Narrator.h> // The narrators's header file.
#include <Pibot.h> // Other header files of classes.
#include <Armour.h>
#include <Player.h>
#include <Weapon.h>
#include <CombatAdmin.h>
using namespace irrklang;
using namespace std;
// Forward referenced functions
void seedRandom(); // Seeds the random number so it will be random as apposed to pseudo random.
string getPlayerName(string temp); // Gets the player's new name.
int main(int argc, char* argv[])
{
// Variables and object pointers declared here.
CombatAdmin *comAd = new CombatAdmin(); // Handles combat.
Narrator *narrator = new Narrator(); // The Narrator that says stuff
Pibot *piebot = new Pibot(); // PIbot, the player's trusty companion
string temp; // Temp string for input and output
However, when I try to compile the project, I get the following error:
C:\Documents and Settings\James Moran.HOME-B288D626D8\My Documents\C++ projects\Test Project\main.cpp|59|undefined reference to `CombatAdmin::CombatAdmin()'|
I am using the Code::Blocks IDE (ver 10.05), with the GNU GCC compiler. The project is of type "Console application". I am using windows XP 32 bit SP3.
I have tried changing to search directories to include where the object files are, but no success there.
As can be seen from the code, the narrator and PIbot are instanced just fine. (then used, not shown)
My question is, therefore, what do I need to do to stop these errors occurring? As when I encountered similar "Undefined reference to x" errors before using libraries. I had just forgotten to link to them in Code::Blocks and as soon as I did, they would work.
As this class is of my own making I am not quite sure about this.
Do say if you need more information regarding the code etc.
You have declared the default constructor (CombatAdmin()) and thus prevented the compiler from automatically generating it. Thus, you either need to 1) remove declaration of the default constructor from the class, or 2) provide an implementation.
I had this kind of error and the cause was that the CombatAdmin.cpp file wasn't selected as a Build target file: Prject->Properties->Build targets
Are you sure you've to include your header as:
#include <CombatAdmin.h>
?
I think you need to include your header file as:
#include "CombatAdmin.h"
And same for other headers written by you, like these:
#include "Armour.h"
#include "Player.h"
#include "Weapon.h"
//and similarly other header files written by you!
See this topic:
What is the difference between #include <filename> and #include "filename"?
My solution was just to add a line in the header before the class defenition:
class CombatAdmin;
I was doing a project for computer course on programming concepts. This project was to be completed in C++ using Object Oriented designs we learned throughout the course. Anyhow, I have two files symboltable.h and symboltable.cpp. I want to use a map as the data structure so I define it in the private section of the header file. I #include <map> in the cpp file before I #include "symboltable.h".
I get several errors from the compiler (MS VS 2008 Pro) when I go to debug/run the program the first of which is:
Error 1 error C2146: syntax error : missing ';' before identifier 'table' c:\users\jsmith\documents\visual studio 2008\projects\project2\project2\symboltable.h 22 Project2
To fix this I had to #include <map> in the header file, which to me seems strange.
Here are the relevant code files:
// symboltable.h
#include <map>
class SymbolTable {
public:
SymbolTable() {}
void insert(string variable, double value);
double lookUp(string variable);
void init(); // Added as part of the spec given in the conference area.
private:
map<string, double> table; // Our container for variables and their values.
};
and
// symboltable.cpp
#include <map>
#include <string>
#include <iostream>
using namespace std;
#include "symboltable.h"
void SymbolTable::insert(string variable, double value) {
table[variable] = value; // Creates a new map entry, if variable name already exist it overwrites last value.
}
double SymbolTable::lookUp(string variable) {
if(table.find(variable) == table.end()) // Search for the variable, find() returns a position, if thats the end then we didnt find it.
throw exception("Error: Uninitialized variable");
else
return table[variable];
}
void SymbolTable::init() {
table.clear(); // Clears the map, removes all elements.
}
My guess is that you have another file that includes the header file #include "symboltable.h". And that other source file doesn't #include <map> nor #include <string> nor has using namespace std before it includes "symboltable.h".
Check which file is being compiled when you get the error. Is it maybe a different source file than the .cpp that you mentioned? Possibly something like main.cpp?
Another way to solve your problem is to put the includes you need in your header file and use std::map instead of simply map. Also you use string which is also inside the namespace std. So that needs to be std::string. And put the missing #include <string>.
Yes, you indeed have to #include <map> in the header file.
You use map in the declaration of the class, so the compiler needs to know what this map refers to. Since the definition of it is in <map> you need to include that header before using the map template class.
You could also instead #include <map> in every source file before the #include "symboltable.h" line, but usually you would just include these kind of prerequisites in the header.