xgo/docs/builtins.md

Builtin Functions

print

Prints a string representation of the given variable to the standard output.

v := [1, 2, 3]
print(v)  // "[1, 2, 3]"

len

Returns the number of elements if the given variable is array, string, map, or module map.

v := [1, 2, 3]
l := len(v) // l == 3

copy

Creates a copy of the given variable. copy function calls Object.Copy interface method, which is expected to return a deep-copy of the value it holds.

v1 := [1, 2, 3]
v2 := v1
v3 := copy(v1)
v1[1] = 0
print(v2[1]) // "0"; 'v1' and 'v2' referencing the same array
print(v3[1]) // "2"; 'v3' not affected by 'v1'

append

Appends object(s) to an array (first argument) and returns a new array object. (Like Go's append builtin.) Currently, this function takes array type only.

v := [1]
v = append(v, 2, 3) // v == [1, 2, 3]

string

Tries to convert an object to string object. See this for more details on type conversion.

x := string(123) //  v == "123"

Optionally it can take the second argument, which will be returned if the first argument cannot be converted to string. Note that the second argument does not have to be string.

v = string(undefined, "foo")  // v == "foo"
v = string(undefined, false)  // v == false 

int

Tries to convert an object to int object. See this for more details on type conversion.

v := int("123") //  v == 123

Optionally it can take the second argument, which will be returned if the first argument cannot be converted to int. Note that the second argument does not have to be int.

v = int(undefined, 10)    // v == 10
v = int(undefined, false) // v == false 

bool

Tries to convert an object to bool object. See this for more details on type conversion.

v := bool(1) //  v == true

float

Tries to convert an object to float object. See this for more details on type conversion.

v := float("19.84") //  v == 19.84

Optionally it can take the second argument, which will be returned if the first argument cannot be converted to float. Note that the second argument does not have to be float.

v = float(undefined, 19.84)    // v == 19.84
v = float(undefined, false)    // v == false 

char

Tries to convert an object to char object. See this for more details on type conversion.

v := char(89) //  v == 'Y'

Optionally it can take the second argument, which will be returned if the first argument cannot be converted to float. Note that the second argument does not have to be float.

v = char(undefined, 'X')    // v == 'X'
v = char(undefined, false)  // v == false 

bytes

Tries to convert an object to bytes object. See this for more details on type conversion.

v := bytes("foo") //  v == [102 111 111]

Optionally it can take the second argument, which will be returned if the first argument cannot be converted to float. Note that the second argument does not have to be float.

v = bytes(undefined, bytes("foo"))    // v == bytes("foo")
v = bytes(undefined, false)           // v == false 

If you pass an int to bytes() function, it will create a new byte object with the given size.

v := bytes(100)

is_string

Returns true if the object is string. Or it returns false.

is_int

Returns true if the object is int. Or it returns false.

is_bool

Returns true if the object is bool. Or it returns false.

is_float

Returns true if the object is float. Or it returns false.

is_char

Returns true if the object is char. Or it returns false.

is_bytes

Returns true if the object is bytes. Or it returns false.

is_error

Returns true if the object is error. Or it returns false.

is_undefined

Returns true if the object is undefined. Or it returns false.