I am trying to manipulate a string by finding the \ character in the string Find\inHere. However, I can't put that as an input in test.find('\', 0). It won't work and gives me the error "missing terminating character." Is there a way to fix test.find('\', 0)?
string test = "Find\inHere";
int x = test.find('\', 0); // error on this line
cout << x; // x should equal 4
\ is a character used to introduce special characters, for example \n newline, \xDB shows the ASCII character with hexadecimal number DB etc.
So, in order to search this special character, you have to escape it by adding another \, use:
test.find("\\",0);
EDIT : Also, in your first string, it is not written in it "Find\inHere" but "Find" and an error because \inHere isn't a special instruction. So, same way to avoid it, write "Find\\inHere".
Related
Take a look at the following example:
cout << "option 1:
\n option 2:
\n option 3";
I know,it's not the best way to output a string,but the question is why does this cause an error saying that a " character is missing?There is a single string that must go to stdout but it just consists of a lot of whitespace charcters.
What about this:
string x="
string_test";
One may interpret that string as: "\nxxxxxxxxxxxxstring_test" where x is a whitespace character.
Is it a convention?
That's called multiline string literal.
You need to escape the embedded newline. Otherwise, it will not compile:
std::cout << "Hello world \
and stackoverflow";
Note: Backslashes must be immediately before the line ends as they need to escape the newline in the source.
Also you can use the fun fact "Adjacent string literals are concatenated by the compiler" for your advantage by this:
std::cout << "Hello World"
"Stack overflow";
See this for raw string literals. In C++11, we have raw string literals. They are kind of like here-text.
Syntax:
prefix(optional) R"delimiter( raw_characters )delimiter"
It allows any character sequence, except that it must not contain the
closing sequence )delimiter". It is used to avoid escaping of any
character. Anything between the delimiters becomes part of the string.
const char* s1 = R"foo(
Hello
World
)foo";
Example taken from cppreference.
I am trying to write a regular express in Lucee to mimic the JS on the front end. Since Lucee's regex doesn't seem to suppoert unicode how do I do it.
This is the JS
function charTest(k){
var regexp = /^[\u00C0-\u00ff\s -\~]+$/;
return regexp.test(k)
}
if(!charTest(thisKey)){
alert("Please Use Latin Characters Only");
return false;
}
This is what I have tried in Lucee
regexp = '[\u00C0-\u00ff\s -\~]+/';
writeDump(reFind(regexp,"测));
writeDump(reFind(regexp,"test));
I have also tried
regexp = "[\\p{L}]";
but the dump is always 0
EDIT: Give me one second. I think I interpreted your initial JS regex incorrectly. Fixing it.
EDIT 2: It was more than a second. Your original JS regex was:
"/^[\u00C0-\u00ff\s -\~]+$/". This is:
Basic parts of regex:
"/..../" == signifies the start and stop of the Regex.
"^[...]" == signifies anything that is NOT in this group
"+" == signifies at least one of the previous
"$" == signifies the end of the string
Identifiers in the regex:
"\u00c0-\u00ff" == Unicode character range of Character 192 (À)
to Character 255 (ÿ). This is the Latin 1
Extension of the Unicode character set.
"\s" == signifies a Space Character
" -\~" == signifies another identifier for a space character to the
(escaped) tilde character (~). This is ASCII 32-126, which
includes the printable characters of ASCII (except the DEL
character (127). This includes alpha-numerics amd most punctuation.
I missed the second half of your printable Latin basic character set. I've updated my regex and tests to include it. There are ways to shorthand some of these identifiers, but I wanted it to be explicit.
