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What optimizations can GHC be expected to perform reliably?
...Right x
As an extended example, take this definition of last:
last [] = error "last: empty list"
last (x:[]) = x
last (x:x2:xs) = last (x2:xs)
We first transform it to
last_nil = error "last: empty list"
last_cons x [] = x
last_cons x (x2:xs) = last (x2:xs)
{-# INLINE last #-}
last [] = last_...
What is 'Pattern Matching' in functional languages?
...
head :: List a -> a
-- An empty list has no first item, so we raise an error.
head Nil = error "empty list"
-- If we are given a `Cons`, we only want the first part; that's the list's head.
head (Cons h _) = h
Since List a values can be of two different kinds, we need to handle each one...
How do I modify fields inside the new PostgreSQL JSON datatype?
...r the JSON object when the key is not used. If it's used, it will raise an error:
SELECT jsonb_insert('{"a":[null,{"b":[1]}]}', '{a,1,c}', jsonb '[2]')
-- will yield jsonb '{"a":[null,{"b":[1],"c":[2]}]}', but
SELECT jsonb_insert('{"a":[null,{"b":[1]}]}', '{a,1,b}', jsonb '[2]')
-- will raise SQLSTA...
How to sort two lists (which reference each other) in the exact same way
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I get an error running your example: TypeError: only integer arrays with one element can be converted to an index (Python 2.7.6, numpy 1.8.2). To fix it, list1 and list2 must be declared as numpy arrays.
– BenB
...
How to make a flat list out of list of lists?
...of the sum (if not given, 0 is used instead and this case will give you an error).
Because you are summing nested lists, you actually get [1,3]+[2,4] as a result of sum([[1,3],[2,4]],[]), which is equal to [1,3,2,4].
Note that only works on lists of lists. For lists of lists of lists, you'll need ...
Pairs from single list
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IndexError: pop from empty list
– HQuser
May 18 '19 at 11:48
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Swift Beta performance: sorting arrays
...level [-O].
Here is an in-place quicksort in Swift Beta:
func quicksort_swift(inout a:CInt[], start:Int, end:Int) {
if (end - start < 2){
return
}
var p = a[start + (end - start)/2]
var l = start
var r = end - 1
while (l <= r){
if (a[l] < p){
...
Check if a number is int or float
...
@David: issubclass would be an error, as it works on classes. isinstance checks if a given object is an instance of a class or one of that class's subclasses, so it's perfectly generic. Methinks that isinstance(obj, cls) is equivalent to issubclass(obj.__c...
How do I download a tarball from GitHub using cURL?
...temporary problem right now, but github is returning a 500 internal server error for this at the moment.
– B T
Oct 29 '13 at 21:15
15
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Convert json data to a html table [closed]
...uldHTMLTable
– xSx
Dec 17 '18 at 11:05
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