用于提取具有介于和结束模式之间的两个数字的正则表达式

Question

I need to extract two numbers under certain conditions: cumulativelly, the first one need to be followed by a /A , AND the second one must be followed by a B . For instance:

• 30A/305B : both 30 and 305 must be returned;
• 30/305B : neither 30 nor 305 would be returned;
• 30A/305 : neither 30 nor 305 would be returned;

As per here , I tried the regex below without success:

(\d+(?=A\/))(\d+(?=B))

How do I get it done? I am using R , with option perl = TRUE .

Answer 1

The pattern (\\d+(?=A\\/))(\\d+(?=B)) matches 1 or more digits, and asserts (not match) A/ directly to the left.

That first assertion will be true, but after this assertion there is a second part that starts with matching 1 or more digits again.

That can not work, as the previous assertion just asserted that there is A/

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You don't need any lookarounds or perl = TRUE, you can use 2 capture groups instead:

(\d+)A/(\d+)B

Regex demo

str <- "30A/305B: both 30 and 305 must be returned;"
str_match(str, "(\\d+)A/(\\d+)B")

Output

     [,1]       [,2] [,3] 
[1,] "30A/305B" "30" "305"