Comparison Between String Literal

Warning: comparison with string literals results in unspecified behaviour

You want to use strcmp() == 0 to compare strings instead of a simple ==, which will just compare if the pointers are the same (which they won't be in this case).

args[i] is a pointer to a string (a pointer to an array of chars null terminated), as is "&" or "<".

The expression argc[i] == "&" checks if the two pointers are the same (point to the same memory location).

The expression strcmp( argc[i], "&") == 0 will check if the contents of the two strings are the same.

comparison between string literal

char arrays or char pointers aren't really the same thing as string class objects in C++, so this

if (option == "foo")

Doesn't compare the string option to the string literal "foo" it compares the address of option with the address of the string literal "foo". You need to use one of the many string comparison functions if you want to know if the option is the same as "foo". strcmp is the obvious way to do this, or you can use std::string instead of char*

Comparison with string literal results in unspecified behaviour?

In C++ == only implemented internally for primitive types and array is not a primitive type, so comparing char[100] and string literal will only compare them as 2 char* or better to say as 2 pointers and since this 2 pointers can't be equal then items[n] == "ae" can never be true, instead of this you should either use std::string to hold string as:

std::string items[100];
// initialize items
if( items[n] == "ae" ) ...

or you should use strcmp to compare strings, but remeber strcmp return 0 for equal strings, so your code will be as:

char items[100][100];
// initialize items
if( strcmp(items[n], "ae") == 0 ) ...

And one extra note is if (items == 0) is useless, since items allocated on stack and not in the heap!

C++: warning: comparison with string literal results in unspecified behaviour [-Waddress]

Your comparison user->MyClass->name.c_str() == "user" compares two pointers, and two pointers that will never be the same.

Since you seem to be using std::string you can use the equality comparison operator directly without needing to get a pointer:

if (user->MyClass->name == "user") { ... }

If for some strange reason you want to compare using C-style string pointers, you must use std::strcmp.

C++ Comparison of String Literals

You are comparing memory addresses. Apparently your compiler places the string literals in memory in the order it encounters them, so the first is "lesser" than the second.

Since in the first snippet it sees "A" first and "Z" second, "A" is lesser. Since it sees "Z" first in the second, "Z" is lesser. In the last snippet, it already has literals "A" and "Z" placed when the second command rolls around.

What's wrong with the conditions in this IF-ELSE?

userGuess == "h" (and userGuess == "e")

You compare string literals using operator == which is not a valid string comparison in C - you should use standard library function for string comparison strcmp instead¹.

Otherwise, make userGuess as single char variable instead of array of char, and use single character (single quote) for comparison, such as

userGuess == 'h'

¹
As it stands, the comparison userGuess == "h" compiles but should give you an warning if you turn on gcc -Wall compiler flag, for example:

warning: comparison with string literal results in unspecified behavior [-Waddress]

It means (as mentioned by Jonathan Leffler's comment below), you are not comparing the strings itself but instead comparing the two pointers (userGuess and "l" are pointing to the same location) - which is valid but generally meaningless.

Pylint complains about comparing a string to a literal with 'is'

is checks that the left hand argument holds the exact same reference as the right hand argument. This is fine for None which is a singleton, but is usually a bad idea for other types, where multiple instances can have the same logical value.

Consider, e.g. the following example:

>>> my_string = ''.join([c for c in 'xfje'])
>>> print my_string
xfje
>>> print my_string == 'xfje'
True
>>> print my_string is 'xfje'
False