There is an expression "ab" -> add (str (normal ('a')), normal ('b')) in the Some examples section but this expession gives "(ab)" instead of "ab".

Could someone explain this above?

Why the following code in c++ produced the following output? Is this correct?

code:

std::cout << pretty( add(any(), normal('a'))) << std::endl;

std::cout << pretty( add(normal('a'), any())) << std::endl;

std::cout << pretty( add(normal('a'), normal('b'))) << std::endl;

std::cout << pretty( add(normal('b'), normal('a'))) << std::endl;

output:

.

a

a

b

Is this ok?

Thanks for the anwser.
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All test are for positive numbers.
How about negative numbers?

What if v will be consist negative only, it is works?

Also I have the same problem as decribed below:
Test Results:
POSTFIX
STDERR:
solution: virtual void POSTFIX::TESTS(): Assertion `to_postfix(infix) == postfix' failed.
Signal:
Process exited prematurely with a SIGABRT signal.

How to block CTRL+S key shortcut?
I do not need run any tests by this stupit CTRL+S.