Using REGULAR EXPRESSION to replace string between special characters in oracle - c++

Question

select a[b]c[d][e]f[g] from dual;
I need an output:
acf
i.e. Removed with all [] as well as the text between them .
Solution can be in Oracle or C++ function.
Tried erase function in C++ , something like :
int main ()
{
std::string str ("a[b]c[d]e[f]");
std::cout << str << '\n';
while(1)
{
std::size_t foundStart = str.find("[");
//if (foundStart != std::string::npos)
std::cout << "'[' found at: " << foundStart << '\n';
str.begin();
std::size_t foundClose = str.find("]");
//if (foundClose != std::string::npos)
std::cout << "']' found at: " << foundClose << '\n';
str.begin();
str.erase (foundStart,foundClose);
std::cout << str << '\n';
}
return 0;
}
which returns an output as :
a[b]c[d]e[f]
'[' found at: 1
']' found at: 3
ac[d]e[f]
'[' found at: 2
']' found at: 4
ac[f]
'[' found at: 2
']' found at: 4
ac
'[' found at: 18446744073709551615
']' found at: 18446744073709551615
terminate called after throwing an instance of 'std::out_of_range'
what(): basic_string::erase
Thanks in Advance.

Answer 1

I don't know enough C++ or Oracle to implement it, but the Regular Expression would look something like this, I suppose:
(?<=[\s\]])[a-z](?=(\[[a-z]\])+[\sa-z])
This will match a, c and f.
You will need to iterate over the matches and print them accordingly.
The regular expression is decoupled from whatever text is around the target,
hello there a[b]c[d][e]f[g] way to go! will have the same matches,
just be sure to have spaces around the target string a[b]c[d][e]f[g]
I hope I helped you!
Good luck

Answer 2

You can use regexp_replace(<your_string>,'\[.*?\]')
Breaking down,
\[ --matches single square bracket '['. Should be escaped with a backslash '\', as '[' is regex operator
.*? --non greedy expression to match minimum text possible
\] --matches single square bracket ']'. Should be escaped with a backslash '\', as ']' is regex operator
Example:
SQL> with x(y) as (
select 'a[b]c[d][][e]f[g][he]ty'
from dual
)
select y, regexp_replace(y,'\[.*?\]') regex_str
from x;
Y REGEX_STR
----------------------- -----------
a[b]c[d][][e]f[g][he]ty acfty