Invalid type passed!
Received:
{type}
Expected one of:
{asideVariants.join(", ")}
: <>
{title &&
{title}
}
{children}
}
;
};
The Fift stack can contain values of the following types:
| Type | Description |
| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `Integer` | A TVM signed 257-bit integer. |
| `Cell` | A [TVM cell](/foundations/serialization/cells) for persistent data storage on TON Blockchain. A cell consists of up to `1023` data bits and up to `4` references to other cells. |
| `Slice` | A TVM slice is a read-only view of a TVM cell that allows sequential access to the cell's data and references. A cell can be converted into a slice, extracting stored bits and references without modifying the original cell. |
| `Builder` | A TVM builder is used to construct a cell by adding data and cell references. |
| `Null` | The TVM Null type has exactly one value `null`. In Fift, `null` is mostly used to initialize `Box`'es, hashmaps and lists. Usually denoted by `⊥`. |
| `Tuple` | A tuple is an ordered collection of values of any of the Fift types in this list, where each value is not necessarily of the same type. |
| `Continuation` | A [TVM continuation](/tvm/continuations) employed for execution of [TVM code](/tvm/instructions). |
| `String` | A UTF-8 string. |
| `Bytes` | An arbitrary sequence of 8-bit bytes, typically used to represent binary data. |
| `Box` | A container occupying one stack slot, that can be used to store one value of any type. Usually used to represent variables and mutable data structures. |
| `Atom` | A simple entity uniquely identified by its name. Can be used to represent identifiers, labels, operation names, tags, and stack markers. |
| `Object` | An arbitrary C++ object. Entities like word lists, execution tokens and Fift hashmaps are represented as having the type `Object`. This type may also be used by Fift extensions to manipulate other data types and interface with other C++ libraries. |
The first seven types listed above are shared with TVM. Others are Fift-specific.
## No boolean type
There is no dedicated `Boolean` type. Instead, booleans are represented as integers:
* "false" is `0`, "true" is `-1`, a 257-bit integer with all bits set to `1`.
* Logical operations are performed using bitwise operations.
* In conditional execution of blocks and loops with exit conditions, any nonzero integer in the conditions is regarded as "true".
## Tuples
Tuples can be used to represent values of arbitrary algebraic data types and Lisp-style lists. Refer to the Tuples section in the [basic values page](/languages/fift/basic-values#tuples).
## `Object` type
Many entities in Fift do not have a dedicated type, but they are assigned type `Object`. Fift provides words for creating and manipulating these entities.
Examples of entities of type `Object`:
* Word list: A partially created list of word references, used for creating an execution token. See section for blocks in the [control flow page](/languages/fift/control#blocks). See also [Section 4.7](/languages/fift/whitepaper#4-7-creating-and-manipulating-word-lists) in the whitepaper for a list of words that create and manipulate word lists.
* Execution token: Fift code that can be executed and manipulated on the Fift stack. See section for blocks in the [control flow page](/languages/fift/control#blocks) for more details.
* Fift hashmap: A hashmap specific for Fift. These hashmaps are not represented as cells, contrary to TVM hashmaps. As a comparison with TVM hashmaps, refer to [Section 6.3](/languages/fift/whitepaper#6-3-dictionary-manipulation) in the whitepaper for a list of words that create and manipulate TVM hashmaps.