increment

问题 My interest is in the difference between for and while loops. I know that the post-increment value is used and then incremented and the operation returns a constant pre-increment. while (true) { //... i++; int j = i; } Here, will j contain the old i or the post-incremented i at the end of the loop? 回答1: Since the statement i++ ends at the ; in your example, it makes no difference whether you use pre- or post-increment. The difference arises when you utilize the result: int j = i++; // i will

问题 I want to create a non-thread-safe chunk of code for experimentation, and those are the functions that 2 threads are going to call. c = 0 def increment(): c += 1 def decrement(): c -= 1 Is this code thread safe? If not, may I understand why it is not thread safe, and what kind of statements usually lead to non-thread-safe operations. If it is thread-safe, how can I make it explicitly non-thread-safe? 回答1: Single opcodes are thread-safe because of the GIL but nothing else: import time class

问题 This question already has an answer here: Why are these constructs using pre and post-increment undefined behavior? 14 answers int b=0,a=1;b= ++a + ++a; what is the value of b? what is the calculation for it? [duplicate] 2 answers I\'m new to C language so plz sum1 help me out. A C code written int i=3; printf(\"%d\",++i + ++i); Complier gvs O/P =9. How? Thanx in advance 回答1: The results are undefined. You're modifying a variable more than once in an expression (or sequence point to be more

问题 Does anyone know of a Javascript library (e.g. underscore, jQuery, MooTools, etc.) that offers a method of incrementing a letter? I would like to be able to do something like: \"a\"++; // would return \"b\" 回答1: Simple, direct solution function nextChar(c) { return String.fromCharCode(c.charCodeAt(0) + 1); } nextChar('a'); As others have noted, the drawback is it may not handle cases like the letter 'z' as expected. But it depends on what you want out of it. The solution above will return '{'

问题 I am learning C language and quite confused the differences between ++*ptr and *ptr++ . For example: int x = 19; int *ptr = &x; I know ++*ptr and *ptr++ produce different results but I am not sure why is that? 回答1: These statements produce different results because of the way in which the operators bind. In particular, the prefix ++ operator has the same precedence as * , and they associate right-to-left. Thus ++*ptr is parsed as ++(*ptr) meaning "increment the value pointed at by ptr ,". On

问题 With MySQL, if I have a field, of say logins, how would I go about updating that field by 1 within a sql command? I\'m trying to create an INSERT query, that creates firstName, lastName and logins. However if the combination of firstName and lastName already exists, increment the logins by 1. so the table might look like this.. firstName----|----lastName----|----logins John Jones 1 Steve Smith 3 I\'m after a command that when run, would either insert a new person (i.e. Tom Rogers) or

问题 I am looking at Xcode 7.3 notes and I notice this issue. The ++ and -- operators have been deprecated Could some one explain why it is deprecated? And am I right that in new version of Xcode now you going to use instead of ++ this x += 1 ; Example: for var index = 0; index < 3; index += 1 { print(\"index is \\(index)\") } 回答1: A full explanation here from Chris Lattner, Swift's creator. I'll summarize the points: It's another function you have to learn while learning Swift Not much shorter

问题 Why is ++i is l-value and i++ not? 回答1: Well as another answerer pointed out already the reason why ++i is an lvalue is to pass it to a reference. int v = 0; int const & rcv = ++v; // would work if ++v is an rvalue too int & rv = ++v; // would not work if ++v is an rvalue The reason for the second rule is to allow to initialize a reference using a literal, when the reference is a reference to const: void taking_refc(int const& v); taking_refc(10); // valid, 10 is an rvalue though! Why do we

问题 Recently I have come across this problem which I am unable to understand by myself. What do these three Expressions REALLY mean? *ptr++ *++ptr ++*ptr I have tried Ritchie. But unfortunately was unable to follow what he told about these 3 operations. I know they are all performed to increment the pointer/the value pointed to. I can also guess there may be a lot of things about precedence and order of evaluation. Like one increments the pointer first then fetches the content of that pointer,

问题 I have the following code: public class Tests { public static void main(String[] args) throws Exception { int x = 0; while(x<3) { x = x++; System.out.println(x); } } } We know he should have writen just x++ or x=x+1 , but on x = x++ it should first attribute x to itself, and later increment it. Why does x continue with 0 as value? --update Here\'s the bytecode: public class Tests extends java.lang.Object{ public Tests(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object.\"<init>