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What does the `forall` keyword in Haskell/GHC do?
I'm beginning to understand how the forall keyword is used in so-called "existential types" like this:
8 Answers
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How do I handle too long index names in a Ruby on Rails ActiveRecord migration?
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Provide the :name option to add_index, e.g.:
add_index :studies,
["user_id", "university_id", "subject_name_id", "subject_type_id"],
:unique => true,
:name => 'my_index'
If using the :index option on references in a create_table block, it t...
What does Java option -Xmx stand for? [duplicate]
...it says,
-Xmxn
Specify the maximum size, in bytes, of the memory allocation pool. This value must a multiple of 1024 greater than 2MB. Append the letter k or K to indicate kilobytes, or m or M to indicate megabytes. The default value is 64MB. The upper limit for this value will be approxim...
Switching to a TabBar tab view programmatically?
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Like Stuart Clark's solution but for Swift 3:
func setTab<T>(_ myClass: T.Type) {
var i: Int = 0
if let controllers = self.tabBarController?.viewControllers {
for controller in controllers {
if let nav = controller as? UINavigationController, nav.topViewCont...
Set Additional Data to highcharts series
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Additionally, with this solution, you can even put multiple data as much as you want :
tooltip: {
formatter: function () {
return 'Extra data: <b>' + this.point.myData + '</b><br> Another Data: <b>...
When should null values of Boolean be used?
Java boolean allows values of true and false while Boolean allows true , false , and null . I have started to convert my boolean s to Boolean s. This can cause crashes in tests such as
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Adding an onclick function to go to url in JavaScript?
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@FayazMd not sure what you're trying to do? Usually if it's JavaScript inside the DOM (currenty inside DOM's element a) as a web page you can not control JS behaviour on the next page (where you're redirecting the browser page). When user leaves the page it's done. Unle...
How to find out which version of the .NET Framework an executable needs to run?
... .publickeytoken = (B0 3F 5F 7F 11 D5 0A 3A ) // .?_....:
.ver 2:0:0:0
}
.assembly extern System.Core
{
.publickeytoken = (B7 7A 5C 56 19 34 E0 89 ) // .z\V.4..
.ver 3:5:0:0
}
And using Reflector, looking at the dissambly (still as IL) for each...
Can an Android NFC phone act as an NFC tag?
... a simple old nfc tag? Is there some application I'm not thinking of? Usually, you'd want to emulate something like a transit card, access key, or credit card which would require a secure element (I think, but not sure).
s...
MySQL: @variable vs. variable. What's the difference?
... a procedure variable is reinitialized to NULL each time the procedure is called, while the session-specific variable is not:
CREATE PROCEDURE prc_test ()
BEGIN
DECLARE var2 INT DEFAULT 1;
SET var2 = var2 + 1;
SET @var2 = @var2 + 1;
SELECT var2, @var2;
END;
SET @var2 = 1;
CALL prc...