Why does string find not display the intended output - c++

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;
}

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;
}

Related

Problems printing from map<string, struct> in C++

I'm learnig C++. Here is my problem: I'm trying to read data from a text file and save it to a map<string, struct> and then have it print out all the keys from the map preferably in alphabetical order. The data has 2 strigns and a float. I can't get this to print even after having tried many different solutions.
Heres what I've got so far:
Here is my struct:
struct category
{
std::string tram_stop;
float dist;
};
using Tram = std::map<std::string, std::vector<category>>;
Here is where I try to save the data to the map.
void store(Tram& tram, std::vector<std::string>& tram_data)
{
if (tram.find (tram_data.at (0)) == tram.end ())
{
tram[tram_data.at (0)] = {};
}
else
{
tram.at (tram_data.at (0)).push_back (category {tram_data.at (1), std::stof(tram_data.at(2))});
}
}
And here is main().
int main()
{
Tram tram;
print_rasse();
// Ask input filename.
std::string filename;
std::cout << "Give a name for input file: ";
std::cin >> filename;
// Read input file.
std::ifstream file_in;
file_in.open (filename);
if (!file_in.is_open ())
{
std::cout << INVALID_FILE << std::endl;
return EXIT_FAILURE;
}
std::vector<std::string> tram_data;
if (file_in.is_open())
{
std::string line;
while( std::getline(file_in,line) )
{
std::stringstream ss(line);
std::string tram_line, tram_stop, distance;
std::getline(ss,tram_line,';'); //std::cout<< ""<<tram_line <<" ";
std::getline(ss,tram_stop,';'); //std::cout<<" "<<tram_stop<<" ";
std::getline(ss,distance); //std::cout<<" "<<distance<< " ";
if (tram_line != "" && tram_stop != "")
{
tram_data.push_back (tram_line);
tram_data.push_back (tram_stop);
tram_data.push_back (distance);
//std::cout << tram_line << " " << distance << std::endl;
}
else
{
std::cout << INVALID_FORMAT << std::endl;
return EXIT_FAILURE;
}
}
file_in.close ();
store(tram, tram_data);
}
This is the part I think doesn't work. Tried different iterators too.
if (upper_com == "LINES")
{
std::cout << "All tramlines in alphabetical order:" << std::endl;
for (auto& item : tram)
{
std::cout << item.first << std::endl;
}
}
Your implementation of store will create a vector for the first item added for a particular tram_data[0] value, but will not add anything to the vector. This results in losing that first item, and can result in no output because of the empty vectors.
That function can be simplified:
void store(Tram& tram, std::vector<std::string>& tram_data)
{
if (tram_data.size() < 3) throw std::out_of_range();
tram[tram_data[0]].emplace_back(tram_data[1], std::stof(tram_data[2]));
}
You don't need to use at with tram because you want to create the entry if it doesn't exist. at with tram_data will result in an exception being thrown if there are fewer than three elements in tram_data, so that check has been moved outside all the accesses to the vector.

Check user input by each char if exists in char array [duplicate]

I want to write a function that determines if all the letters of an inputted word are contained in another string of acceptable letters.
bool ContainsOnly(std::string inputtedWord, std::string acceptableLetters)
{
// ... how do I write this?
}
Here's my testing framework:
bool Tester(std::string inputtedWord, std::string acceptableLetters)
{
if (ContainsOnly(inputtedWord, acceptableLetters)) {
std::cout << "Good!" << std::endl;
return true;
}
else {
std::cout << "No good!" << std::endl;
return false;
}
}
int main()
{
std::string acceptableLetters;
std::string inputtedWord;
std::cout << "Please input the acceptable letters in your words: " << std::endl;
std::cin >> acceptableLetters;
while (inputtedWord != "STOP")
{
std::cout << "Please input the word you would like to test: (type STOP to end testing): " << std::endl;
std::cin >> inputtedWord;
Tester(inputtedWord, acceptableLetters);
}
return 0;
}
I want the following output:
Please input the acceptable letters in your words: CODING
Please input the word you would like to test: (type STOP to end testing): COIN
Good!
Please input the word you would like to test: (type STOP to end testing): COP
No good!
You can use find_first_not_of like this:
bool ContainsOnly(std::string inputtedWord, std::string acceptableLetters)
{
return inputtedWord.find_first_not_of(acceptableLetters) == std::string::npos;
}
Here's a demo.
Put all the acceptable characters to std::set.
Judge if all characters in the strings are in the set via std::all_of.
#include <set>
#include <algorithm>
bool ContainsOnly(std::string inputtedWord, std::string acceptableLetters)
{
std::set<char> okSet(acceptableLetters.begin(), acceptableLetters.end());
return std::all_of(inputtedWord.begin(), inputtedWord.end(),
[&okSet](char c)
{
return okSet.find(c) != okSet.end();
});
}

What am I doing wrong here with find and string?

