How to check if string contains at least one character? I want to eliminate strings where are only special characters, so I've decided that the easiest way is to check if there is at least one character or digit, so I've created [a-zA-Z0-9]{1,} and [a-zA-Z0-9]+ but none of these work.
boost::regex noSpecialCharacters("[a-zA-Z0-9]+");
boost::regex noSpecialCharacters2("[a-zA-Z0-9]{1,}");
string tab[SIZE] = {"father", "apple is red"};
for (int i = 0; i < SIZE; i++) {
if (!boost::regex_match(tab[i], noSpecialCharacters)) {
puts("This is it!");
} else {
puts("or not");
}
if (!boost::regex_match(tab[i], noSpecialCharacters2)) {
puts("This is it!");
} else {
puts("or not");
}
}
for "apple is red" the answer is correct but for "father" it doesn't work.
apple is red won't match because, as per here (my bold):
Note that the result is true only if the expression matches the whole of the input sequence.
That means the spaces make it invalid. It then goes on to say (again, my bold):
If you want to search for an expression somewhere within the sequence then use regex_search.
If all you're looking for is one valid character somewhere in there, you can just use regex_match() with ".*[a-zA-Z0-9].*" or regex_search() with "[a-zA-Z0-9]".
Related
I'm trying to evaluate a string against a set list of parameters with RegExp in Flutter. For example, the string must contain at least:
One capital letter
One lowercase letter
One number from 0-9
One special character, such as $ or !
This is basically for a password entry field of an application. I have set things up, firstly using validateStructure as follows:
abstract class PasswordValidator {
bool validateStructure(String value);
}
Then, I have used the RegExp function as follows:
class PasswordValidatorSpecial implements PasswordValidator {
bool validateStructure(String value) {
String pattern =
r'^(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9])(?=.*?[!##\$&*~£]).{8,}$';
RegExp regEx = new RegExp(pattern);
return regEx.hasMatch(value);
}
}
This does work well, in a sense that when I pass a string/password through it, it does tell me if at least one of the criteria is not met. However, what I would like to do is for the output to be more specific, telling me which of those criteria isn't met.
For example, if the password were to have everything but a number (from 0-9) I would want to be able to get the output to specifically say that a number is missing, but everything else is present.
How would I adapt my code to be able to do that? I thought perhaps by using conditional 'if' statement, although I don't know how that would work. Thanks!
That's right, you can use RegExr to check your RegExp, separate each part and use them separately to have a custom error. Also instead of return a bool value, you can return a String value, such as the following function:
String validateStructure(String value) {
String patternUpperCaseCharacters = r'^(?=.*?[A-Z])';
String patternLowerCaseCharacters = r'^(?=.*?[a-z])';
String patternNumbers = r'^(?=.*?[0-9])';
String patternSpecialCharacters = r'^(?=.*?[!##\$&*~£])';
RegExp regEx = new RegExp(patternUpperCaseCharacters);
if (regEx.hasMatch(value)) {
regEx = new RegExp(patternLowerCaseCharacters);
if (regEx.hasMatch(value)) {
return "More errors";
} else {
return "You need at least one lowercase letter";
}
} else {
return "You need at least one capital letter";
}
}
I want to replace substring within a string,
For eg: the string is aa0_aa1_bb3_c*a0_a,
so I want to replace the substring a0_a with b1_a, but I dont want aa0_a to get replaced.
Basically, no alphabet should be present before and after the substring "a0_a" (to be replaced).
That's what regexes are good at. It exists in standard library since C++11, if you have an older version, you can also use Boost.
With the standard library version, you could do (ref):
std::string result;
std::regex rx("([^A-Za-Z])a0_a[^A-Za-Z])");
result = std::regex_replace("aa0_aa1_bb3_c*a0_a", rx, "$1b1_a$2");
(beware: untested)
Easy enough to do if you loop through each character. Some pseudocode:
string toReplace = "a0_a";
for (int i = 0; i < myString.length; i++) {
//filter out strings starting with another alphabetical char
if (!isAlphabet(myString.charAt(i))) {
//start the substring one char after the char we have verified to be not alphabetical
if (substring(myString(i + 1, toReplace.length)).equals(toReplace)) {
//make the replacement here
}
}
}
Note that you will need to check for indexing out of bounds when looking at the substrings.
I am trying to check if string contains elements from different string in specific order.
For example:
large string: thisisstring
small string: hssg
it should return true.
I only figured out how to check if string contains whole other string but not parts.
This is the code that I wrote for checking for now:
if ([largestring rangeOfString:smallstring].location != NSNotFound) {
printf("contains");
}
If there are no more characters to search for from the small string, return true.
Starting from the position after the most recently found character in the large string, do a linear search for the first character from the small string that has not yet been searched for.
If the character was not found, return false.
Start back at 1.
There's no easy way to do this, at least, no built in way that I know of. You would have to iterate through each letter of your small string and find the first letter that matches your large string.
Each time you find a matching letter, you loop to the next smallstring letter, but instead only begin searching at the index after you found the previous letter.
