How to define regular expression of mathematical expression.please define a common regular expression for
5+4
5-3
5*6
6/2
`+` is not a meta character inside a character class - need not be escaped. `-` is a meta character inside a character class and need to be escaped unless it is the first or last character in the class. `^\d+[+*/-]\d+$` or `^\d+[+*\-/]\d+$` or `^\d+[-+*/]\d+$`
Amarghosh
2010-05-28 07:39:31
you are right :) my bad
Itay
2010-05-28 07:41:38
`(\d)+` will match and capture one digit at a time, so only the last digit is retained. If you want to capture the whole number, put the plus sign inside the parens: `(\d+)`; if you don't want to capture it, get rid of the parens because they're just creating a lot of extra work for the regex engine.
Alan Moore
2010-05-28 08:03:49
The regex engines will look up and shout "Save us," and I'll whisper… "No."
jasonmp85
2010-05-28 08:16:15
removed the -1 :)
Amarghosh
2010-05-28 08:16:56
:) For some reason I tend to answer questions even if I don't really familiar with the subject. I hardly use regex in my code :)
Itay
2010-05-28 08:27:13
Don't stop doing that.. that's how you learn - at least that's how I learned regex. Once learned, you'll start looking for a chance to use regex - at least I did.
Amarghosh
2010-05-28 09:53:07
+4
A:
Ok, here's one which might be a bit more complicated than you need (hey, it's a regex!)
/^\s*-?\d+(?:\.\d+)?(?:\s*[+*\/\-]\s*-?\d+(?:\.\d+)?)+(?:\s*=\s*-?\d+(?:\.\d+)?)?$/
It allows for one or more operations, decimal numbers, and optionally an "equals" part at the end.
5 + 7
3 * 2 - 8
80.31 + 12 / 6
5 * 7 - 2 = 33
nickf
2010-05-28 08:18:47
A:
The specification is vague, but here's a readable regex using meta-regexing approach in Java.
String regex =
"num(?:opnum)*"
.replace("op", "\\s*[*/+-]\\s*")
.replace("num", "\\s*[+-]?\\d+(?:\\.\\d+)?\\s*");
String[] tests = {
"5+4", // true
"5 - 3", // true
"5 * 6 - 4", // true
"3.14159 = 0", // true
"A = B", // false
"5+ -4", // true
"5 * +4", // true
"5++5", // true
"5+++5", // false
"5+5+" // false
};
for (String test : tests) {
System.out.println(test + " " + test.matches(regex));
}
Numbers may include optional decimal part, and a +/- sign. There could be multiple equalities.
polygenelubricants
2010-05-28 09:43:42