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Abort makefile if variable not set
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TL;DR: Use the error function:
ifndef MY_FLAG
$(error MY_FLAG is not set)
endif
Note that the lines must not be indented. More precisely, no tabs must precede these lines.
Generic solution
In case you're going to test many variables, it's worth defining an au...
Is it possible to make abstract classes in Python?
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# Python 2
from abc import ABCMeta, abstractmethod
class Abstract:
__metaclass__ = ABCMeta
@abstractmethod
def foo(self):
pass
Whichever way you use, you won't be able to instantiate an abstract class that has abstract methods, but will be able to instantiate a subclass th...
How to shuffle a std::vector?
...#include <algorithm>
#include <random>
auto rng = std::default_random_engine {};
std::shuffle(std::begin(cards_), std::end(cards_), rng);
Live example on Coliru
Make sure to reuse the same instance of rng throughout multiple calls to std::shuffle if you intend to generate different p...
Make a link open a new window (not tab) [duplicate]
...he anchor element's attribute target[1]. The value you are looking for is _blank[2].
<a href="www.example.com/example.html" target="_blank">link text</a>
JavaScript option
Forcing a new window is possible via javascript - see Ievgen's excellent answer below for a javascript solution...
How to get the python.exe location programmatically? [duplicate]
...ded python environment. My suggestions is to deduce it from
import os
os.__file__
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Java abstract interface
...ared" abstract?
It's not.
public abstract interface Interface {
\___.__/
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'----> Neither this...
public void interfacing();
public abstract boolean interfacing(boolean really);
\___.__/
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'----> nor this, are ne...
Saving a Numpy array as an image
...Scipy. An alternative a few comments below is to use imageio.imwrite('image_file.jpg', array)
– Psi-Ed
May 3 at 6:17
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Debugging in Clojure? [closed]
...race) java.io.FileNotFoundException: Could not locate closure/contrib/trace__init.class or closure/contrib/trace.clj on classpath: (NO_SOURCE_FILE:0)
– LarsH
Sep 3 '10 at 20:49
2
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Change SVN repository URL
...URL to non-SSH or vice versa, for example: svn switch --relocate svn+ssh://_svn_server_/_svn_project_/_svn_branch_ svn://_svn_server_/_svn_project_/_svn_branch_. The last is especially helpful if you do automated checkout as svn+ssh on several nodes using Jenkins API and some of them (Windows nodes)...
Inject errors into already validated form?
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Form._errors can be treated like a standard dictionary. It's considered good form to use the ErrorList class, and to append errors to the existing list:
from django.forms.utils import ErrorList
errors = form._errors.setdefault("m...