EDIT:
some pseudo code, untested, may have syntax errors:
int foundChar = 0;
for (int l = 0; l < strlen(smallstring); l++)
{
bool found = false;
for (; foundChar < strlen(largestring); foundChar++)
{
if (smallstring[l] == largestring[foundChar])
{
// We break here because we found a matching letter.
// Notice that foundChar is still in scope so we preserve
// its value for the next check.
found = true;
foundChar++; // Increment so the next search starts with the next letter.
break;
}
}
// If we get down here, that means we've searched all of the letters
// and found no match, we can result with a failure to find the match.
if (found == false)
{
return false;
}
}
// If we get here, it means every loop resulted in a valid match.
return true;
I have two vectors, one which holds my regular expressions and one which holds the string in which will be checked against the regular expression, most of them work fine except for this one (shown below) the string is a correct string and matches the regular expression but it outputs incorrect instead of correct.
INPUT STRING
.C/IATA
CODE IS BELOW
std::string errorMessages [6][6] = {
{
"Correct Corparate Name\n",
},
{
"Incorrect Format for Corporate Name\n",
}
};
std::vector<std::string> el;
split(el,message,boost::is_any_of("\n"));
std::string a = ("");
for(int i = 0; i < el.size(); i++)
{
if(el[i].substr(0,3) == ".C/")
{
DCS_LOG_DEBUG("--------------- Validating .C/ ---------------");
output.push_back("\n--------------- Validating .C/ ---------------\n");
str = el[i].substr(3);
split(st,str,boost::is_any_of("/"));
for (int split_id = 0 ; split_id < splitMask.size() ; split_id++ )
{
boost::regex const string_matcher_id(splitMask[split_id]);
if(boost::regex_match(st[split_id],string_matcher_id))
{
a = errorMessages[0][split_id];
DCS_LOG_DEBUG("" << a )
}
else
{
a = errorMessages[1][split_id];
DCS_LOG_DEBUG("" << a)
}
output.push_back(a);
}
}
else
{
DCS_LOG_DEBUG("Do Nothing");
}
st[split_id] = "IATA"
splitMask[split_id] = "[a-zA-Z]{1,15}" <---
But it still outputs Incorrect format for corporate name
I cannot see why it prints incorrect when it should be correct can someone help me here please ?
Your regex and the surrounding logic is OK.
You need to extend your logging and to print the relevant part of splitMask and st right before the call to boost::regex_match to double check that the values are what you believe they are. Print them surrounded in some punctuation and also print the string length to be sure.
As you probably know, boost::regex_match only finds a match if the whole string is a match; therefore, if there is a non-printable character somewhere, or maybe a trailing space character, that will perfectly explain the result you have seen.
What's the easiest way to do an "instring" type function with a regex? For example, how could I reject a whole string because of the presence of a single character such as :? For example:
this - okay
there:is - not okay because of :
More practically, how can I match the following string:
//foo/bar/baz[1]/ns:foo2/#attr/text()
For any node test on the xpath that doesn't include a namespace?
(/)?(/)([^:/]+)
Will match the node tests but includes the namespace prefix which makes it faulty.
I'm still not sure whether you just wanted to detect if the Xpath contains a namespace, or whether you want to remove the references to the namespace. So here's some sample code (in C#) that does both.
class Program
{
static void Main(string[] args)
{
string withNamespace = #"//foo/ns2:bar/baz[1]/ns:foo2/#attr/text()";
string withoutNamespace = #"//foo/bar/baz[1]/foo2/#attr/text()";
ShowStuff(withNamespace);
ShowStuff(withoutNamespace);
}
static void ShowStuff(string input)
{
Console.WriteLine("'{0}' does {1}contain namespaces", input, ContainsNamespace(input) ? "" : "not ");
Console.WriteLine("'{0}' without namespaces is '{1}'", input, StripNamespaces(input));
}
static bool ContainsNamespace(string input)
{
// a namspace must start with a character, but can have characters and numbers
// from that point on.
return Regex.IsMatch(input, #"/?\w[\w\d]+:\w[\w\d]+/?");
}
static string StripNamespaces(string input)
{
return Regex.Replace(input, #"(/?)\w[\w\d]+:(\w[\w\d]+)(/?)", "$1$2$3");
}
}
Hope that helps! Good luck.
Match on :? I think the question isn't clear enough, because the answer is so obvious:
if(Regex.Match(":", input)) // reject
You might want \w which is a "word" character. From javadocs, it is defined as [a-zA-Z_0-9], so if you don't want underscores either, that may not work....
I dont know regex syntax very well but could you not do:
[any alpha numeric]\*:[any alphanumeric]\*
I think something like that should work no?
Yeah, my question was not very clear. Here's a solution but rather than a single pass with a regex, I use a split and perform iteration. It works as well but isn't as elegant:
string xpath = "//foo/bar/baz[1]/ns:foo2/#attr/text()";
string[] nodetests = xpath.Split( new char[] { '/' } );
for (int i = 0; i < nodetests.Length; i++)
{
if (nodetests[i].Length > 0 && Regex.IsMatch( nodetests[i], #"^(\w|\[|\])+$" ))
{
// does not have a ":", we can manipulate it.
}
}
xpath = String.Join( "/", nodetests );