If I have these strings:
$string1 = "This book costs €25.99 in our shop."
and on the other side
$string2 = "This book costs 25,99€ in our shop."
How to get the "€25.99" or "25,99€" using preg_match ? How will the code look like?
Please, notice that there are 2 ways of writing the euro symbol. The correct way in EU is to write the symbol after the number like 25,99€ and using comma as desimal separator. However, a lot of US people are stuck to the dollar way (€25.99) and dot as desimal separator.
How to do this check for both cases and get the value with symbol in the cleanest and most effiecient way?
Here's the raw regex: €\d+(?:[,.]\d+)?|\d+(?:[,.]\d+)?€
preg_match ( "/€\d+(?:[,.]\d+)?|\d+(?:[,.]\d+)?€/" , $string1, $matches)
If you want to consider optional spaces between euro and the value, use this:
preg_match ( "/€ ?\d+(?:[,.]\d+)?|\d+(?:[,.]\d+)? ?€/" , $string1, $matches)
agent-j's pattern is on the right track, but I would do something slightly more restrictive:
/€\d+(:?[.,]\d{2})?|\d+(:?[.,]\d{2})?€/
The only difference is that the decimal part is limited to 2 places, if it exists. I don't think you want to allow something like 99,999€, especially since that could mean "99 thousand, 999 euros" if written in the American style.
What I think you're trying to get at in your reference to the cleanest and most efficient way is that the above pattern seems awkward and redundant when you look at it. It's basically the \d+(:?[.,]\d{2})? portion repeated twice, with the € symbol switching sides. This feels wrong, but it isn't. You can't really get around it without bringing in just as much complexity, if not more. Even if you try to get around it with fancy lookarounds, it's going to look something like this:
/^(?=.*€)€?\d+(:?[.,]\d{2})?((?<!€.*)€)?$/
Clearly not an improvement. Sometimes the most obvious solution is the best one, even if it makes you feel dirty.
Note: If you want to get really crazy with it, you can try a variation (caution: untested, and I haven't done much PHP in a while):
$inner = "(:?\d{1,3}(?:([.,])\d{3})*(?:(?!\1)[.,]\d{2})?|\d*(?:[.,]\d{2})?)";
Usage:
preg_match ( "/€" . $inner . "|" . $inner . "€/", $string1, $matches)
That should also accept things like 99,999.99; 999999,99; 9.999.999,99; .99; etc.
Check for both cases:
/([$€]?[\d,]+[$€]?)/
The ? makes the [$€] optional (literally '0 or 1 of...'), so you'd have to check for the degenerate case where there's just a bare number with no currency symbol at all.
Related
Is it possible to match a string of two different lengths with preg_match? And if yes, how?
I’m looking for something like this:
preg_match("/^[a-zA-Z0-9]{13|25}$/", $string);
As in, return true if $string las a length of exactly either 13 or 25 characters.
P.S.: I know that should be {13,25} — {min,max} —, but I’m not interested in matching within an interval.
This is a fast way:
preg_match('/^[a-zA-Z0-9]{13}([a-zA-Z0-9]{12})?$/', $string);
Something like
preg_match("/^([a-zA-Z0-9]{13}|[a-zA-Z0-9]{25})$/", $string);
([a-zA-Z0-9]{13}|[a-zA-Z0-9]{25} alternation matches either of length 13 or 25
Example : http://regex101.com/r/bJ9vV5/1
I know your question was about doing it with regex, but it's generally best practice to avoid regex whenever possible. A few reasons why:
You should benchmark to be certain, but in most cases, built-in functions will out-perform regex.
Regex is not (thoroughly) understood by a lot of coders
Regex is usually less flexible as far as throwing new "business rules" / requirements into the mix. For example, what if you needed to add in a requirement to do something if the length is 13, and something different if it's 25? Or maybe do something if it's right chars but wrong length? You will not be able to code for these things with regex alone (The solution I present below doesn't address these "what ifs" either but the difference here is that you now have ability to separate the stuff as needed)
So here is a non-regex approach.
if ( in_array(strlen($string),array(13,25)) && ctype_alnum($string) ) {
// good
} else {
// bad
}
How could functions similar to PHP's explode and implode be implemented with APL?
I tried to work it out myself and came up with a solution which I'm posting below. I'd like to see other ways that this might be solved.
