Why does string find not display the intended output

Question

I want to print an error message if the user's input string does not match what is intended. However, std::string::npos does not print it.

void AdvisorBot::printHelpCMD() {
    std::string prod ("prod");
    std::string min ("min");
    std::string max ("max");

    std::string checkInput("prod min max");


    std::cout << "\nEnter the command you need help with e.g <prod>: "  << std::endl;
    std::string cmd;
    std::getline(std::cin, cmd); //takes input and store into string cmd

    if (cmd == prod) {
        std::cout << "\nThis command lists all the available products on the exchange.\n" << std::endl;
    }    

    if (cmd.find(checkInput) != std::string::npos) { //to loop over inputted strings and check if matches above NOT WORKING
        std::cout << "\nCommand does not exist\n" << std::endl;
    }

@tkausl when its ==, the string "Commad does not exist" is printed even when the user input is correct. For example, if user types prod, the error appears — LearningToCode
– LearningToCode, Commented Dec 25, 2022 at 6:38
The logic in the if is backwards. If the returned value equals std::string::npos then there was no match. — Retired Ninja
– Retired Ninja, Commented Dec 25, 2022 at 6:38
The error won't appear if you input the search term, i.e. prod min max. — tkausl
– tkausl, Commented Dec 25, 2022 at 6:40

Alan Birtles · Accepted Answer · 2022-12-25 06:57:54Z

1

cmd.find(checkInput) looks for the whole string checkInput in cmd which is presumably not what you want.

If you want to check whether your string is one of a list of values std::set might work better:

#include <set>

...

std::set<std::string> checkInput { "prod", "min", "max" };
if (checkInput.find(cmd) == checkInput.end()) {
    std::cout << "\nCommand does not exist\n" << std::endl;
}

edited Dec 25, 2022 at 6:57

answered Dec 25, 2022 at 6:52

Alan Birtles

38.3k4 gold badges39 silver badges73 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Why does string find not display the intended output

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related