CODEWITHSUNDEEP
c++syntaxboolean
Tyler Pfaff
Tyler Pfaff

Reputation: 5032

How do I express that I want to do something "if a function returns true/false"

I am making a dictionary program. Before adding a word to the dictionary, the AddWord function calls the SearchForWord function, if the search functions discovers that the word passed to it is already in the dictionary it returns true.

In the add function I want it to move on to the part where it actually adds the word only if the search function returns false (meaning it did not find the word) and I can't figure out how to express this correctly.

Edit: I copied and pasted this all from emacs and the formatting is funky, don't hate.

bool Dictionary:: AddAWord(string word)
{
  ofstream fout;  
  string fileName="#.txt";  
  fileName[0]=toupper(word[0]);  

  if(SearchForWord(word)=false){   //here i figured the SearchForWord function would be called and return either true or false  
    //add word  
  }else{  
    //dont add word  
  }

Here's the full search function if it helps

bool Dictionary::SearchForWord(string word)  
{  
   ofstream fout;  
   ifstream fin;  
   string x;  
   string fileName="#.txt";  
   fileName[0]=toupper(word[0]);  
   fout.open(fileName.data());  
   if(!fin.eof()){  
     while(fin>>x){  
      if(x=word){  
       cout<<"Word found during search";  
       return(Dictionary::success);  
      }  
     }  
    }else{  
       return(Dictionary::failure);  
    }  
}

Upvotes: 1

Views: 10970

Answers (5)

Bill Forster
Bill Forster

Reputation: 6297

You want;

if(SearchForWord(word) == false)

not

if(SearchForWord(word) = false)

As a point of style it would be better to go;

if( !SearchForWord(word) )

Or maybe even better;

bool word_found = SearchForWord(word);
if( !word_found )

I find it really useful to introduce well named boolean variables like that, it enhances readability because reading the conditional out loud in your head now results in "if not word found". Additionally it becomes easier and less confusing to trace progress within most debuggers.

Upvotes: 5

Can&#39;t Tell
Can&#39;t Tell

Reputation: 13426

= is the assignment operator. It is used to assign a value to a variable(like a=5).To check if a is equal to b you have to write a==b. So 

if(SearchForWord(word)=false)

should be changed to 

if(SearchForWord(word)==false)

Upvotes: 0

Justin Thomas
Justin Thomas

Reputation: 5848

You want to do: if(!SearchForWord(word))

Using = is assignment not boolean.

Upvotes: 0

Sherm Pendley
Sherm Pendley

Reputation: 13612

if (!SearchForWord(word)) {
    // add the word
} else {
    // don't add the word
}

Upvotes: 1

corsiKa
corsiKa

Reputation: 82579

You want:

if(!SearchForWord(word))

Never use == when comparing boolean values. You may accidentally assign the value like you are there. Consider this:

if(engagedInNuclearWar = true) { // typo. should be ==
    fireMissiles();
}

Now, when this fires, the first thing it will do, because there's only ONE equals sign, is assign engagedInNuclearWar to be true. This is a mistake, we want to be checking not assigning. As a result, we're firing missiles when we shouldn't. Some intern will probably lose his job over that (if he doesn't get killed in the nuclear holocaust that follows.)

Instead, avoid using == but rely on boolean evaluation.

if(engagedInNuclearWar) { // no chance for = vs == typo
    fireMissiles();
}

Upvotes: 2

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