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# Tengo Runtime Types
- **Int**: signed 64bit integer
- **String**: string
- **Float**: 64bit floating point
- **Bool**: boolean
- **Char**: character (`rune` in Go)
- **Bytes**: byte array (`[]byte` in Go)
- **Array**: objects array (`[]Object` in Go)
- **ImmutableArray**: immutable object array (`[]Object` in Go)
- **Map**: objects map with string keys (`map[string]Object` in Go)
- **ImmutableMap**: immutable object map with string keys (`map[string]Object`
in Go)
- **Time**: time (`time.Time` in Go)
- **Error**: an error with underlying Object value of any type
- **Undefined**: undefined
## Type Conversion/Coercion Table
|src\dst |Int |String |Float |Bool |Char |Bytes |Array |Map |Time |Error |Undefined|
| :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: |
|Int | - |_strconv_ |float64(v)|!IsFalsy()| rune(v)|**X**|**X**|**X**|_time.Unix()_|**X**|**X**|
|String |_strconv_| - |_strconv_|!IsFalsy()|**X**|[]byte(s)|**X**|**X**|**X**|**X**|**X**|
|Float |int64(f) |_strconv_ | - |!IsFalsy()|**X**|**X**|**X**|**X**|**X**|**X**|**X**|
|Bool |1 / 0 |"true" / "false"|**X** | - |**X**|**X**|**X**|**X**|**X**|**X**|**X**|
|Char |int64(c) |string(c) |**X** |!IsFalsy()| - |**X**|**X**|**X**|**X**|**X**|**X**|
|Bytes |**X** |string(y)|**X** |!IsFalsy()|**X**| - |**X**|**X**|**X**|**X**|**X**|
|Array |**X** |"[...]" |**X** |!IsFalsy()|**X**|**X**| - |**X**|**X**|**X**|**X**|
|Map |**X** |"{...}" |**X** |!IsFalsy()|**X**|**X**|**X**| - |**X**|**X**|**X**|
|Time |**X** |String() |**X** |!IsFalsy()|**X**|**X**|**X**|**X**| - |**X**|**X**|
|Error |**X** |"error: ..." |**X** |false|**X**|**X**|**X**|**X**|**X**| - |**X**|
|Undefined|**X** |**X**|**X** |false|**X**|**X**|**X**|**X**|**X**|**X**| - |
_* **X**: No conversion; Typed value functions for `Variable` will
return zero values._
_* strconv: converted using Go's conversion functions from `strconv` package._
_* IsFalsy(): use [Object.IsFalsy()](#objectisfalsy) function_
_* String(): use `Object.String()` function_
_* time.Unix(): use `time.Unix(v, 0)` to convert to Time_
## Object.IsFalsy()
`Object.IsFalsy()` interface method is used to determine if a given value
should evaluate to `false` (e.g. for condition expression of `if` statement).
- **Int**: `n == 0`
- **String**: `len(s) == 0`
- **Float**: `isNaN(f)`
- **Bool**: `!b`
- **Char**: `c == 0`
- **Bytes**: `len(bytes) == 0`
- **Array**: `len(arr) == 0`
- **Map**: `len(map) == 0`
- **Time**: `Time.IsZero()`
- **Error**: `true` _(Error is always falsy)_
- **Undefined**: `true` _(Undefined is always falsy)_
## Type Conversion Builtin Functions
- `string(x)`: tries to convert `x` into string; returns `undefined` if failed
- `int(x)`: tries to convert `x` into int; returns `undefined` if failed
- `bool(x)`: tries to convert `x` into bool; returns `undefined` if failed
- `float(x)`: tries to convert `x` into float; returns `undefined` if failed
- `char(x)`: tries to convert `x` into char; returns `undefined` if failed
- `bytes(x)`: tries to convert `x` into bytes; returns `undefined` if failed
- `bytes(N)`: as a special case this will create a Bytes variable with the
given size `N` (only if `N` is int)
- `time(x)`: tries to convert `x` into time; returns `undefined` if failed
- See [Builtins](https://github.com/d5/tengo/blob/master/docs/builtins.md) for
the full list of builtin functions.
## Type Checking Builtin Functions
- `is_string(x)`: returns `true` if `x` is string; `false` otherwise
- `is_int(x)`: returns `true` if `x` is int; `false` otherwise
- `is_bool(x)`: returns `true` if `x` is bool; `false` otherwise
- `is_float(x)`: returns `true` if `x` is float; `false` otherwise
- `is_char(x)`: returns `true` if `x` is char; `false` otherwise
- `is_bytes(x)`: returns `true` if `x` is bytes; `false` otherwise
- `is_array(x)`: return `true` if `x` is array; `false` otherwise
- `is_immutable_array(x)`: return `true` if `x` is immutable array; `false`
otherwise
- `is_map(x)`: return `true` if `x` is map; `false` otherwise
- `is_immutable_map(x)`: return `true` if `x` is immutable map; `false`
otherwise
- `is_time(x)`: return `true` if `x` is time; `false` otherwise
- `is_error(x)`: returns `true` if `x` is error; `false` otherwise
- `is_undefined(x)`: returns `true` if `x` is undefined; `false` otherwise
- See [Builtins](https://github.com/d5/tengo/blob/master/docs/builtins.md) for
the full list of builtin functions.
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