Is \d Really Less Efficient Than [0-9] or [0123456789] in Regex?

D's efficiency in regular expression is not as efficient as [0-9]

In the recent discussion, some people questioned the efficiency of using instead of

or

in regular expressions. Unexpectedly, the test in the C#regular expression engine shows that the efficiency of [0123456789] is lower than the other two options. [0-9] d The possible cause of low efficiency d

Unicode number:

contains all unicode numbers, not just the common 0-9. Therefore, analytical non -standard numbers may slow down the speed of regular expression engines.

1. Unnecessary extra function: Including additional functions other than d, it may need more complicated processing. These additional functions affect efficiency.
2. Test results d [0-9] In order to prove this problem, the following tests were performed:

10,000 random string, each string contains 1,000 characters, half of which contain numbers. Each regular expression (

,

,

) Time to process the string spent:

• regular expression	Time	The percentage of time relative to D
  >	00: 00: 00.2141226	100%
  >	00: 00: 00.1357972	63.42%
  >	00: 00: 00.1388997	64.87%

The results show that and
• are significantly better than d in terms of efficiency. [0-9] [0123456789] Conclusion

正则表达式	时间	相对d的时间百分比
d	00:00:00.2141226	100%
[0-9]	00:00:00.1357972	63.42%
[0123456789]	00:00:00.1388997	64.87%

Although can provide a wider number of digital matching functions, it is sacrificed in terms of performance. For key -type applications, it is recommended to use more concise

or [0-9]. [0123456789]

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