You can try this:
<cfscript>
//http://www.asciitable.com/
//https://en.wikipedia.org/wiki/List_of_Unicode_characters
//https://en.wikipedia.org/wiki/Latin_script_in_Unicode
function charTest(k) {
return
REfind("[^"
& chr(32) & "-" & chr(126)
& chr(192) & "-" & chr(255)
& "]",arguments.k)
? "Please Use Latin Characters Only"
: ""
;
}
// TESTS
writeDump(charTest("测")); // Not Latin
writeDump(charTest("test")); // All characters between 31 & 126
writeDump(charTest("À")); // Character 192 (in range)
writeDump(charTest("À ")); // Character 192 and Space
writeDump(charTest(" ")); // Space Characters
writeDump(charTest("12345")); // Digits ( character 48-57 )
writeDump(charTest("ð")); // Character 240 (in range)
writeDump(charTest("ℿ")); // Character 8511 (outside range)
writeDump(charTest(chr(199))); // CF Character (in range)
writeDump(charTest(chr(10))); // CF Line Feed Character (outside range)
writeDump(charTest(chr(1000))); // CF Character (outside range)
writeDump(charTest("
")); // CRLF (outside range)
writeDump(charTest(URLDecode("%00", "utf-8"))); // CF Null character (outside range)
//writeDump(asc("测"));
//writeDump(asc("test"));
//writeDump(asc("À"));
//writeDump(asc("ð"));
//writeDump(asc("ℿ"));
</cfscript>
https://trycf.com/gist/05d27baaed2b8fc269f90c7c80a1aa82/lucee5?theme=monokai
All the regex does is look at your input string and if it doesn't find a value between chr(192) and chr(255), it will return your chosen string, else it will return nothing.
I think you can access the UNICODE characters below 255 directly. I'll have to test it.
Do you need to alert this function, like the Javascript? If you need to, you can just output a 1 or 0 to determine if this function actually found the character you're looking for.
Aim: to read a string in the form First\nSecond from a file and to print it as
First
Second
Problem: if the string is defined in the code, as in line = "First\nSecond";, then it is printed on two lines; if instead I read it from a file then is printed as
First\nSecond
Short program illustrating the problem:
#include "stdafx.h" // I'm using Visual Studio 2008
#include <fstream>
#include <string>
#include <iostream>
void main() {
std::ifstream ParameterFile( "parameters.par" ) ;
std::string line ;
getline (ParameterFile, line) ;
std::cout << line << std::endl ;
line = "First\nSecond";
std::cout << line << std::endl ;
return;
}
The parameters.par file contains only the line
First\nSecond
The Win32 console output is
C:\blabla>SOtest.exe
First\nSecond
First
Second
Any suggestion?
In C/C++ string literals ("...") the backslash is used to mark so called "escape sequences" for special characters. The compiler translates (replaces) the two characters '\' (ASCII code 92) followed by 'n' (ASCII code 110) by the new-line character (ASCII code 10). In a text file one would normally just hit the [RETURN] key to insert a newline character. If you really need to process input containing the two characters '\' and 'n' and want to handle them like a C/C++ compiler then you must explicitely replace them by the newline character:
replace(line, "\\n", "\n");
where you have to supply a replace function like this:
Replace part of a string with another string (Standard C++ does not supply such a replace function by itself.)
Other escape sequences supported by C/C++ and similar compilers:
\t -> [TAB]
\" -> " (to distinguish from a plain ", which marks the end of a string literal, but is not part of the string itself!)
\\ -> \ (to allow having a backslash in a string literal; a single backslash starts an escape sequence)
The character indicated in a string literal by the escape sequence \n is not the same as the sequence of characters that looks like \n!
When you think you're assigning First\nSecond, you're not. In your source code, \n in a string literal is a "shortcut" for the invisible newline character. The string does not contain \n - it contains the newline character. It's automatically converted for you.
Whereas what you're reading from your file is the actual characters \ and n.
I have the following code to tokenize a string of the format: (1+2)/((8))-(100*34):
I'd like to throw an error to the user if they use an operator or character that isn't part of my regex.
e.g if user enters 3^4 or x-6
Is there a way to negate my regex, search for it and if it is true throw the error?
Can the regex expression be improved?
//Using c++11 regex to tokenize input string
//[0-9]+ = 1 or many digits
//Or [\\-\\+\\\\\(\\)\\/\\*] = "-" or "+" or "/" or "*" or "(" or ")"
std::regex e ( "[0-9]+|[\\-\\+\\\\\(\\)\\/\\*]");
std::sregex_iterator rend;
std::sregex_iterator a( infixExpression.begin(), infixExpression.end(), e );
queue<string> infixQueue;
while (a!=rend) {
infixQueue.push(a->str());
++a;
}
return infixQueue;
-Thanks
You can run a search on the string using the search expression [^0-9()+\-*/] defined as C++ string as "[^0-9()+\\-*/]" which finds any character which is NOT a digit, a round bracket, a plus or minus sign (in real hyphen), an asterisk or a slash.
