216 lines
No EOL
5.1 KiB
Markdown
216 lines
No EOL
5.1 KiB
Markdown
# Builtin Functions
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## print
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Prints a string representation of the given variable to the standard output.
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```golang
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v := [1, 2, 3]
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print(v) // "[1, 2, 3]"
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print(1, 2, 3)
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// "1"
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// "2"
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// "3"
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```
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## printf
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Prints a formatted string to the standard output. It does not append the newline character at the end. The first argument must a String object. It's same as Go's `fmt.Printf`.
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```golang
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a := [1, 2, 3]
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printf("foo %v", a) // "foo [1, 2, 3]"
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```
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## sprintf
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Returns a formatted string. The first argument must be a String object. It's the same as Go's `fmt.Sprintf`.
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```golang
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a := [1, 2, 3]
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b := sprintp("foo %v", a) // b == "foo [1, 2, 3]"
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```
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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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## to_json
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Returns the JSON encoding of an object.
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```golang
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print(to_json([1, 2, 3])) // [1, 2, 3]
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print(to_json(4)) // 4
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print(to_json("five")) // "five"
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```
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## from_json
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Parses the JSON-encoded data and returns an object.
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```golang
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arr := from_json(`[1, 2, 3]`)
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four := from_json(`4`)
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five := from_json(`"five"`)
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```
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## string
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Tries to convert an object to string object. See [this](https://github.com/d5/tengo/wiki/Variable-Types) 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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## 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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## 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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## is_string
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Returns `true` if the object is string. Or it returns `false`.
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## is_int
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Returns `true` if the object is int. Or it returns `false`.
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## is_bool
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Returns `true` if the object is bool. Or it returns `false`.
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## is_float
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Returns `true` if the object is float. Or it returns `false`.
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## is_char
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Returns `true` if the object is char. Or it returns `false`.
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## is_bytes
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Returns `true` if the object is bytes. Or it returns `false`.
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## is_error
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Returns `true` if the object is error. Or it returns `false`.
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## is_undefined
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Returns `true` if the object is undefined. Or it returns `false`. |