I came across this in Golang and the result is not so obvious to me, here is the code:
package main
import "fmt"
func main() {
a := 'a'
b := a | 'b'
fmt.Println(b)
}
Does it print a? Does it print b?
No, the result in the console is 99, why?
After upgrading my OSX El Capitánto the new version macOS Sierra, I get this error when trying to run any git command, for example when running:
git status
I get the following error:
xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
Any ideas what I can do about it?
From the original SO question How to replace all occurrences of a string in JavaScript?
For example, if I have a string like this:
var str = "Test abc test test abc test test test abc test test abc";
and I do:
str = str.replace('abc', '');
It only removes the first occurrence of abc, how do I remove all substrings abc?
Driving arraysin Go I realize that there are two ways to declare them.
form 1
When I declare the array with the fixed size
var a [5]int
a[0] = 1
The above does not give any problem.
form 2
When I declare the array without the size.
var b []int
The above does not give any problem, but when I try to assign a value to it, like so:
b[0] = 1
I get this error:
panic: runtime error: index out of range
goroutine 1 [running]:
panic(0x5fb80, 0xc82000a0a0)
/usr/local/go/src/runtime/panic.go:464 +0x3e6
main.main()
/Users/my/path/main.go:8 +0x38
exit status 2
Why do I get that error?
You'll notice that the error message is a bit confusing since it talks about goroutines, which I'm not using yet (I don't even know what they are, I just know they exist).
While reading I found this expression:
_=$=+[],++_+''+$
Curiously, it is a valid expression in javascriptbut the most curious thing is that when it is executed, the result is:
10
I tried to make sense of it by breaking the expression down but I didn't get much done.
Why is the result of that expression equal to 10?
I am doing unit tests on Goand according to some examples a test function is defined like this:
func TestAlgo(t *testing.T) {
...
}
What I want to know is what exactly does the parameter of that function mean?
I've also seen them do something like:
func TestAlgo(*testing.B) {
...
}
What is the difference with the previous parameter?
I'm reading about the special cases of funciones flecha (arrow functions) in javascript and came across an example that I couldn't run.
The example is:
[[1,2], [3,4]].map(([a,b]) => a + b);
which if we try to print it to the console should give us this result:
console.log([[1,2], [3,4]].map(([a,b]) => a + b));
//[ 3, 7 ] <== resultado
The problem is that when trying to execute that line, I get the following error:
console.log([[1,2], [3,4]].map(([a,b]) => a + b));
^
SyntaxError: Unexpected token [
at exports.runInThisContext (vm.js:53:16)
at Module._compile (module.js:374:25)
at Object.Module._extensions..js (module.js:405:10)
at Module.load (module.js:344:32)
at Function.Module._load (module.js:301:12)
at Function.Module.runMain (module.js:430:10)
at startup (node.js:141:18)
at node.js:1003:3
I am using strict mode:
'use strict';
I have done the tests with these versions of node (on OSX):
5.4.0
5.0.0
4.3.0
4.0.0
In all cases, the result has been the same, why?
I'm learning Go( golang ) and found that I don't understand this syntax in variable or constant declaration. For example:
const (
Big = 1 << 100
Small = Big >> 99
)
What exactly does this mean?
I have come across this many times: .PHONYat the end of files Makefileand would like to know what it means. I have used Makefilesbut never needed to add that.
A concrete example of what I found now:
.PHONY: \
all \
test \
clean \
release
I have been trying to extract part of a text (a header) for a long time in bash scriptbut I have not succeeded, this is what I have:
link: <https://api.some.com/v1/monitor/zzsomeLongIdzz?access_token=xxSomeLongTokenxx==>; rel="monitor",<https://api.some.com/v1/services/xx/something-more/accounts/2345?access_token=xxSomeLongTokenxx==>; rel="parent"
Here with a little format so you can see it better
link:
<https://api.some.com/v1/monitor/zzsomeLongIdzz?access_token=xxSomeLongTokenxx==>;
rel="monitor",
<https://api.some.com/v1/services/xx/something-more/accounts/2345?access_token=xxSomeLongTokenxx==>;
rel="parent"
I need the second part, just the url, basically the values between ,<and >; rel="parent"and assign that to a variable, something like:
my_url = $(echo $complete_header) <== aplicarle alguna forma de filtro
I have no idea how to apply a pattern or regex to it to extract the data I need. Before I used jqto filter json, something like:
error_message=$(echo $response | jq '.["errors"]|.[0]|.["message"]')
Unfortunately for me this is not json.
Can anyone help me go in the right direction to my question?
If the solution were with regex, I would like you to give me a summary of what said regex means, enough to be able to modify it.
By mistake I added some files that I didn't want to add to a commit, I did this:
git add .
The thing is, that added all the files in the folder and there are a couple of files that I didn't want to commit because they were for my tests.
When I do this:
git status
I get:
archivo1.js
archivo2.js
archivoQueNoQuieroCommitear.js
Ask
Since I haven't done commithow do I remove archivoQueNoQuieroCommitear.jsfrom the commit?