Pé, the quest for "short" and/or "elegant" solutions to standard-problems in APL is older than PHP and even older than new terminology, such as "explode", "implode" (I think - but I must admit I do not know how old these terms really are...). Anyway, the early APL guys used the term "idiom" for such "solutions to standard problems that fit in one line of APL".
And for some reason, the Finns were especially creative and even started producing a list of these in order to make it easy for newbies. And I find this stuff still useful after 20yrs of doing APL. It is called "FinnAPL" - the Finnish APL idiom library and you can browse it here: https://aplwiki.com/wiki/FinnAPL_idiom_library (BTW, the whole APL Wiki might be interesting to read...)
You may, however, need to be creative with your wording in order to find solutions ;)
And one warning: FinnAPL only works with "classic" (non-nested) data-structures (nested matrices came with "APL2" which is standard these days), so some of the ways they handle data might no longer be "state-of-the-art". (i.e. back in the "old times", CAT BIRD and DOG would have been represented as a 3x4 array, so "implode" of string-array was a simple as ,array,delimeter (but you then had the challenge to remove blanks which were inserted for padding.
Anyway, I'm not sure why I wrote all this - just a few thoughts which came to mind when thinking about my start with APL ;-)
Ok, let me also look at the question. When your delimeter is a single character the APL2ish-idiomatic way of handling this would be something like this:
⎕ml←3 ⍝ "migration-level" (only Dyalog APL) to ensure APL2-compatibility
s←' '
A←s,'BIRD',s,'CAT',s,'DOG' ⍝ note that delimeter also used as 1st char!
exploded_string←1↓¨(+\A=s)⊂A ⍝ explode
imploded←∊s,¨exploded_string
A≡imploded ⍝ test for successfull round-trip should return 1
Explode:
Given the following text string and delimiter string:
F←'CAT BIRD DOG'
B←' '
Explode can be accomplished as follows:
S←⍴,B
P←(⊃~∨/(-S-⍳S)⌽¨S⍴⊂B⍷F)⊂F
P[2] ⍝ returns BIRD
Limitations:
PHP's explode function returns a null array value when two delimiters are adjacent to each other. The code above simply ignores that and treats the two delimiters as if they were one.
The code above also does nothing to handle overlapping delimiters. This is most likely to occur if repeated characters are used for the delimiter. For example:
F←'CATaaaBIRDaaDOG'
B←'aa'
S←⍴,B
P←(⊃~∨/(-S-⍳S)⌽¨S⍴⊂B⍷F)⊂F
P ⍝ returns CAT BIRD DOG
However, the expected result would be CAT aBIRD DOG because it doesn't recognize 'aaa' as the delimiter followed by 'a.' Rather, it treats it as two overlapping delimiters, which end up functioning as a single delimiter. Another example would be 'tat' as the delimiter, in which case, any occurence in the string of 'tatat' would have the same problem.
Overlapping Delimiters:
I have an alternative for the possibility of a single overlap:
S←⍴,B
A←B⍷F
A←(2×A)>⊃+/(-S-⍳S)⌽¨S⍴⊂A
P←(⊃~∨/(-S-⍳S)⌽¨S⍴⊂A)⊂F
The third line of code eliminates any string positions that occur within a distance of S-1 characters from any delimiter position before it. As I said, this only solves the problem for a single overlap. If there are two or more overlaps, the first is recognized as a delimiter, and all the rest are ignored. Here's an example of two overlaps:
F←'CATtatatatBIRDtatDOG'
B←'tat'
S←⍴,B
A←B⍷F
A←(2×A)>⊃+/(-S-⍳S)⌽¨S⍴⊂A
P←(⊃~∨/(-S-⍳S)⌽¨S⍴⊂A)⊂F
P ⍝ returns CAT atatBIRD DOG
The expected result was 'CAT a BIRD DOG,' but it is unable to recognize the final 'tat' as a delimiter because of the overlap. Such a situation would be rare except when repeated characters are used. If the delimiter is 'aa', then 'aaaa' would be considered a double overlap, and only the first delimiter would be recognized.
Implode:
Much simpler:
P←'CAT' 'BIRD' 'DOG'
B←'-'
(⍴,B)↓∊B,¨P
It returns 'CAT-BIRD-DOG' as expected.
An interesting alternative for implode can be accomplished with reduction:
p←'cat' 'bird' 'dog'
↑{⍺,'-',⍵}/p
cat-bird-dog
This technique does not need to explicitly reference the shape of the delimiter.
