Source File
builtin.go
Belonging Package
builtin
// 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 predeclared identifiers.The items documented here are not actually in package builtinbut their descriptions here allow godoc to present documentationfor the language's special identifiers.*/package builtinimport// bool is the set of boolean values, true and false.type bool bool// true and false are the two untyped boolean values.const (true = 0 == 0 // Untyped bool.false = 0 != 0 // Untyped bool.)// uint8 is the set of all unsigned 8-bit integers.// Range: 0 through 255.type uint8 uint8// uint16 is the set of all unsigned 16-bit integers.// Range: 0 through 65535.type uint16 uint16// uint32 is the set of all unsigned 32-bit integers.// Range: 0 through 4294967295.type uint32 uint32// uint64 is the set of all unsigned 64-bit integers.// Range: 0 through 18446744073709551615.type uint64 uint64// int8 is the set of all signed 8-bit integers.// Range: -128 through 127.type int8 int8// int16 is the set of all signed 16-bit integers.// Range: -32768 through 32767.type int16 int16// int32 is the set of all signed 32-bit integers.// Range: -2147483648 through 2147483647.type int32 int32// int64 is the set of all signed 64-bit integers.// Range: -9223372036854775808 through 9223372036854775807.type int64 int64// float32 is the set of all IEEE 754 32-bit floating-point numbers.type float32 float32// float64 is the set of all IEEE 754 64-bit floating-point numbers.type float64 float64// complex64 is the set of all complex numbers with float32 real and// imaginary parts.type complex64 complex64// complex128 is the set of all complex numbers with float64 real and// imaginary parts.type complex128 complex128// string is the set of all strings of 8-bit bytes, conventionally but not// necessarily representing UTF-8-encoded text. A string may be empty, but// not nil. Values of string type are immutable.type string string// int is a signed integer type that is at least 32 bits in size. It is a// distinct type, however, and not an alias for, say, int32.type int int// uint is an unsigned integer type that is at least 32 bits in size. It is a// distinct type, however, and not an alias for, say, uint32.type uint uint// uintptr is an integer type that is large enough to hold the bit pattern of// any pointer.type uintptr uintptr// byte is an alias for uint8 and is equivalent to uint8 in all ways. It is// used, by convention, to distinguish byte values from 8-bit unsigned// integer values.type byte = uint8// rune is an alias for int32 and is equivalent to int32 in all ways. It is// used, by convention, to distinguish character values from integer values.type rune = int32// any is an alias for interface{} and is equivalent to interface{} in all ways.type any = interface{}// comparable is an interface that is implemented by all comparable types// (booleans, numbers, strings, pointers, channels, arrays of comparable types,// structs whose fields are all comparable types).// The comparable interface may only be used as a type parameter constraint,// not as the type of a variable.type comparable interface{ comparable }// iota is a predeclared identifier representing the untyped integer ordinal// number of the current const specification in a (usually parenthesized)// const declaration. It is zero-indexed.const iota = 0 // Untyped int.// nil is a predeclared identifier representing the zero value for a// pointer, channel, func, interface, map, or slice type.var nil Type // Type must be a pointer, channel, func, interface, map, or slice type// 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// Type1 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 Type1 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 float32// ComplexType is here for the purposes of documentation only. It is a// stand-in for either complex type: complex64 or complex128.type ComplexType complex64// 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...)//// As a special case, it is legal to append a string to a byte slice, like this://// slice = append([]byte("hello "), "world"...)func append( []Type, ...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(, []Type) int// The delete built-in function deletes the element with the specified key// (m[key]) from the map. If m is nil or there is no such element, delete// is a no-op.func delete( map[Type]Type1, Type)// 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.//// For some arguments, such as a string literal or a simple array expression, the// result can be a constant. See the Go language specification's "Length and// capacity" section for details.func len( 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.//// For some arguments, such as a simple array expression, the result can be a// constant. See the Go language specification's "Length and capacity" section for// details.func cap( 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. For example, make([]int, 0, 10) allocates an underlying array// of size 10 and returns a slice of length 0 and capacity 10 that is// backed by this underlying array.// - Map: An empty map is allocated with enough space to hold the// specified number of elements. 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, ...IntegerType) Type// The max built-in function returns the largest value of a fixed number of// arguments of [cmp.Ordered] types. There must be at least one argument.// If T is a floating-point type and any of the arguments are NaNs,// max will return NaN.func max[ cmp.Ordered]( , ...)// The min built-in function returns the smallest value of a fixed number of// arguments of [cmp.Ordered] types. There must be at least one argument.// If T is a floating-point type and any of the arguments are NaNs,// min will return NaN.func min[ cmp.Ordered]( , ...)// 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(, 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( ComplexType) FloatType// The imag 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( ComplexType) FloatType// The clear built-in function clears maps and slices.// For maps, clear deletes all entries, resulting in an empty map.// For slices, clear sets all elements up to the length of the slice// to the zero value of the respective element type. If the argument// type is a type parameter, the type parameter's type set must// contain only map or slice types, and clear performs the operation// implied by the type argument. If t is nil, clear is a no-op.func clear[ ~[]Type | ~map[Type]Type1]( )// 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 and empty channel.func close( 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 with a non-zero exit code. This// termination sequence is called panicking and can be controlled by the// built-in function recover.//// Starting in Go 1.21, calling panic with a nil interface value or an// untyped nil causes a run-time error (a different panic).// The GODEBUG setting panicnil=1 disables the run-time error.func panic( any)// 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, recover returns nil.//// Prior to Go 1.21, recover would also return nil if panic is called with// a nil argument. See [panic] for details.func recover() any// The print built-in function formats its arguments in an// implementation-specific way and writes the result to standard error.// Print is useful for bootstrapping and debugging; it is not guaranteed// to stay in the language.func print( ...Type)// The println built-in function formats its arguments in an// implementation-specific way and writes the result to standard error.// Spaces are always added between arguments and a newline is appended.// Println is useful for bootstrapping and debugging; it is not guaranteed// to stay in the language.func println( ...Type)// The error built-in interface type is the conventional interface for// representing an error condition, with the nil value representing no error.type error interface {Error() string}
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