increment | 易学教程

mysql_fetch_array while loop. How does it work?

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问题 I have read about the function on php.net and that has still not answered my question. I know a beginners amount of C and I've just started using php. Normally in C if you were to do a while loop there needs to be some condition to advance the loop to a point where it will no longer be valid like so: while (x >= 10) { printf("..."; printf("x \n"; x++; } However in my php script that I'm using for a pm message system I have a while loop like this: while($row2 = mysql_fetch_array($query))

JavaScript Calculate brighter colour

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I have a colour value in JS as a string #ff0000 How would I go about programatically calculating a brighter/lighter version of this colour, for example #ff4848 , and be able to calculate the brightness via a percentage, e.g. increase_brightness('#ff0000', 50); // would make it 50% brighter function increase_brightness(hex, percent){ // strip the leading # if it's there hex = hex.replace(/^\s*#|\s*$/g, ''); // convert 3 char codes --> 6, e.g. `E0F` --> `EE00FF` if(hex.length == 3){ hex = hex.replace(/(.)/g, '$1$1'); } var r = parseInt(hex.substr(0, 2), 16), g = parseInt(hex.substr(2, 2), 16), b

incremental indexing lucene

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问题 I'm making an application in Java using Lucene 3.6 and want to make an incremental rate. I have already created the index, and I read that you have to do is open the existing index, and check each document indexing and document modification dates to see if they differ delete the index file and re-add again. My problem is I do not know how to do that in Java Lucene. Thanks My code is: public static void main(String[] args) throws CorruptIndexException, LockObtainFailedException, IOException {

Increment a value in Postgres

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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? 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 condition: UPDATE totals SET total = total + 1 WHERE name = 'bill' AND total = 203; 来源： https://stackoverflow.com

Precedence of ++ and — operators in Java

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问题 I read from the official tutorial of Java that prefix and postfix ++ -- have different precedences: postfix: expr++ expr-- unary: ++expr --expr +expr -expr ~ ! Operators According to the tutorial, shouldn't this d = 1; System.out.println(d++ + ++d); print out 6 ( d++ makes d 2, ++d makes it 3) instead of 4? I know the explanation of ++d being evaluated beforehand, but if d++ has higher precedence then ++d , why isn't d++ being first evaluated? And what is more, in what case should d++ shows

Ruby: How to iterate over a range, but in set increments?

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So I'm iterating over a range like so: (1..100).each do |n| # n = 1 # n = 2 # n = 3 # n = 4 # n = 5 end But what I'd like to do is iterate by 10's. So in stead of increasing n by 1, the next n would actually be 10, then 20, 30, etc etc. See http://ruby-doc.org/core/classes/Range.html#M000695 for the full API. Basically you use the step() method. For example: (10..100).step(10) do |n| # n = 10 # n = 20 # n = 30 # ... end You can use Numeric#step . 0.step(30,5) do |num| puts "number is #{num}" end # >> number is 0 # >> number is 5 # >> number is 10 # >> number is 15 # >> number is 20 # >> number

When to use post increment and pre increment in Java [duplicate]

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问题 This question already has answers here : How do the post increment (i++) and pre increment (++i) operators work in Java? (14 answers) Closed 3 years ago . I understand that there are a number of questions on this topic on StackOverflow. But I am still slightly confused and unsure of when to use the operations. I am going through old tests in studying for my exam. One of the methods returns the number of classrooms that are handicapped accessible and are available. I wrote the counter method

Increment columns in laravel

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问题 Is there a way to increment more than one column in laravel? Let's say: DB::table('my_table') ->where('rowID', 1) ->increment('column1', 2) ->increment('column2', 10) ->increment('column3', 13) ->increment('column4', 5); But this results to: Call to a member function increment() on integer I just want to find an efficient way to do this using the given functions from laravel. Thanks. Any suggestions will do. 回答1: There is no existing function to do this. You have to use update() : DB::table(

SQL atomic increment and locking strategies - is this safe?

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问题 I have a question about SQL and locking strategies. As an example, suppose I have a view counter for the images on my website. If I have a sproc or similar to perform the following statements: START TRANSACTION; UPDATE images SET counter=counter+1 WHERE image_id=some_parameter; COMMIT; Assume that the counter for a specific image_id has value '0' at time t0. If two sessions updating the same image counter, s1 and s2, start concurrently at t0, is there any chance that these two sessions both

Can a for loop increment/decrement by more than one?

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问题 Are there other ways to increment a for loop in Javascript besides i++ and ++i ? For example, I want to increment by 3 instead of one. for (var i = 0; i < myVar.length; i+3) { //every three } 回答1: Use the += assignment operator: for (var i = 0; i < myVar.length; i += 3) { Technically, you can place any expression you'd like in the final expression of the for loop, but it is typically used to update the counter variable. For more information about each step of the for loop, check out the MDN