builtin

func close

1func close(c chan<- Type)

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 print

1func print(args ...Type)

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 println

1func println(args ...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 make

1func make(t Type, size ...IntegerType) Type

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 new

1func new(Type) *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 len

1func len(v 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.

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.