C++ empty String constructor

Question

I am a C++ beginner, so sorry if the question is too basic.

I have tried to collect the string constrcturs and try all them out (to remember them).

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Answer 1

This is a very popular gotcha. C++ grammar is ambiguous. One of the rules to resolve ambiguities is "if something looks like declaration it is a declaration". In this case instead of defining a variable you declared a function prototype.

string strA();

is equivalent to

string strA(void);

a prototype of a no-arg function which returns string.

If you wish to explicitly call no-arg constructor try this:

string strA=string();

It isn't fully equivalent - it means 'create a temporary string using no-arg constructor and then copy it to initialize variable strA', but the compiler is allowed to optimize it and omit copying.

EDIT: Here is an appropriate item in C++ FAQ Lite