> ## Documentation Index
> Fetch the complete documentation index at: https://voltaire.tevm.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# swapPosition()

> Get stack position swapped by SWAP opcode

<Card title="Try it Live" icon="play" href="https://playground.tevm.sh?example=primitives/opcode.ts">
  Run Opcode examples in the interactive playground
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## Opcode.swapPosition()

Get stack position swapped by SWAP opcode (1-16).

<Tabs>
  <Tab title="Functional API">
    ```typescript theme={null}
    import { swapPosition, SWAP1, SWAP16 } from 'tevm/Opcode'

    swapPosition(SWAP1)   // 1
    swapPosition(SWAP16)  // 16
    ```
  </Tab>
</Tabs>

## Parameters

* `opcode: BrandedOpcode` - Opcode to check

## Returns

`number | undefined` - Position (1-16) or undefined if not SWAP

## Stack Semantics

```
SWAP1:  [..., b, a] → [..., a, b]              (swap top 2)
SWAP2:  [..., c, b, a] → [..., a, b, c]        (swap top with 3rd)
SWAP16: [..., q, ..., a] → [..., a, ..., q]    (swap top with 17th)
```

## Related

* [isSwap()](/primitives/opcode/is-swap) - Check if SWAP opcode