And an interesting alternative to explode can be done with n-wise reduction:
f←'CATtatBIRDtatDOG'
b←'tat'
b{(~(-⍴⍵)↑(⍴⍺)∨/⍺⍷⍵)⊂⍵}f
CAT BIRD DOG
there have a long articles, I want only remove thousand separator, not a comma.
$str = "Last month's income is 1,022 yuan, not too bad.";
//=>Last month's income is 1022 yuan, not too bad.
preg_replace('#(\d)\,(\d)#i','???',$str);
How to write the regex patterns? Thanks
If the simplified rule "Match any comma that lies directly between digits" is good enough for you, then
preg_replace('/(?<=\d),(?=\d)/','',$str);
should do.
You could improve it by making sure that exactly three digits follow:
preg_replace('/(?<=\d),(?=\d{3}\b)/','',$str);
If you have a look at the preg_replace documentation you can see that you can write captures back in the replacement string using $n:
preg_replace('#(\d),(\d)#','$1$2',$str);
Note that there is no need to escape the comma, or to use i (as there are not letters in the pattern).
An alternative (and probably more efficient) way is to use lookarounds. These are not included in the match, so they don't have to written back:
preg_replace('#(?<=\d),(?=\d)#','',$str);
The first (\d) is represented by $1, the second (\d) by $2. Therefore the solution is to use something like this:
preg_replace('#(\d)\,(\d)#','$1$2',$str);
Actually it would be better to have 3 numbers behind the comma to avoid causing havoc in lists of numbers:
preg_replace('#(\d)\,(\d{3})#','$1$2',$str);
I'm just getting to know regular expressions, but after doing quite a bit of reading (and learning quite a lot), I still have not been able to figure out a good solution to this problem.
Let me be clear, I understand that this particular problem might be better solved not using regular expressions, but for the sake of brevity let me just say that I need to use regular expressions (trust me, I know there are better ways to solve this).
Here's the problem. I'm given a big file, each line of which is exactly 4 characters long.
This is a regex that defines "valid" lines:
"/^[AB][CD][EF][GH]$/m"
In english, each line has either A or B at position 0, either C or D at position 1, either E or F at position 2, and either G or H at position 3. I can assume that each line will be exactly 4 characters long.
What I'm trying to do is given one of those lines, match all other lines that contain 2 or more common characters.
The below example assumes the following:
$line is always a valid format
BigFileOfLines.txt contains only valid lines
Example:
// Matches all other lines in string that share 2 or more characters in common
// with "$line"
function findMatchingLines($line, $subject) {
$regex = "magic regex I'm looking for here";
$matchingLines = array();
preg_match_all($regex, $subject, $matchingLines);
return $matchingLines;
}
// Example Usage
$fileContents = file_get_contents("BigFileOfLines.txt");
$matchingLines = findMatchingLines("ACFG", $fileContents);
/*
* Desired return value (Note: this is an example set, there
* could be more or less than this)
*
* BCEG
* ADFG
* BCFG
* BDFG
*/
One way I know that will work is to have a regex like the following (the following regex would only work for "ACFG":
"/^(?:AC.{2}|.CF.|.{2}FG|A.F.|A.{2}G|.C.G)$/m"
This works alright, performance is acceptable. What bothers me about it though is that I have to generate this based off of $line, where I'd rather have it be ignorant of what the specific parameter is. Also, this solution doesn't scale terrible well if later the code is modified to match say, 3 or more characters, or if the size of each line grows from 4 to 16.
It just feels like there's something remarkably simple that I'm overlooking. Also seems like this could be a duplicate question, but none of the other questions I've looked at really seem to address this particular problem.
Thanks in advance!
Update:
It seems that the norm with Regex answers is for SO users to simply post a regular expression and say "This should work for you."
I think that's kind of a halfway answer. I really want to understand the regular expression, so if you can include in your answer a thorough (within reason) explanation of why that regular expression:
A. Works
B. Is the most efficient (I feel there are a sufficient number of assumptions that can be made about the subject string that a fair amount of optimization can be done).
Of course, if you give an answer that works, and nobody else posts the answer *with* a solution, I'll mark it as the answer :)
Update 2:
Thank you all for the great responses, a lot of helpful information, and a lot of you had valid solutions. I chose the answer I did because after running performance tests, it was the best solution, averaging equal runtimes with the other solutions.
The reasons I favor this answer:
The regular expression given provides excellent scalability for longer lines
The regular expression looks a lot cleaner, and is easier for mere mortals such as myself to interpret.
