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Abort makefile if variable not set
...ndef conditional, so that a variable defined to an empty value is also considered "undefined". But this is only true for simple variables and explicitly empty recursive variables:
# ifndef and check_defined consider these UNDEFINED:
explicitly_empty =
simple_empty := $(explicitly_empty)
# ifndef a...
Why does the JVM still not support tail-call optimization?
...the Java language actually exposes the stack trace to the programmer.
Consider the following program:
public class Test {
public static String f() {
String s = Math.random() > .5 ? f() : g();
return s;
}
public static String g() {
if (Math.random() > .9)...
How to automatically generate N “distinct” colors?
...arge the colors can start to look similar. I can also imagine evenly subdividing the RGB cube into a lattice and then drawing points. Does anyone know any other methods? I'm ruling out defining a list and then just cycling through it. I should also say I don't generally care if they clash or don't l...
PHP: exceptions vs errors?
...ert a row into a database. It is possible that this call fails (duplicate ID) - you will want to have a "Error" which in this case is an "Exception". When you are inserting these rows, you can do something like this
try {
$row->insert();
$inserted = true;
} catch (Exception $e) {
echo "T...
Why can't I initialize non-const static member or static array in class?
...ws only static constant integral or enumeration types to be initialized inside the class. This is the reason a is allowed to be initialized while others are not.
Reference:
C++03 9.4.2 Static data members
§4
If a static data member is of const integral or const enumeration type, its declaratio...
How do I pass variables and data from PHP to JavaScript?
...aches to do this. Some require more overhead than others, and some are considered better than others.
In no particular order:
Use AJAX to get the data you need from the server.
Echo the data into the page somewhere, and use JavaScript to get the information from the DOM.
Echo the data directly to...
Python (and Python C API): __new__ versus __init__
...t.__init__ reinitialises the object
[3, 4]
As to why they're separate (aside from simple historical reasons): __new__ methods require a bunch of boilerplate to get right (the initial object creation, and then remembering to return the object at the end). __init__ methods, by contrast, are dead sim...
How to get different colored lines for different plots in a single figure?
I am using matplotlib to create the plots. I have to identify each plot with a different color which should be automatically generated by Python.
...
Why should I use core.autocrlf=true in Git?
...
The only specific reasons to set autocrlf to true are:
avoid git status showing all your files as modified because of the automatic EOL conversion done when cloning a Unix-based EOL Git repo to a Windows one (see issue 83 for instance)
and your coding tools somehow depends on a nati...
One DbContext per web request… why?
... echoing Ian: Having a single DbContext for the whole application is a Bad Idea. The only situation where this makes sense is when you have a single-threaded application and a database that is solely used by that single application instance. The DbContext is not thread-safe and and since the DbConte...