increment

问题 Is there any reason for Scala not support the ++ operator to increment primitive types by default? For example, you can not write: var i=0 i++ Thanks 回答1: My guess is this was omitted because it would only work for mutable variables, and it would not make sense for immutable values. Perhaps it was decided that the ++ operator doesn't scream assignment, so including it may lead to mistakes with regard to whether or not you are mutating the variable. I feel that something like this is safe to

问题 I want to create an incrementing second timer like a stopwatch. So I want to be able to display the seconds and minutes incrementing in the format 00:01... Google only brings up 24 hour clock examples, I was wondering could anyone get me started with an example or tutorial of what I want to do? Edit: Here is what I have using the Chronometer in Android so far In onCreate() secondsT = 0; elapsedTimeBeforePause = 0; stopWatch.start(); startTime = SystemClock.elapsedRealtime(); stopWatch.setBase

问题 Speaking in the context of the C++11 standard (which no longer has a concept of sequence points, as you know) I want to understand how two simplest examples are defined. int i = 0; i = i++; // #0 i = ++i; // #1 There are two topics on SO which explain those examples within the C++11 context. Here it was said that #0 invokes UB and #1 is well-defined. Here it was said that both examples are undefined. This ambiguity confuses me much. I've read this well-structured reference three times already

问题 I'm a little new to postgres. I want to take a value (which is an integer) in a field in a postgres table and increment it by one. For example if the table 'totals' had 2 columns, 'name' and 'total', and Bill had a total of 203, what would be the SQL statement I'd use in order to move Bill's total to 204? 回答1: UPDATE totals SET total = total + 1 WHERE name = 'bill'; If you want to make sure the current value is indeed 203 (and not accidently increase it again) you can also add another

问题 I have been fooling around with some code and saw something that I don't understand the "why" of. int i = 6; int j; int *ptr = &i; int *ptr1 = &j j = i++; //now j == 6 and i == 7. Straightforward. What if you put the operator on the left side of the equals sign? ++ptr = ptr1; is equivalent to (ptr = ptr + 1) = ptr1; whereas ptr++ = ptr1; is equivalent to ptr = ptr + 1 = ptr1; The postfix runs a compilation error and I get it. You've got a constant "ptr + 1" on the left side of an assignment

问题 This question already has answers here : Closed 8 years ago . Possible Duplicates: Why does this go into an infinite loop? Things like i = i++ have undefined behavior in C and C++ because the value of a scalar object is changes twice within the same expression without intervening sequence point. However I suppose that these kind of expressions have well-defined behavior in C# or Java because AFAIK the evaluation of argument goes left to right and there are sequence points all over. That said,

问题 the following script with debug option 'set -e -v' fails at the increment operator only when the variable has a prior value of zero. #!/bin/bash set -e -v i=1; let i++; echo "I am still here" i=0; let i++; echo "I am still here" i=0; ((i++)); echo "I am still here" bash (GNU bash, version 4.0.33(1)-release (x86_64-apple-darwin10) but also GNU bash, version 4.2.4(1)-release (x86_64-unknown-linux-gnu)) any ideas? 回答1: the answer to my question is not to use let (or shift , or...) but to use i=$

问题 This question already has answers here : How do I create a variable number of variables? (14 answers) Closed last year . In Python, if I were to have a user input the number X, and then the program enters a for loop in which the user inputs X values, is there a way/is it a bad idea to have variable names automatically increment? ie: user inputs '6' value_1 = ... value_2 = ... value_3 = ... value_4 = ... value_5 = ... value_6 = ... Can I make variable names increment like that so that I can

问题 This question already has answers here : How do I create a variable number of variables? (14 answers) Closed last year . In Python, if I were to have a user input the number X, and then the program enters a for loop in which the user inputs X values, is there a way/is it a bad idea to have variable names automatically increment? ie: user inputs '6' value_1 = ... value_2 = ... value_3 = ... value_4 = ... value_5 = ... value_6 = ... Can I make variable names increment like that so that I can

问题 I notice that a pre-increment/decrement operator can be applied on a variable (like ++count ). It compiles, but it does not actually change the value of the variable! What is the behavior of the pre-increment/decrement operators (++/--) in Python? Why does Python deviate from the behavior of these operators seen in C/C++? 回答1: ++ is not an operator. It is two + operators. The + operator is the identity operator, which does nothing. (Clarification: the + and - unary operators only work on