If possible I am trying to reset the head.
The files didn't exist before so I can't do them checkout.
When you create a docker containerthere is no way to assign resources to it like RAM, disco duro, etc. The only thing I have seen is how to open ports so that there is communication with the outside ( see here ) and also how to add volumes ( see here ) to store or read files.
But I haven't found a way to manage the resources of a docker container, does anyone know if that's possible? are there default values? Do they grow automatically depending on demand? can they be restricted?
I've searched the official documentation but haven't found anything related.
Recently, with the departure of ECMAScript 2015 , the use of the reserved word was introduced, constwhich I understand is for constants.
I have tried it with some variables and everything works very well, like this:
'use strict';
const PI = 3.141516;
PI = 3.14;
console.log(PI);
Which returns the following error:
TypeError: Assignment to constant variable.
That is completely expected in a constant, but my doubt arises when I do the same thing with an object, like so:
const empleado = {
nombre: 'Juan',
profesion: 'Programador'
};
empleado.nombre = 'Pedro';
console.log(empleado);
Which to my surprise returns the object with the nombremodified node, like this:
{ nombre: 'Pedro', profesion: 'Programador' }
Ask
Shouldn't I get the same error when trying to modify an object that has been declared as a constant?
Using node.js, in package.jsonyou can see in the dependencies the name and the version number, something like this:
"dependencies": {
"jshint": "^2.8.0"
}
Note that the symbol appears ^(I don't know the name in Spanish but apparently in English it is called caret ).
However, in other repositories dependencies appear with another symbol, like this:
"dependencies": {
"jshint": "~1.8.0"
}
Note that now the symbol that precedes the version number is ~(in English they call it tilde and in Spanish virgulilla ).
I have also seen repositories with dependencies without either symbol, something like this:
"dependencies": {
"jshint": "1.8.0"
}
What is the difference between these symbols and what do they mean in the package.json?
I'm working on nodejs (although my question is valid for javascript in general) and I stumbled upon something I don't understand.
It is related to the ternary operator which , as I understand it, works like this:
var numero = 5;
var positivo = numero >= 0 ? true : false;
If the condition ( numero >=0) is true, the final result will be the first value that appears after that condition, in this case true. Otherwise, the final result will be the second value, in this case false.
So when printing:
console.log(positivo); //imprime true
If I change the variable numero, I can get a false value:
var numero = -1;
var positivo = numero >= 0 ? true : false;
console.log(positivo); //imprime false
So far so good, but trying to isolate my problem I made this little code snippet:
var isValid = false;
var message;
if(isValid){
message = 'es válida';
}else {
message = 'no es válida';
}
console.log("Ésta condición " + message);
console.log("Ésta condición " + isValid ? 'es válida' : 'no es válida');
According to my logic, since in my code the variable isValidis false, both messages should print:
Ésta condición no es válida
However when I run my program the result is this:
Ésta condición no es válida
es válida
As you can see, when using the ternary operator it ignored for some reason that my variable isValidwas in false, does anyone have an idea why this is happening? And if it was an expected behavior (which I doubt) I'd like to know why.
A co-worker created a branchcall feature/validateEmail. I want to do pullor checkoutof that branchon my machine so I can work on it but not wait for it to do mergea developor a master.
I have tried without success:
git checkout feature/validateEmailgit checkout validateEmailgit pull feature/validateEmailgit pull validateEmailAnd since I use the plugin Ioh my zsh also tried:
gco feature/validateEmailgco validateEmailbranchI can see it with :
gba(by plugin)git branch -aHow can I pull or checkout the remote repository on my machine?
I am trying to provision a Vagrantcon machine Puppetusing this mysql module .
It Hola mundo's simple, it's something like this:
class { '::mysql::server':
root_password => 'strongpassword',
remove_default_accounts => true
}
However, my goal is that after doing Vagrant upthe first time, a machine is built vagrantwith a server mysqlready to be accessed from the machine hostand accept connections from a defined user.
My attempt is the following:
class { '::mysql::server':
root_password => 'strongpass',
remove_default_accounts => false,
override_options => {
mysqld => { bind-address => '0.0.0.0'} //permitir conexiones entrantes desde cualquier ip
}
}
//crear una base de datos llamada `mydb`, un usuario y asignarle una contraseña
mysql::db { 'mydb':
user => 'admin',
password => 'secret',
host => '192.168.33.1',
}
//asignarle todos los permisos al usuario que acabamos de crear
mysql_grant { '[email protected]/*.*':
ensure => 'present',
options => ['GRANT'],
privileges => ['ALL'],
table => '*.*',
user => '[email protected]',
}
To test that everything works as expected I do my tests like this:
vagrant destroyvagrant upThe strange thing is that, when I try to connect, the machine vagrantdoes not allow me but if I do a re-provision vagrant reload --provisionthen I can already connect and do anything consultafrom MySQLWorkbech. What am I doing wrong?