== comparison of string literals, and their usage

[diniz]

Le 06/04/2019 à 21:47, lithium iodate via Digitalmars-d-learn a écrit :
> On Saturday, 6 April 2019 at 15:35:22 UTC, diniz wrote:
>> So, I still could store and use and compare string pointers myself [1], and 
>> get valid results, meaning: pointer equality implies (literal) string 
>> equality. Or am I wrong? The point is, the parser, operating on an array of 
>> prescanned lexemes,  will constantly check whether a valid lexeme is present 
>> simply by checking the lexeme "class". I don't want that to be a real string 
>> comp, too expesensive and for no gain.
>>
>> [1] As in the second comp of your example:
>> void main()
>> {
>>     auto c2 =  "one" == "two";
>>     auto c1 =  "one".ptr is "two".ptr;
>> }
> 
> Not quite. D-strings strictly consist of pointer *and* length, so you need to 
> compare the .length properties as well to correctly conclude that the strings 
> equal. You can concisely do that in one go by simply `is` comparing the array 
> references as in
> 
> string a = "hello";
> string b = a;
> assert(a is b);
> assert(a[] is b[]);
> 
> Of course, if the strings are never sliced, you can just compare the pointers 
> and be done, just make sure to document how it operates. Depending on the 
> circumstances I'd throw in some asserts that do actual strings comparison to 
> verify the program logic.

Thank you very much! And yes, properly documenting is also important to me.
-- 
diniz {la vita e estranj}