You have four main options for converting types in pandas: to_numeric() – provides functionality to safely convert non-numeric types (e.g. strings) to a suitable numeric type. (See also to_datetime() and to_timedelta().) astype() – convert (almost) any type to (almost) any other type (even if it’s not necessarily sensible to do so). Also allows you to … Read more
See the Warning section of ?factor: In particular, as.numeric applied to a factor is meaningless, and may happen by implicit coercion. To transform a factor f to approximately its original numeric values, as.numeric(levels(f))[f] is recommended and slightly more efficient than as.numeric(as.character(f)). The FAQ on R has similar advice. Why is as.numeric(levels(f))[f] more efficent than as.numeric(as.character(f))? … Read more
static_cast `static_cast` is used for cases where you basically want to reverse an implicit conversion, with a few restrictions and additions. `static_cast` performs no runtime checks. This should be used if you know that you refer to an object of a specific type, and thus a check would be unnecessary. Example: void func(void *data) { … Read more
Just cast the enum, e.g. int something = (int) Question.Role; The above will work for the vast majority of enums you see in the wild, as the default underlying type for an enum is int. However, as cecilphillip points out, enums can have different underlying types. If an enum is declared as a uint, long, … Read more
TL;DR int *sieve = (int *) malloc(sizeof(int) * length); has two problems. The cast and that you’re using the type instead of variable as argument for sizeof. Instead, do like this: int *sieve = malloc(sizeof *sieve * length); Long version No; you don’t cast the result, since: It is unnecessary, as void * is automatically … Read more
static_cast is the first cast you should attempt to use. It does things like implicit conversions between types (such as int to float, or pointer to void*), and it can also call explicit conversion functions (or implicit ones). In many cases, explicitly stating static_cast isn’t necessary, but it’s important to note that the T(something) syntax … Read more
How can I cast int to enum?
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
Since the pointer returned by malloc() is sufficiently well aligned to be used as a pointer to any type, you could (but probably shouldn’t) use: assert(sizeof(float) <= 10); void *data = malloc(10); char *str = data; strcpy(str, “123.4”); float *vp = data; *vp = strtof(str, NULL); …use *vp… free(data); And now you can use *vp … Read more
try this User user = new User(attrs.get(“mail”)!=null?attrs.get(“mail”).toString():null);