[英]Regex can't differentiate between float and int types
I have written regexes for recognizing float and int but they don't seem to work (code below).我已经编写了用于识别 float 和 int 的正则表达式,但它们似乎不起作用(下面的代码)。
{
string sumstring = "12.098";
Regex flt = new Regex(@" ^[0-9]*(\.[0-9]*)");
Regex ent = new Regex("^[0-9]+");
if (d_type.IsMatch(sumstring))
{
Console.WriteLine(sumstring + " " + "dtype");
}
Match m = ent.Match(sumstring);
if (m.Success)
{
Console.WriteLine("int");
}
else if (flt.IsMatch(sumstring))
{
Console.WriteLine("float");
}
}
Where is the mistake?错误在哪里?
First, I don't think regular expressions are really the best tool for this job.首先,我不认为正则表达式真的是这项工作的最佳工具。 I would simply use the Double.TryParse()
and Int32.TryParse()
functions.我会简单地使用Double.TryParse()
和Int32.TryParse()
函数。
Second, you're missing a whole lot of test cases with your regular expressions:其次,您的正则表达式遗漏了很多测试用例:
All of these (except maybe the edge case) would be immediately covered by using the library instead of hand-rolling a regex.所有这些(可能除了边缘情况)都将通过使用库而不是手动滚动正则表达式来立即涵盖。
You're trying your tests in the wrong order -- switch them, or (*) put a $ at the end of your RE patterns, to ensure they match all the way to the end.您正在以错误的顺序尝试测试 - 切换它们,或者 (*) 在 RE 模式的末尾放置一个 $,以确保它们一直匹配到最后。
(*) depends on what you're trying to do, exactly: match strings that start with the representation of an integer or float, or, only strings that are entirely composed of such a representation? (*) 完全取决于您要执行的操作:匹配以 integer 或浮点数的表示形式开头的字符串,或者仅匹配完全由此类表示形式组成的字符串?
The "ent" regex should be anchored: Regex ent = new Regex("^[0-9]+$");
“ent”正则表达式应该被锚定: Regex ent = new Regex("^[0-9]+$");
You were matching just the first numbers...你只匹配了第一个数字......
I don't know how compatible C#'s regular expressions are with Perl's, but I try not to reinvent the wheel unless it need reinventing:我不知道 C# 的正则表达式与 Perl 的兼容性如何,但我尽量不重新发明轮子,除非它需要重新发明:
% perl -e 'use Regexp::Common; print $RE{num}{real}, "\n"'
(?:(?i)(?:[+-]?)(?:(?=[0123456789]|[.])(?:[0123456789]*)(?:(?:[.])(?:[0123456789]{0,}))?)(?:(?:[E])(?:(?:[+-]?)(?:[0123456789]+))|))
Now, I don't get why they didn't use [0-9], but this works well.现在,我不明白他们为什么不使用 [0-9],但这很有效。
the regex should have to match the entire string.正则表达式必须匹配整个字符串。 "^\d*\.\d*$"
would match. "^\d*\.\d*$"
会匹配。 Alternatively you can just search for a period in the string.或者,您可以只搜索字符串中的句点。
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