However, a lot of credit goes to the below answers as well for being very thorough in explaining why their solution is the best. If you've come across this question because it's something you're trying to figure out, please give them all a read, helped me tremendously.
Why don't you just use this regex $regex = "/.*[$line].*[$line].*/m";?
For your example, that translates to $regex = "/.*[ACFG].*[ACFG].*/m";
This is a regex that defines "valid" lines:
/^[A|B]{1}|[C|D]{1}|[E|F]{1}|[G|H]{1}$/m
In english, each line has either A or B at position 0, either C or D
at position 1, either E or F at position 2, and either G or H at
position 3. I can assume that each line will be exactly 4 characters
long.
That's not what that regex means. That regex means that each line has either A or B or a pipe at position 0, C or D or a pipe at position 1, etc; [A|B] means "either 'A' or '|' or 'B'". The '|' only means 'or' outside of character classes.
Also, {1} is a no-op; lacking any quantifier, everything has to appear exactly once. So a correct regex for the above English is this:
/^[AB][CD][EF][GH]$/
or, alternatively:
/^(A|B)(C|D)(E|F)(G|H)$/
That second one has the side effect of capturing the letter in each position, so that the first captured group will tell you whether the first character was A or B, and so on. If you don't want the capturing, you can use non-capture grouping:
/^(?:A|B)(?:C|D)(?:E|F)(?:G|H)$/
But the character-class version is by far the usual way of writing this.
As to your problem, it is ill-suited to regular expressions; by the time you deconstruct the string, stick it back together in the appropriate regex syntax, compile the regex, and do the test, you would probably have been much better off just doing a character-by-character comparison.
I would rewrite your "ACFG" regex thus: /^(?:AC|A.F|A..G|.CF|.C.G|..FG)$/, but that's just appearance; I can't think of a better solution using regex. (Although as Mike Ryan indicated, it would be better still as /^(?:A(?:C|.E|..G))|(?:.C(?:E|.G))|(?:..EG)$/ - but that's still the same solution, just in a more efficiently-processed form.)
You've already answered how to do it with a regex, and noted its shortcomings and inability to scale, so I don't think there's any need to flog the dead horse. Instead, here's a way that'll work without the need for a regex:
function findMatchingLines($line) {
static $file = null;
if( !$file) $file = file("BigFileOfLines.txt");
$search = str_split($line);
foreach($file as $l) {
$test = str_split($l);
$matches = count(array_intersect($search,$test));
if( $matches > 2) // define number of matches required here - optionally make it an argument
return true;
}
// no matches
return false;
}
There are 6 possibilities that at least two characters match out of 4: MM.., M.M., M..M, .MM., .M.M, and ..MM ("M" meaning a match and "." meaning a non-match).
So, you need only to convert your input into a regex that matches any of those possibilities. For an input of ACFG, you would use this:
"/^(AC..|A.F.|A..G|.CF.|.C.G|..FG)$/m"
This, of course, is the conclusion you're already at--so good so far.
The key issue is that Regex isn't a language for comparing two strings, it's a language for comparing a string to a pattern. Thus, either your comparison string must be part of the pattern (which you've already found), or it must be part of the input. The latter method would allow you to use a general-purpose match, but does require you to mangle your input.
function findMatchingLines($line, $subject) {
$regex = "/(?<=^([AB])([CD])([EF])([GH])[.\n]+)"
+ "(\1\2..|\1.\3.|\1..\4|.\2\3.|.\2.\4|..\3\4)/m";
$matchingLines = array();
preg_match_all($regex, $line + "\n" + $subject, $matchingLines);
return $matchingLines;
}
What this function does is pre-pend your input string with the line you want to match against, then uses a pattern that compares each line after the first line (that's the + after [.\n] working) back to the first line's 4 characters.
If you also want to validate those matching lines against the "rules", just replace the . in each pattern to the appropriate character class (\1\2[EF][GH], etc.).
People may be confused by your first regex. You give:
"/^[A|B]{1}|[C|D]{1}|[E|F]{1}|[G|H]{1}$/m"
And then say:
In english, each line has either A or B at position 0, either C or D at position 1, either E or F at position 2, and either G or H at position 3. I can assume that each line will be exactly 4 characters long.
But that's not what that regex means at all.
