200 lines
5.2 KiB
Markdown
200 lines
5.2 KiB
Markdown
# Builtin Functions
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## len
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Returns the number of elements if the given variable is array, string, map, or module map.
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```golang
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v := [1, 2, 3]
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l := len(v) // l == 3
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```
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## copy
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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.
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```golang
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v1 := [1, 2, 3]
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v2 := v1
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v3 := copy(v1)
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v1[1] = 0
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print(v2[1]) // "0"; 'v1' and 'v2' referencing the same array
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print(v3[1]) // "2"; 'v3' not affected by 'v1'
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```
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## append
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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.
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```golang
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v := [1]
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v = append(v, 2, 3) // v == [1, 2, 3]
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```
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## type_name
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Returns the type_name of an object.
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```golang
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type_name(1) // int
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type_name("str") // string
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type_name([1, 2, 3]) // array
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```
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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.
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```golang
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v = string(undefined, "foo") // v == "foo"
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v = string(undefined, false) // v == false
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```
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## string
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Tries to convert an object to string object. See [Runtime Types](https://github.com/d5/tengo/blob/master/docs/runtime-types.md) for more details on type conversion.
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```golang
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x := string(123) // v == "123"
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```
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## int
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Tries to convert an object to int object. See [this](https://github.com/d5/tengo/blob/master/docs/runtime-types.md) for more details on type conversion.
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```golang
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v := int("123") // v == 123
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```
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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.
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```golang
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v = int(undefined, 10) // v == 10
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v = int(undefined, false) // v == false
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```
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## bool
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Tries to convert an object to bool object. See [this](https://github.com/d5/tengo/blob/master/docs/runtime-types.md) for more details on type conversion.
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```golang
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v := bool(1) // v == true
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```
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## float
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Tries to convert an object to float object. See [this](https://github.com/d5/tengo/blob/master/docs/runtime-types.md) for more details on type conversion.
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```golang
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v := float("19.84") // v == 19.84
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```
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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.
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```golang
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v = float(undefined, 19.84) // v == 19.84
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v = float(undefined, false) // v == false
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```
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## char
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Tries to convert an object to char object. See [this](https://github.com/d5/tengo/blob/master/docs/runtime-types.md) for more details on type conversion.
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```golang
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v := char(89) // v == 'Y'
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```
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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.
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```golang
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v = char(undefined, 'X') // v == 'X'
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v = char(undefined, false) // v == false
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```
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## bytes
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Tries to convert an object to bytes object. See [this](https://github.com/d5/tengo/blob/master/docs/runtime-types.md) for more details on type conversion.
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```golang
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v := bytes("foo") // v == [102 111 111]
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```
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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.
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```golang
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v = bytes(undefined, bytes("foo")) // v == bytes("foo")
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v = bytes(undefined, false) // v == false
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```
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If you pass an int to `bytes()` function, it will create a new byte object with the given size.
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```golang
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v := bytes(100)
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```
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## time
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Tries to convert an object to time value.
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```golang
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v := time(1257894000) // 2009-11-10 23:00:00 +0000 UTC
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```
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## is_string
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Returns `true` if the object's type is string. Or it returns `false`.
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## is_int
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Returns `true` if the object's type is int. Or it returns `false`.
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## is_bool
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Returns `true` if the object's type is bool. Or it returns `false`.
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## is_float
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Returns `true` if the object's type is float. Or it returns `false`.
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## is_char
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Returns `true` if the object's type is char. Or it returns `false`.
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## is_bytes
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Returns `true` if the object's type is bytes. Or it returns `false`.
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## is_error
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Returns `true` if the object's type is error. Or it returns `false`.
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## is_undefined
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Returns `true` if the object's type is undefined. Or it returns `false`.
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## is_function
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Returns `true` if the object's type is function or closure. Or it returns `false`. Note that `is_function` returns `false` for builtin functions and user-provided callable objects.
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## is_callable
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Returns `true` if the object is callable (e.g. function, closure, builtin function, or user-provided callable objects). Or it returns `false`.
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## is_array
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Returns `true` if the object's type is array. Or it returns `false`.
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## is_immutable_array
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Returns `true` if the object's type is immutable array. Or it returns `false`.
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## is_map
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Returns `true` if the object's type is map. Or it returns `false`.
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## is_immutable_map
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Returns `true` if the object's type is immutable map. Or it returns `false`.
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## is_time
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Returns `true` if the object's type is time. Or it returns `false`.
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