# `MPP.Hex`
[🔗](https://github.com/ZenHive/mpp/blob/v0.10.0/lib/mpp/hex.ex#L1)

Small internal hex-string helpers shared across the payment-method and
wire-format modules.

These cover two string-level checks that are used before length/format
validation of Ethereum-style hex addresses and calldata:

  * `strip_0x/1` — drop an optional `0x` prefix, returning the rest unchanged.
  * `hex_string?/1` — true when the (already prefix-stripped) string is one or
    more bare hex digits, with **no** `0x` prefix.

For decode/encode/integer conversion use `Onchain.Hex` (`decode/1`, `encode/1`,
`to_integer/1`, `valid?/1`). Note `Onchain.Hex.valid?/1` accepts a `0x` prefix,
whereas `hex_string?/1` here does not — they are not interchangeable.

# `hex_string?`

```elixir
@spec hex_string?(String.t()) :: boolean()
```

Return true when `str` is one or more bare hex digits (`0-9a-fA-F`), with no
`0x` prefix. An empty string is not valid hex.

# `strip_0x`

```elixir
@spec strip_0x(String.t()) :: String.t()
```

Drop an optional leading `0x` prefix, returning the remaining string unchanged.

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*Consult [api-reference.md](api-reference.md) for complete listing*