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How is this fibonacci-function memoized?
...nacci definition, fib n = fib (n-1) + fib (n-2), the function itself gets called, twice from the top, causing the exponential explosion. But with that trick, we set out a list for the interim results, and go "through the list":
fib n = (xs!!(n-1)) + (xs!!(n-2)) where xs = 0:1:map fib [2..]
The tr...
Some built-in to pad a list in python
...
a += [''] * (N - len(a))
or if you don't want to change a in place
new_a = a + [''] * (N - len(a))
you can always create a subclass of list and call the method whatever you please
class MyList(list):
def ljust(self, n, fillvalue=''):
return self + [fillvalue] * (n - len(self))
a...
Force page scroll position to top at page refresh in HTML
... This is the correct answer. The jQuery solution does not work in all cases.
– Harry Stevens
Dec 5 '17 at 18:52
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Why no generics in Go?
... id types. Type information is preserved and can be "cast" (asserted, actually) back to its concrete type. Get the gritty details here: golang.org/ref/spec#Type_assertions
– tbone
Aug 25 '13 at 20:50
...
How to have stored properties in Swift, the same way I had on Objective-C?
...n't work : static var means that the value of the property is the same for all instance
– Fry
Mar 8 '17 at 15:40
@fry ...
Creating functions in a loop
...cated way which involved using a closure as a "function factory":
def make_f(i):
def f():
return i
return f
and in your loop use f = make_f(i) instead of the def statement.
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in_array() and multidimensional array
...sive (hence the _r, analogous to print_r(), for example). It descends into all nested arrays to search for the value until there are no more arrays to be found. This way, you can search through arrays of arbitrary complexity instead of just two levels deep.
– jwueller
...
Best way to serialize an NSData into a hexadeximal string
...rsion.h
#import <Foundation/Foundation.h>
@interface NSData (NSData_Conversion)
#pragma mark - String Conversion
- (NSString *)hexadecimalString;
@end
NSData+Conversion.m
#import "NSData+Conversion.h"
@implementation NSData (NSData_Conversion)
#pragma mark - String Conversion
- (NSStr...
What is the use of the @ symbol in PHP?
...om error handler function with set_error_handler() then it will still get called, but this custom error handler can (and should) call error_reporting() which will return 0 when the call that triggered the error was preceded by an @...
...
How to access property of anonymous type in C#?
...null in three different situations!
o is null, so there is no object at all
o is non-null but doesn't have a property Foo
o has a property Foo but its real value happens to be null.
So this is not equivalent to the earlier examples, but may make sense if you want to treat all three cases the sa...