Comparing strings using relational operators C++

Question

How come when comparing strings...

string e = "11" 
string f = "102" 
string s = "8" 


e > s - this statement is false 
f > s - and this is also false

How come those statements are false? And what are the rules when comparing two strings to each other?

Those are string literals, and the comparison will end up being between const char* which is simply comparing pointer addresses, which is useless for what you're probably looking for (lexicographical sorting or maybe numerical sorting?) — Cory Kramer
– Cory Kramer, Commented Nov 7, 2018 at 19:52
std::string values are compared character by character. Imagine replacing characters '0'...'9' with characters 'a'...'j'. "bb" < "i" alphabetically, and same with "bac" < "j". — hyde
– hyde, Commented Nov 7, 2018 at 19:54
Please provide a minimal reproducible example. Details do matter, "11" > "8" is different from string("11") > string("8") — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Nov 7, 2018 at 19:58
taking into account the edit, the duplicate isnt a duplicate anymore. reopened the question — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Nov 8, 2018 at 14:17

Icemanind · Accepted Answer · 2018-11-07 20:00:50Z

2

Using relational operators on strings in C/C++ will simply compare the memory addresses of the strings. Obviously "11" and "8" are occupying 2 different areas of memory, so it could be false, unless the address where "11" is stored happens to be stored in an address greater than "8", but it's random.

Keep in mind that you can use string::compare, however, it's comparing the ASCII code's of the strings. Since "1" (ASCII Code 49) is less than "8" (ASCII Code 56), it will still be false. You need to use stoi to convert the string to an integer, then compare the integers.

edited Nov 7, 2018 at 20:00

answered Nov 7, 2018 at 19:54

Icemanind

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2 Comments

scohe001 Over a year ago

Good answer, but it may be worth mentioning/explaining that even if he were comparing std::string's so that it would compare the string values and not the addresses, "11" would still evaluate to less than "8".

Pete Becker Over a year ago

No need engage in such blatant ASCIIism here. <g> '1' is required to be less than '8' in every character set supported by C or C++ compilers.

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