Package byteorder provides functions for decoding and encoding little and big endian integer types from/to byte slices. Package big implements arbitrary-precision arithmetic (big numbers). The following numeric types are supported: The zero value for an Int, Rat, or Float correspond to 0. Thus, new values can be declared in the usual ways and denote 0 without further initialization: Alternatively, new values can be allocated and initialized with factory functions of the form: For instance, NewInt(x) returns an *Int set to the value of the int64 argument x, NewRat(a, b) returns a *Rat set to the fraction a/b where a and b are int64 values, and NewFloat(f) returns a *Float initialized to the float64 argument f. More flexibility is provided with explicit setters, for instance: Setters, numeric operations and predicates are represented as methods of the form: with T one of Int, Rat, or Float. For unary and binary operations, the result is the receiver (usually named z in that case; see below); if it is one of the operands x or y it may be safely overwritten (and its memory reused). Arithmetic expressions are typically written as a sequence of individual method calls, with each call corresponding to an operation. The receiver denotes the result and the method arguments are the operation's operands. For instance, given three *Int values a, b and c, the invocation computes the sum a + b and stores the result in c, overwriting whatever value was held in c before. Unless specified otherwise, operations permit aliasing of parameters, so it is perfectly ok to write to accumulate values x in a sum. (By always passing in a result value via the receiver, memory use can be much better controlled. Instead of having to allocate new memory for each result, an operation can reuse the space allocated for the result value, and overwrite that value with the new result in the process.) Notational convention: Incoming method parameters (including the receiver) are named consistently in the API to clarify their use. Incoming operands are usually named x, y, a, b, and so on, but never z. A parameter specifying the result is named z (typically the receiver). For instance, the arguments for (*Int).Add are named x and y, and because the receiver specifies the result destination, it is called z: Methods of this form typically return the incoming receiver as well, to enable simple call chaining. Methods which don't require a result value to be passed in (for instance, Int.Sign), simply return the result. In this case, the receiver is typically the first operand, named x: Various methods support conversions between strings and corresponding numeric values, and vice versa: *Int, *Rat, and *Float values implement the Stringer interface for a (default) string representation of the value, but also provide SetString methods to initialize a value from a string in a variety of supported formats (see the respective SetString documentation). Finally, *Int, *Rat, and *Float satisfy fmt.Scanner for scanning and (except for *Rat) the Formatter interface for formatted printing. This example demonstrates how to use big.Rat to compute the first 15 terms in the sequence of rational convergents for the constant e (base of natural logarithm). This example demonstrates how to use big.Int to compute the smallest Fibonacci number with 100 decimal digits and to test whether it is prime. This example shows how to use big.Float to compute the square root of 2 with a precision of 200 bits, and how to print the result as a decimal number.