This is because the | operator has the highest precedence here. So, what that regex really says, in English, is: Either A or | or B in the first position, OR C or | or D in the first position, OR E or | or F in the first position, OR G or '|orH` in the first position.
This is because [A|B] means a character class with one of the three given characters (including the |. And because {1} means one character (it is also completely superfluous and could be dropped), and because the outer | alternate between everything around it. In my English expression above each capitalized OR stands for one of your alternating |'s. (And I started counting positions at 1, not 0 -- I didn't feel like typing the 0th position.)
To get your English description as a regex, you would want:
/^[AB][CD][EF][GH]$/
The regex will go through and check the first position for A or B (in the character class), then check C or D in the next position, etc.
--
EDIT:
You want to test for only two of these four characters matching.
Very Strictly speaking, and picking up from #Mark Reed's answer, the fastest regex (after it's been parsed) is likely to be:
/^(A(C|.E|..G))|(.C(E)|(.G))|(..EG)$/
as compared to:
/^(AC|A.E|A..G|.CE|.C.G|..EG)$/
This is because of how the regex implementation steps through text. You first test if A is in the first position. If that succeeds, then you test the sub-cases. If that fails, then you're done with all those possible cases (or which there are 3). If you don't yet have a match, you then test if C is in the 2nd position. If that succeeds, then you test for the two subcases. And if none of those succeed, you test, `EG in the 3rd and 4th positions.
This regex is specifically created to fail as fast as possible. Listing each case out separately, means to fail, you would have test 6 different cases (each of the six alternatives), instead of 3 cases (at a minimum). And in cases of A not being the first position, you would immediately go to test the 2nd position, without hitting it two more times. Etc.
(Note that I don't know exactly how PHP compiles regex's -- it's possible that they compile to the same internal representation, though I suspect not.)
--
EDIT: On additional point. Fastest regex is a somewhat ambiguous term. Fastest to fail? Fastest to succeed? And given what possible range of sample data of succeeding and failing rows? All of these would have to be clarified to really determine what criteria you mean by fastest.
Here's something that uses Levenshtein distance instead of regex and should be extensible enough for your requirements:
$lines = array_map('rtrim', file('file.txt')); // load file into array removing \n
$common = 2; // number of common characters required
$match = 'ACFG'; // string to match
$matchingLines = array_filter($lines, function ($line) use ($common, $match) {
// error checking here if necessary - $line and $match must be same length
return (levenshtein($line, $match) <= (strlen($line) - $common));
});
var_dump($matchingLines);
I bookmarked the question yesterday in the evening to post an answer today, but seems that I'm a little late ^^ Here is my solution anyways:
/^[^ACFG]*+(?:[ACFG][^ACFG]*+){2}$/m
It looks for two occurrences of one of the ACFG characters surrounded by any other characters. The loop is unrolled and uses possessive quantifiers, to improve performance a bit.
Can be generated using:
function getRegexMatchingNCharactersOfLine($line, $num) {
return "/^[^$line]*+(?:[$line][^$line]*+){$num}$/m";
}
My current one works almost perfectly but it misses out any other digits after a character like - or /.
The Original String is something like:
#!012 , #!02/09#!011 #!04-072
My current one works on stuff like:
$viewedResult = preg_replace('/#!([0-9A-Z]{1,4})/', '${1}', $viewedResult);
This would give me something like:
04-072<br />
but I want the "-072" in the Number2 bit like:
04-072
It could also be able to include /072s:
04/072
Any ideas? Remember that there is a #! in front of the number!
You could use something like:
preg_replace('~#!([0-9A-Z][0-9A-Z/-]{0,5})~', '${1}', $viewedResult);
I would split up the regular expression in two, as I think you want to match something like \d{1..4}[-/]?\d{1..4} where the first and second set of digits total 4. It's probably better just to look for (\d+[-/]/d+) and do a check afterwards if the total digits size is correct, e.g. finding all matches of (\d+) in the result, and programmatically check their length.
In general, I would pay close attention to what exactly is allowed input, and what (error) you will get if the input does not match. Splitting things up will make it much easier to show a correct error message, such as "number of digits in mooring spot incorrect" (which is I presume what this is about).
If you want the value of Number2, then use:
Number2\s*=\s*([^;"]*)[;"]
And then use the first capture group.
Stupid question: why not using this regular expression /#!([0-9A-Z/-]{1,4})/ ?
Side note: the {1,4} blocks you will retrieving the value 04-072 (it's 6 chars long).
Hope that helps :)