# Unsupported and reserved syntax

[Syntax and values](README.md)

These are features you may meet in other languages or in Pliro design plans. They are **not currently available Pliro syntax**. You do not need to learn them to start programming.

- **Type annotations** label a value's type in code, such as `let score: Number = 0`. A **return type**, such as `-> Number`, labels a function's result.
- `break` would end a loop early; `continue` would skip to its next turn; `pass` would stand for an empty instruction. `elif` means another conditional branch; `switch` and `match` select between cases.
- **Periodic timers** repeat at intervals. Pointer move/drag, GPIO changes, and sprite events would react to those actions. Only the [currently documented event forms](../guides/events.md) work.
- A **class** describes objects with data and behavior; a **method** is a function attached to an object; a **constructor** sets a new object up. **Inheritance** reuses another class's design. A separate **record type** would describe a fixed set of named fields.
- An **anonymous function**, or **lambda**, is a function without a declared name.
- **Async/await** and **tasks** are ways some languages describe work that can pause while other work continues. **Threads** are separate flows of execution; **channels** pass messages between them; **synchronization** coordinates their access to shared data. These syntax forms are unavailable; Pliro does have [cooperative event scripts](../concepts/event-loop.md).
- **Exceptions** let code report a failure for other code to handle. `try`, `catch`, `throw`, and `finally` are related forms in other languages.
- **Augmented assignment**, such as `+=`, combines a calculation and an update. **Increment/decrement** operators add or subtract one. Use Pliro's ordinary `set` instead.
- A **default parameter** has a preset value; a **named argument** is matched by label; an **optional parameter** may be omitted; a **variadic parameter** accepts a varying number of arguments; a **typed parameter** has a type label. User functions currently use a fixed number of positional arguments. Some built-ins have their own documented optional arguments.
- **String interpolation** inserts values into text using special placeholders. **Raw strings** would skip ordinary escape processing; **multiline strings** would span source lines. These forms and single-quoted text literals are unavailable.
- A **slice** selects a section of a list; a **comprehension** builds a list from a compact loop-like expression; a **range** describes a sequence such as the integers from one to ten. These shortcuts and looping directly over a Map are unavailable.
- **External packages** are reusable code from outside the project; an **import alias** gives an imported module another name. **Network dependency resolution** automatically finds and downloads required packages. Use the documented [project modules](../concepts/modules.md).
- A **date literal** would write a calendar date as its own value type. Date values and date input are unavailable.
- **Macros** and **compile-time metaprogramming** generate or change code while it is being built. **Conditional compilation** includes different code for different build conditions.

**Reserved** means a spelling is kept for a possible language use. Pliro recognizes `->` as a token but currently has no valid grammar rule using it. A design proposal is not a promise that a feature already works.

## Related entries

[Syntax and values](README.md) · [Built-ins](../builtins/README.md) · [Programming guides](../guides/README.md)