range-checking | 易学教程

Is it more efficient to perform a range check by casting to uint instead of checking for negative values?

阅读更多关于 Is it more efficient to perform a range check by casting to uint instead of checking for negative values?

I stumbled upon this piece of code in .NET's List source code : // Following trick can reduce the range check by one if ((uint) index >= (uint)_size) { ThrowHelper.ThrowArgumentOutOfRangeException(); } Apparently this is more efficient (?) than if (index < 0 || index >= _size) I am curious about the rationale behind the trick. Is a single branch instruction really more expensive than two conversions to uint ? Or is there some other optimization going on that will make this code faster than an additional numeric comparison? To address the elephant in the room: yes, this is micro optimization,

How to determine a date in between Friday and Sunday of the week at a particular time

阅读更多关于 How to determine a date in between Friday and Sunday of the week at a particular time

问题 I'm trying to check a current date and time is in between Friday 17:42 and Sunday 17:42 of the week with Java. At the moment I'm doing this with really really bad code block. It was a hurry solution. Now I'm refactoring but I couldn't find any method in joda or etc. Any ideas? Thanks private final Calendar currentDate = Calendar.getInstance(); private final int day = currentDate.get(Calendar.DAY_OF_WEEK); private final int hour = currentDate.get(Calendar.HOUR_OF_DAY); private final int minute

Check if an Edit Text that only accepts number is not empty and the number is equal or less than 100

阅读更多关于 Check if an Edit Text that only accepts number is not empty and the number is equal or less than 100

问题 I'm building an application for receiving grades and I want to make sure that the Edit Texts are not empty and the values are less or equal to 100 I wrote this line but it crashes the application if(Integer.parseInt(editText.gettext().toString()) > 100 || editText.getText().toString().trim().length() == 0) { //Error message for example } and this is the logCat 09-04 18:21:06.331 8649-8649/com.example.nima.myapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.nima

Switch off Delphi range checking for a small portion of code only

阅读更多关于 Switch off Delphi range checking for a small portion of code only

问题 How can one switch off range checking for a part of a file. Switching off is easy, but how do I revert to the project setting later on? The pseudo-code below should explain it: Unit1; //here's range checking on or off as per the project setting code here... {$R-} //range checking is off here because the code causes range check errors code here... //now I want to revert to the project setting. How do I do that? code here... end. 回答1: See: IFOPT directive. {$IFOPT R+} {$DEFINE RANGEON} {$R-} {

Is it more efficient to perform a range check by casting to uint instead of checking for negative values?

阅读更多关于 Is it more efficient to perform a range check by casting to uint instead of checking for negative values?

问题 I stumbled upon this piece of code in .NET's List source code: // Following trick can reduce the range check by one if ((uint) index >= (uint)_size) { ThrowHelper.ThrowArgumentOutOfRangeException(); } Apparently this is more efficient (?) than if (index < 0 || index >= _size) I am curious about the rationale behind the trick. Is a single branch instruction really more expensive than two conversions to uint ? Or is there some other optimization going on that will make this code faster than an