casting – Page 44 – Tarik Billa

How to convert a factor to integer\numeric without loss of information?

September 9, 2022 by Tarik

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

Why use static_cast(x) instead of (int)x?

September 8, 2022 by Tarik

The main reason is that classic C casts make no distinction between what we call static_cast<>(), reinterpret_cast<>(), const_cast<>(), and dynamic_cast<>(). These four things are completely different. A static_cast<>() is usually safe. There is a valid conversion in the language, or an appropriate constructor that makes it possible. The only time it’s a bit risky is … Read more

Direct casting vs ‘as’ operator?

September 7, 2022 by Tarik

string s = (string)o; // 1 Throws InvalidCastException if o is not a string. Otherwise, assigns o to s, even if o is null. string s = o as string; // 2 Assigns null to s if o is not a string or if o is null. For this reason, you cannot use it with … Read more

How do I convert a string to a number in PHP?

September 7, 2022 by Tarik

You don’t typically need to do this, since PHP will coerce the type for you in most circumstances. For situations where you do want to explicitly convert the type, cast it: $num = “3.14”; $int = (int)$num; $float = (float)$num;

Change column type in pandas

August 29, 2022 by Tarik

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

How do I check if a string is a number (float)?

August 27, 2022 by Tarik

For non-negative (unsigned) integers only, use isdigit(): >>> a = “03523” >>> a.isdigit() True >>> b = “963spam” >>> b.isdigit() False Documentation for isdigit(): Python2, Python3 For Python 2 Unicode strings: isnumeric().

Regular cast vs. static_cast vs. dynamic_cast [duplicate]

August 27, 2022 by Tarik

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

Get int value from enum in C#

August 26, 2022 by Tarik

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

Do I cast the result of malloc?

August 24, 2022 by Tarik

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

When should static_cast, dynamic_cast, const_cast, and reinterpret_cast be used?

August 23, 2022 by Tarik

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