string-concatenation

Please tell me the answer with explanation: #define f(g,h) g##h main(){ printf("%d",f(100,10)); } ## is used to concatenate whatever is before the ## with whatever is after it. It is used for concatenation. You can check the reference for details A ## operator between any two successive identifiers in the replacement-list runs parameter replacement on the two identifiers (which are not macro-expanded first) and then concatenates the result. This operation is called "concatenation" or "token pasting". 来源： https://stackoverflow.com/questions/29577775/what-does-mean-in-the-define-directive-in-the

I know this might be quite basic and probably pretty straight forward but i cannot clearly understand what will happen in this situation, so, here it goes. In the following code: String str1 = "Hello"; String str2 = "World"; String str3 = new String("HelloWorld"); String str4 = str1 + str2; i know that str1 and str2 will create an object "Hello" and "World" respectively inside the String Constant Pool . While for str3 a new object is created outside the String Constant Pool which is pointing to "HelloWorld" that is created inside String Constant Pool . My question is, what will happen if i

Is there any noticeable difference between the two lines? My coworker says that using += is "faster" but I don't see why they should be any different: string s1 = "hello"; string s2 = " world"; // Option 1 s1 += s2; // Option 2 s1.append(s2); To clarify, I am not asking about the usage differences between the two functions - I am aware that append() can be used for a wider variety of uses and that operator += is somewhat more specialized. What I care about is how this particular example gets treated. According to the standard concerning string::op+= / online c++ standard draft , I wouldn't

I'm maintaining an application written in Microsoft Access with VBA. I'm glancing over my code and have just noticed I have subconsciously been concatenating strings together with the plus (+) symbol instead of the ampersand. It's been a few years since I've coded in VB6. Could this cause any issues? Everything seems fine and it will only take a few minutes to fix, I'm just curious as to whether I'm technically doing anything wrong. The ampersand is explicitly a string operation, while the plus is overloaded: Dim num1 As Integer num1 = RandomNumberBetween(1, 9) Dim num2 As Integer num2 =

This question already has an answer here: How to concatenate string variables in Bash 30 answers I am trying to download files from a database using wget and url. E.g. wget " http://www.rcsb.org/pdb/files/1BXS.pdb " So format of the url is as such: http://www.rcsb.org/pdb/files/ ($idnumber).pdb" But I have many files to download; so I wrote a bash script that reads id_numbers from a text file, forms url string and downloads by wget. !/bin/bash while read line do url="http://www.rcsb.org/pdb/files/$line.pdb" echo -e $url wget $url done < id_numbers.txt However, url string is formed as .pdb:/

This question already has an answer here: Apparently not able to append a string to another 1 answer I have the following code, but it doesn't work: CHARACTER*260 xx, yy, zz xx = 'A' yy = 'B' zz = xx // yy When I debug my code in Visual Studio the variable xx contains 'A' variable yy contains 'B' variable zz contains 'A' Why doesn't zz contain 'AB'? Alexander Vogt You defined xx to be 260 characters long. Assigning a shorter character literal will result in a padding with blanks. Thus, xx contains A and 259 blanks. yy contains B and 259 blanks. So the concatenated string would be 'A' + 259