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Makefile variable as prerequisite
...
This will cause a fatal error if ENV is undefined and something needs it (in GNUMake, anyway).
.PHONY: deploy check-env
deploy: check-env
...
other-thing-that-needs-env: check-env
...
check-env:
ifndef ENV
$(error ENV is undefined)
endif
(Note t...
How do you track record relations in NoSQL?
...Use the same criteria you would use to denormalize a relational database: if it's more important for data to have cohesion (think of values in a comma-separated list instead of a normalized table), then do it that way.
But this inevitably optimizes for one type of query (e.g. comments by any user ...
Multiple inputs with same name through POST in php
... an indefinite number of physical addresses along with other information. If I simply gave each of those fields the same name across several entries and submitted that data through post, would PHP be able to access it?
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What is float in Java?
...ess precise than a double, the conversion cannot be performed implicitly.
If you want to create a float, you should end your number with f (i.e.: 3.6f).
For more explanation, see the primitive data types definition of the Java tutorial.
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How to play audio?
...
If you don't want to mess with HTML elements:
var audio = new Audio('audio_file.mp3');
audio.play();
function play() {
var audio = new Audio('https://interactive-examples.mdn.mozilla.net/media/examples/t-rex-roar.mp...
Socket.IO - how do I get a list of connected sockets/clients?
... // the default namespace is "/"
, ns = io.of(namespace ||"/");
if (ns) {
for (var id in ns.connected) {
if(roomId) {
var index = ns.connected[id].rooms.indexOf(roomId);
if(index !== -1) {
res.push(ns.connected[id]);
...
How to recursively find the latest modified file in a directory?
...might be hard for sort to keep everything in memory.
%T@ gives you the modification time like a unix timestamp, sort -n sorts numerically, tail -1 takes the last line (highest timestamp), cut -f2 -d" " cuts away the first field (the timestamp) from the output.
Edit: Just as -printf is probably GNU...
Find the max of two or more columns with pandas
....max(axis=1)
>>> df
A B C
0 1 -2 1
1 2 8 8
2 3 1 3
If you know that "A" and "B" are the only columns, you could even get away with
>>> df["C"] = df.max(axis=1)
And you could use .apply(max, axis=1) too, I guess.
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How do I join two lists in Java?
Conditions: do not modifiy the original lists; JDK only, no external libraries. Bonus points for a one-liner or a JDK 1.3 version.
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Android: How can I get the current foreground activity (from a service)?
...e activity, with a low-priority BroadcastReceiver as backup (to raise a Notification if the activity is not on-screen) -- here is a blog post with more on this pattern
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