// Copyright 2011 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. /* Package builtin provides documentation for Go's built-in functions. The functions documented here are not actually in package builtin but their descriptions here allow godoc to present documentation for the language's special functions. */ package builtin // Type is here for the purposes of documentation only. It is a stand-in // for any Go type, but represents the same type for any given function // invocation. type Type int // IntegerType is here for the purposes of documentation only. It is a stand-in // for any integer type: int, uint, int8 etc. type IntegerType int // FloatType is here for the purposes of documentation only. It is a stand-in // for either float type: float32 or float64. type FloatType int // ComplexType is here for the purposes of documentation only. It is a // stand-in for either complex type: complex64 or complex128. type ComplexType int // The append built-in function appends elements to the end of a slice. If // it has sufficient capacity, the destination is resliced to accommodate the // new elements. If it does not, a new underlying array will be allocated. // Append returns the updated slice. It is therefore necessary to store the // result of append, often in the variable holding the slice itself: // slice = append(slice, elem1, elem2) // slice = append(slice, anotherSlice...) func append(slice []Type, elems ...Type) []Type // The copy built-in function copies elements from a source slice into a // destination slice. (As a special case, it also will copy bytes from a // string to a slice of bytes.) The source and destination may overlap. Copy // returns the number of elements copied, which will be the minimum of // len(src) and len(dst). func copy(dst, src []Type) int // The len built-in function returns the length of v, according to its type: // Array: the number of elements in v. // Pointer to array: the number of elements in *v (even if v is nil). // Slice, or map: the number of elements in v; if v is nil, len(v) is zero. // String: the number of bytes in v. // Channel: the number of elements queued (unread) in the channel buffer; // if v is nil, len(v) is zero. func len(v Type) int // The cap built-in function returns the capacity of v, according to its type: // Array: the number of elements in v (same as len(v)). // Pointer to array: the number of elements in *v (same as len(v)). // Slice: the maximum length the slice can reach when resliced; // if v is nil, cap(v) is zero. // Channel: the channel buffer capacity, in units of elements; // if v is nil, cap(v) is zero. func cap(v Type) int // The make built-in function allocates and initializes an object of type // slice, map, or chan (only). Like new, the first argument is a type, not a // value. Unlike new, make's return type is the same as the type of its // argument, not a pointer to it. The specification of the result depends on // the type: // Slice: The size specifies the length. The capacity of the slice is // equal to its length. A second integer argument may be provided to // specify a different capacity; it must be no smaller than the // length, so make([]int, 0, 10) allocates a slice of length 0 and // capacity 10. // Map: An initial allocation is made according to the size but the // resulting map has length 0. The size may be omitted, in which case // a small starting size is allocated. // Channel: The channel's buffer is initialized with the specified // buffer capacity. If zero, or the size is omitted, the channel is // unbuffered. func make(Type, size IntegerType) Type // The new built-in function allocates memory. The first argument is a type, // not a value, and the value returned is a pointer to a newly // allocated zero value of that type. func new(Type) *Type // The complex built-in function constructs a complex value from two // floating-point values. The real and imaginary parts must be of the same // size, either float32 or float64 (or assignable to them), and the return // value will be the corresponding complex type (complex64 for float32, // complex128 for float64). func complex(r, i FloatType) ComplexType // The real built-in function returns the real part of the complex number c. // The return value will be floating point type corresponding to the type of c. func real(c ComplexType) FloatType // The imaginary built-in function returns the imaginary part of the complex // number c. The return value will be floating point type corresponding to // the type of c. func imag(c ComplexType) FloatType // The close built-in function closes a channel, which must be either // bidirectional or send-only. It should be executed only by the sender, // never the receiver, and has the effect of shutting down the channel after // the last sent value is received. After the last value has been received // from a closed channel c, any receive from c will succeed without // blocking, returning the zero value for the channel element. The form // x, ok := <-c // will also set ok to false for a closed channel. func close(c chan<- Type) // The panic built-in function stops normal execution of the current // goroutine. When a function F calls panic, normal execution of F stops // immediately. Any functions whose execution was deferred by F are run in // the usual way, and then F returns to its caller. To the caller G, the // invocation of F then behaves like a call to panic, terminating G's // execution and running any deferred functions. This continues until all // functions in the executing goroutine have stopped, in reverse order. At // that point, the program is terminated and the error condition is reported, // including the value of the argument to panic. This termination sequence // is called panicking and can be controlled by the built-in function // recover. func panic(v interface{}) // The recover built-in function allows a program to manage behavior of a // panicking goroutine. Executing a call to recover inside a deferred // function (but not any function called by it) stops the panicking sequence // by restoring normal execution and retrieves the error value passed to the // call of panic. If recover is called outside the deferred function it will // not stop a panicking sequence. In this case, or when the goroutine is not // panicking, or if the argument supplied to panic was nil, recover returns // nil. Thus the return value from recover reports whether the goroutine is // panicking. func recover() interface{}