using a variable in regex cpp

Question

I have a string:

string str1= "hello"; 
string str2="hel";

And I am doing this to see if str1 has str2 in it:

regex e = str2+"*"
 bool x=regex_match(str1,e); 
cout<<x;

I am getting this : error: conversion from 'std::__cxx11::basic_string' to non-scalar type 'std::__cxx11::regex {aka std::__cxx11::basic_regex}' requested regex e = str2+"";

How to use the variable in my regex. Can someone please tell me where am I going wrong? TIA.

what types are str1, str2, hello and hel? How are they defined? Can you provide the complete code that produces the problem? — Galik
– Galik, Commented Feb 22, 2018 at 19:25
@WiktorStribiżew that question is for concatenation of string! — hydra123
– hydra123, Commented Feb 22, 2018 at 19:26
Also note that the regex hel* will match hello, but not for the reason you probably think. — CompuChip
– CompuChip, Commented Feb 22, 2018 at 19:26
In your real code does hello have quotes round it or is it another variable? — Galik
– Galik, Commented Feb 22, 2018 at 19:28

rafix07 · Accepted Answer · 2018-02-22 19:30:10Z

5

Look at reference about constructor of regex

template <class ST, class SA>
explicit basic_regex ( const basic_string<charT,ST,SA>& str, flag_type flags = 
 ECMAScript );

constructor is explicit so you should write

    regex e(str2+"*");

not

    regex e = str2+"*";

answered Feb 22, 2018 at 19:30

rafix07

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