I am asking user to enter date in format with slashes. Then I try to find the slashes in the string using find. I get error saying I cannot compare pointer with integer on my if statement. Here is code.
// test inputing string date formats
#include <iostream>
#include <string>
#include <algorithm>
int main() {
std::string dateString;
int month,day,year;
std::cout << "Enter a date in format of 5/14/1999: ";
std::getline(std::cin,dateString);
std::cout << "You entered " << dateString << std::endl;
if (std::find(dateString.begin(),dateString.end(),"/") != dateString.end()) {
std::cout << "Found slash in date.\n";
}
else {
std::cout << "screwed it up.\n";
}
}
Any help is appreciated.
if (std::find(dateString.begin(),dateString.end(),"/") != dateString.end()) {
"/" is a literal string, or a const char * (actually a const char[2] in this case, to be pedantic, but this is not germane) . The third parameter to std::find, in this case, should be a char, a single character.
You probably meant
if (std::find(dateString.begin(),dateString.end(),'/') != dateString.end()) {
I think you can use
if (dateString.find("/") != std::string::npos) {
std::cout << "Found slash in date.\n";
} else {
std::cout << "screwed it up.\n";
}
to find substring/char in a string. Note that std::string::find() works for char, const char * and std::string.

Find an exact substr in a string

I have a text file which contains the following text
License = "123456"
GeneralLicense = "56475655"
I want to search for License as well as for GeneralLicense.
while (getline(FileStream, CurrentReadLine))
{
if (CurrentReadLine.find("License") != std::string::npos)
{
std::cout << "License Line: " << CurrentReadLine;
}
if (CurrentReadLine.find("GeneralLicense") != std::string::npos)
{
std::cout << "General License Line: " << CurrentReadLine;
}
}
Since the word License also present in the word GeneralLicense so if-statement in the line if (CurrentReadLine.find("License") != std::string::npos) becomes true two times.
How can I specify that I want to search for the exact sub-string?
UPDATE: I can reverse the order as mentioned by some Answers OR check if the License is at Index zero. But isn't there anything ROBOUST (flag or something) which we can speficy to look for the exact match (Something like we have in most of the editors e.g. MS Word etc.).
while (getline(FileStream, CurrentReadLine))
{
if (CurrentReadLine.find("GeneralLicense") != std::string::npos)
{
std::cout << "General License Line: " << CurrentReadLine;
}
else if (CurrentReadLine.find("License") != std::string::npos)
{
std::cout << "License Line: " << CurrentReadLine;
}
}
The more ROBUST search is called a regex:
#include <regex>
while (getline(FileStream, CurrentReadLine))
{
if(std::regex_match(CurrentReadLine,
std::regex(".*\\bLicense\\b.*=.*")))
{
std::cout << "License Line: " << CurrentReadLine << std::endl;
}
if(std::regex_match(CurrentReadLine,
std::regex(".*\\bGeneralLicense\\b.*=.*")))
{
std::cout << "General License Line: " << CurrentReadLine << std::endl;
}
}
The \b escape sequences denote word boundaries.
.* means "any sequence of characters, including zero characters"
EDIT: You could also use regex_search instead of regex_match to search for substrings that match instead of using .* to cover the parts that don't match:
#include <regex>
while (getline(FileStream, CurrentReadLine))
{
if(std::regex_search(CurrentReadLine, std::regex("\\bLicense\\b")))
{
std::cout << "License Line: " << CurrentReadLine << std::endl;
}
if(std::regex_search(CurrentReadLine, std::regex("\\bGeneralLicense\\b")))
{
std::cout << "General License Line: " << CurrentReadLine << std::endl;
}
}
This more closely matches your code, but note that it will get tripped up if the keywords are also found after the equals sign. If you want maximum robustness, use regex_match and specify exactly what the whole line should match.
You can check if the position at which the substring appears is at index zero, or that the character preceding the initial position is a space:
bool findAtWordBoundary(const std::string& line, const std::string& search) {
size_t pos = line.find(search);
return (pos != std::string::npos) && (pos== 0 || isspace(line[pos-1]));
}
Isn't there anything ROBUST (flag or something) which we can specify to look for the exact match?
In a way, find already looks for exact match. However, it treats a string as a sequence of meaningless numbers that represent individual characters. That is why std::string class lacks the concept of "full word", which is present in other parts of the library, such as regular expressions.
You could write a function that tests for the largest match first and then returns what ever information you want about the match.
Something a bit like:
// find the largest matching element from the set and return it
std::string find_one_of(std::set<std::string, std::greater<std::string>> const& tests, std::string const& s)
{
for(auto const& test: tests)
if(s.find(test) != std::string::npos)
return test;
return {};
}
int main()
{
std::string text = "abcdef";
auto found = find_one_of({"a", "abc", "ab"}, text);
std::cout << "found: " << found << '\n'; // prints "abc"
}
If all matches start on pos 0 and none is prefix of an other, then the following might work
if (CurrentReadLine.substr( 0, 7 ) == "License")
You can tokenize your string and do a full comparison with your search key and the tokens
Example:
#include <string>
#include <sstream>
#include <vector>
#include <iostream>
auto tokenizer(const std::string& line)
{
std::vector<std::string> results;
std::istringstream ss(line);
std::string s;
while(std::getline(ss, s, ' '))
results.push_back(s);
return results;
}
auto compare(const std::vector<std::string>& tokens, const std::string& key)
{
for (auto&& i : tokens)
if ( i == key )
return true;
return false;
}
int main()
{
std::string x = "License = \"12345\"";
auto token = tokenizer(x);
std::cout << compare(token, "License") << std::endl;
std::cout << compare(token, "GeneralLicense") << std::endl;
}

