How do I convert all of the items in a list to floats? [duplicate]
[float(i) for i in lst] to be precise, it creates a new list with float values. Unlike the map approach it will work in py3k.
casting
Why don’t Java’s +=, -=, *=, /= compound assignment operators require casting long to int?
As always with these questions, the JLS holds the answer. In this case §15.26.2 Compound Assignment Operators. An extract: A compound assignment expression of the form E1 op= E2 is equivalent to E1 = (T)((E1) op (E2)), where T is the type of E1, except that E1 is evaluated only once. An example cited from §15.26.2 […] the following code is … Read more
Rails Migrations: tried to change the type of column from string to integer
I quote the manual about ALTER TABLE: A USING clause must be provided if there is no implicit or assignment cast from old to new type. What you need is: ALTER TABLE listings ALTER longitude TYPE integer USING longitude::int; ALTER TABLE listings ALTER latitude TYPE integer USING latitude::int; Or shorter and faster (for big tables) … Read more
How to cast simple pointer to a multidimensional-array of fixed size?
float (*somethingAsMatrix)[2] = (float (*)[2]) matrixReturnAsArray;
Why do we have reinterpret_cast in C++ when two chained static_cast can do its job?
There are things that reinterpret_cast can do that no sequence of static_casts can do (all from C++03 5.2.10): A pointer can be explicitly converted to any integral type large enough to hold it. A value of integral type or enumeration type can be explicitly converted to a pointer. A pointer to a function can be … Read more
Cast primitive type array into object array in java
Here is a simple one-liner: Double[] objects = ArrayUtils.toObject(primitives); You will need to import Apache commons-lang3: import org.apache.commons.lang3.ArrayUtils;
Laravel: how to set date format on model attribute casting?
After laravel 5.6, You can individually customize the format of Eloquent date and datetime casting: protected $casts = [ ‘birthday’ => ‘date:Y-m-d’, ‘joined_at’ => ‘datetime:Y-m-d H:00’, ]; This format is used when the model is serialized to an array or JSON data
Can I compare int with size_t directly in C?
It’s safe provided the int is zero or positive. If it’s negative, and size_t is of equal or higher rank than int, then the int will be converted to size_t and so its negative value will instead become a positive value. This new positive value is then compared to the size_t value, which may (in … Read more
What happens when I assign long int to int in C?
The language guarantees that int is at least 16 bits, long is at least 32 bits, and long can represent at least all the values that int can represent. If you assign a long value to an int object, it will be implicitly converted. There’s no need for an explicit cast; it would merely specify … Read more
User-defined conversion operator from base class
It’s not a design flaw. Here’s why: Entity entity = new Body(); Body body = (Body) entity; If you were allowed to write your own user-defined conversion here, there would be two valid conversions: an attempt to just do a normal cast (which is a reference conversion, preserving identity) and your user-defined conversion. Which should … Read more