The search with this regular expression search string should not return anything otherwise the string contains a not supported character like ^ or x.
[...] is a positive character class which means find a character being one of the characters in the square brackets.
[^...] is a negative character class which means find a character NOT being one of the characters in the square brackets.
The only characters which must be escaped within square brackets to be interpreted as literal character are ], \ and - whereby - must not be escaped if being first or last character in the list of characters within the square brackets. But it is nevertheless better to escape - always within square brackets as this makes it easier for the regular expression engine / function to detect that the hyphen character should be interpreted as literal character and not with meaning "FROM x to z".
Of course this expression does not check for missing closing round brackets. But formula parsers do often not require that there is always a closing parenthesis for every opening parenthesis in comparison to a compiler or script interpreter simply because not needed to calculate the value based on entered formula.
Answer is given already but perhaps someone might need this
[0-9]?([0-9]*[.])?[0-9]+|[\\-\\+\\\\\(\\)\\/\\*]
This regex separates floats, integers and arithmetic operators
Heres the trick:
[0-9]?([0-9]*[.])?[0-9]+ -> if its a digit and has a point, then grab the digits with the point and the digits that follows it, if not, just grab the digits.
Sorry if my answer isn't clear, i just learned regex and found this solution by my own by just trial and errors.
Heres the code (it takes a mathematical expression and split all digits and operators into a vector)
NOTE: I don't know if it accepts whitespaces, meaning that the mathematical expression that i worked with had no whitespaces. Example: 4+2*(3+1) and would separate everything nicely, but i havent tried with whitespaces.
/* Separate every int or float or operator into a single string using regular expression and store it in untokenize vector */
string infix; //The string to be parse (the arithmetic operation if you will)
vector<string> untokenize;
std::regex words_regex("[0-9]?([0-9]*[.])?[0-9]+|[\\-\\+\\\\\(\\)\\/\\*]");
auto words_begin = std::sregex_iterator(infix.begin(), infix.end(), words_regex);
auto words_end = std::sregex_iterator();
for (std::sregex_iterator i = words_begin; i != words_end; ++i) {
cout << (*i).str() << endl;
untokenize.push_back((*i).str());
}
Output:
(<br/>
1<br/>
+<br/>
2<br/>
)<br/>
/<br/>
(<br/>
(<br/>
8<br/>
)<br/>
)<br/>
-<br/>
(<br/>
100<br/>
*<br/>
34<br/>
)<br/>
I did a program to remove a group of Characters From a String. I have given below that coding here.
void removeCharFromString(string &str,const string &rStr)
{
std::size_t found = str.find_first_of(rStr);
while (found!=std::string::npos)
{
str[found]=' ';
found=str.find_first_of(rStr,found+1);
}
str=trim(str);
}
std::string str ("scott<=tiger");
removeCharFromString(str,"<=");
as for as my program, I got my output Correctly. Ok. Fine. If I give a value for str as "scott=tiger" , Then the searchable characters "<=" not found in the variable str. But my program also removes '=' character from the value 'scott=tiger'. But I don't want to remove the characters individually. I want to remove the characters , if i only found the group of characters '<=' found. How can i do this ?
The method find_first_of looks for any character in the input, in your case, any of '<' or '='. In your case, you want to use find.
std::size_t found = str.find(rStr);
This answer works on the assumption that you only want to find the set of characters in the exact sequence e.g. If you want to remove <= but not remove =<:
find_first_of will locate any of the characters in the given string, where you want to find the whole string.
You need something to the effect of:
std::size_t found = str.find(rStr);
while (found!=std::string::npos)
{
str.replace(found, rStr.length(), " ");
found=str.find(rStr,found+1);
}
The problem with str[found]=' '; is that it'll simply replace the first character of the string you are searching for, so if you used that, your result would be
scott =tiger
whereas with the changes I've given you, you'll get
scott tiger