C++ - Reading Columns of a CSV files and only keeping ones that start with a specific string

so I am trying to figure out how to sort CSV files to help organize data that I need for an economics paper. The files are massive and there are a lot of them (about 587 mb of zipper files). The files are organized by columns in that all the variable names are in the first line and all the data for that variable is all below it. My goal is to be able to only take the columns that start with the an indicated string (ex input: "MC1", Get: MC10RT2,MC1WE02,...) and then save them into a separate file. Does anyone have any advice as to what the form that the code should take?
Just for fun a small program that should work for you. The thing you'll be intersted in is boost::split(columns, str, boost::is_any_of(","), boost::token_compress_off); that here create a vector of string from your csv-style string.
Very basic example, but your question was an excuse to play a bit with boost string algorithms, that I did know but never used...
#include <boost/algorithm/string.hpp>
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <set>
// Typedefs for eye candy
typedef std::vector<std::string> Fields;
typedef std::vector<Fields> Results;
typedef std::set<unsigned long> Columns;
// Split the CSV string to a vector of string
Fields split_to_fields(const std::string& str)
{
Fields columns;
boost::split(columns, str, boost::is_any_of(","),
boost::token_compress_off);
return columns;
}
// Read all the wanted columns
Results read_columns_of_csv(std::istream& stream, const Columns& wanted_columns)
{
std::string str;
Results results;
while (getline(stream, str))
{
Fields line{split_to_fields(str)};
Fields fields;
for (unsigned long wanted_column: wanted_columns)
{
if (line.size() < wanted_column)
{
std::cerr << "Line " << (results.size() + 1 )
<< " does not contain enough fields: "
<< line.size() << " < " << wanted_column
<< std::endl;
}
else
{
fields.push_back(line[wanted_column]);
}
}
results.push_back(fields);
}
return results;
}
// Read the ids of the columns you want to get
Columns read_wanted_columns(unsigned long max_id)
{
Columns wanted_columns;
unsigned long column;
do
{
std::cin >> column;
if ((column < max_id)
&& (column > 0))
{
wanted_columns.insert(column - 1);
}
}
while (column > 0);
return wanted_columns;
}
// Whole read process (header + columns)
Results read_csv(std::istream& stream)
{
std::string str;
if (!getline(stream, str))
{
std::cerr << "Empty file !" << std::endl;
return Results{};
}
// Get the column name
Fields columns{split_to_fields(str)};
// Output the column with id
unsigned long column_id = 1;
std::cout
<< "Select one of the column by entering its id (enter 0 to end): "
<< std::endl;
for (const std::string elem: columns)
{
std::cout << column_id++ << ": " << elem << std::endl;
};
// Read the choosen cols
return read_columns_of_csv(stream, read_wanted_columns(column_id));
}
int main(int argc, char* argv[])
{
// Manage errors for filename
if (argc < 2)
{
std::cerr << "Please specify a filename" << std::endl;
return -1;
}
std::ifstream file(argv[1]);
if (!file)
{
std::cerr << "Invalid filename: " << argv[1] << std::endl;
return -2;
}
// Process
Results results{read_csv(file)};
// Output
unsigned long line = 1;
std::cout << "Results: " << results.size() << " lines" << std::endl;
for (Fields fields: results)
{
std::cout << line++ << ": ";
std::copy(fields.begin(), fields.end(),
std::ostream_iterator<std::string>(std::cout, ","));
std::cout << std::endl;
}
return 0;
}
I suggest using a vector of structures.
The structure will allow each row to have a different type.
Your program would take on the following structure:
Read data into a the vector.
Extra necessary fields out of each structure in the vector and write
to new file.
Close all files.