No.2705
Hey /g/, I'm learning c++ from a book, and to make sure I knew what I've learned so far well enough to move on, I've tried writing a simple program that calculates the amount of time it would take to sing the "bottles of beer on the wall" song, in the users time measurement unit of choice.
However, I've run into a problem that I can't seem to find a solution for. Whenever I run the code, no matter what I put in for the time unit, it measures in seconds. I'll post it below.
My compiler isn't giving me any errors.
____________________________
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No.2706
#include <iostream>
#include <string>
int main()
{
long unsigned int numberOfBottles;
long unsigned int timeLength;
float singingTime = 8.5;
std::string timeUnit = "blank";
std::cout << "What would you like to measure time in?";
std::cout << std::endl;
std::cin >> timeUnit;
if(timeUnit == "Seconds" || "seconds" || "Seconds." || "seconds." || "SECONDS" || "SECONDS.")
{
std::cout << "How many bottles of beer are on the wall?";
std::cout << std::endl;
std::cin >> numberOfBottles;
std::cout << "It would take " << (numberOfBottles*singingTime) << " seconds to sing the song.";
}
else if(timeUnit == "Minutes" || "minutes" || "Minutes." || "minutes." || "MINUTES" || "MINUTES.")
{
std::cout << "How many bottles of beer are on the wall?";
std::cout << std::endl;
std::cin >> numberOfBottles;
std::cout << "It would take " << ((numberOfBottles*singingTime)/60) << " minutes to sing the song.";
}
else
{
std::cout << "Wat.";
}
std::cout << std::endl;
std::cout << "Type 'Exit' to exit.";
std::cout << std::endl;
char response;
std::cin >> response;
return 0;
}
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No.2707
Shit, I don't know why I have an int called "timeLength" in there.
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No.2710
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No.2728
>>2706
your ifs are wrong.
instead of 'timeUnit == "Minutes" || "minutes...' do 'timeUnit == "Minutes" || timeUnit == "minutes"...'.
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No.2729
>>2710
>>2728
Oh man, I had no clue. Now I know. Thanks guys
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No.3033
>>2729
Bear in mind that in C/C++ any non-0 value will evaluate to true...so your or'd string literals effectively become:
if(timeUnit == "Seconds" || true || true || true || true || true)
More importantly, comparing string variations like this is an exercise in insanity - there are too many combinations to effectively parse (what if a grill finds your program and enters "SeCoNdS"?).
Consider normalizing your input string to all lowercase and strip punctuation/trim whitespace:
#include <algorithm>
#include <string>
#include <cctype>
// this is the fancypants way of doing it
std::string data = "Abc";
std::transform(data.begin(), data.end(), data.begin(), ::tolower);
// other processing is left as an exercise to the reader
if(data == "abc")
{
// do stuff
}
You could also match using regular expressions, though I haven't really used regexes in C++ (more in scripting Python or JS):
// you'll need C++11 for this
// if using gcc, add the "-std=c++11" switch
#include <iostream>
#include <regex>
#include <string>
int main()
{
std::cout << "oh herro" << std::endl;
std::string str = "pUmPkIn SpIcE lAtTeE SECONds omg ponies";
// Pattern to match against,
// with case insensitive flag
std::regex expr(".*(second|secs).*",
std::regex_constants::icase);
if(std::regex_match(str, expr))
std::cout << "Yes" << std::endl;
return 0;
}
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No.3277
if you simply used the namespace standard, there would be no need for the incessant std::
>using namespace std;
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No.3310
>>2706
Heh took me 2 seconds
>if(timeUnit == "Seconds" || "seconds" || "Seconds." || "seconds." || "SECONDS" || "SECONDS.")
Pass in seconds
>std::cout << "It would take " << (numberOfBottles*singingTime) << " seconds to sing the song.";
output as seconds...check
> else if(timeUnit == "Minutes" || "minutes" || "Minutes." || "minutes." || "MINUTES" || "MINUTES.")
pass in minutes
>std::cout << "It would take " << ((numberOfBottles*singingTime)/60) << " minutes to sing the song.";
Output is minutes/60 which we on earth call seconds, but you call it minutes....fail
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No.3321
>>2706
i cant remember the exact way to lowercase strings in C++ but this is a better way to make things case insensitive (and is used by most programmers)
if (timeUnit.toLower() == "seconds." || timeUnit.toLower() == "seconds"){doSomeCode();}
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No.3322
>>3321
better yet//when in doubt, paran group
if ((timeUnit.toLower() == "seconds.") || (timeUnit.toLower() == "seconds")){doSomeCode();}
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No.7212
>>2706
To expand on >>2710, it doesn't look at the characters in the string. A string literal is just a char*, and this is what the if statement looks at. Because the pointer isn't nullptr, it evaluates to true. So it would still evaluate to true even with an empty string.
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No.7213
>>7212
Interestingly,
if (*"") cout << "yes" << endl;
...doesn't print anything because it '*""' points to the first character of the string, which is a null terminator (0.) String literals in C/C++ always end in a null terminator. If the string was anything but empty, you'd get true. You're better off using .empty() on C++ string variables though.
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No.7218
>>3321
if it's in a std::string then you can do
std::transform(timeUnit.begin(), timeUnit.end(), timeUnit.begin(), ::tolower);
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No.7223
>>3310
minutes / 60 are hours
seconds / 60 are minutes
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No.7293
>>2706
>if(timeUnit == "Seconds" || "seconds" || "Seconds." || "seconds." || "SECONDS" || "SECONDS.")
>else if(timeUnit == "Minutes" || "minutes" || "Minutes." || "minutes." || "MINUTES" || "MINUTES.")
just convert it to lowercase before testing it.
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