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aiken_design_patterns/merkelized_validator

Since transaction size is limited in Cardano, some scripts benefit from a solution which allows them to delegate parts of their validations. This becomes more prominent in cases where such validations can greatly benefit from optimization solutions that trade computation resources for script sizes (e.g. table lookups can take up more space so that costly computations can be averted).

This design pattern offers an interface for off-loading such validations into an external observer/withdrawal script, so that the sizes of the scripts themselves can stay within the limits of Cardano.

Be aware that total size of reference scripts is currently limited to 200KiB (204800 bytes), and they also impose additional fees in an exponential manner. See here and here for more info.

Types

ComputationRedeemer<a, b>

Datatype for redeemer of the “computation staking validator” to represent input argument(s) and output value(s).

As a simple example, a summation logic where it adds all its inputs together, can work with a redeemer of type ComputationRedeemer<List<Int>, Int>, and a valid redeemer data would be:

let valid_summation_io =
  ComputationRedeemer {
    input_arg: [1, 2, 3, 4, 5],
    result: 15,
  }

Constructors

  • ComputationRedeemer { input_arg: a, result: b }

ValidationRedeemer<a>

Datatype for a delegated validation. Compared to ComputationRedeemer, this datatype only carries input argument(s), and simply validates whether the computation passes.

Constructors

  • ValidationRedeemer { input_arg: a }

Functions 

delegated_compute(
  function_input: a,
  staking_validator: ScriptHash,
  redeemers: Pairs<ScriptPurpose, Redeemer>,
  redeemer_index: Int,
  input_data_coercer: fn(Data) -> a,
  output_data_coercer: fn(Data) -> b,
) -> b

Given an arbitrary Data as input, this function expects to find a Withdraw script purpose in redeemers for staking_validator, with a redeemer of type ValidationRedeemer<Data, Data>, which will be coerced into your custom datatypes using your provided Data validators (input_data_coercer and output_data_coercer).

delegated_validation(
  function_input: a,
  staking_validator: ScriptHash,
  redeemers: Pairs<ScriptPurpose, Redeemer>,
  redeemer_index: Int,
  input_data_coercer: fn(Data) -> a,
) -> Bool

Similar to delegated_compute, with the difference that no values are expected to be returned by the staking script.

computation_withdrawal_wrapper(
  redeemer: ComputationRedeemer<a, b>,
  function: fn(a) -> b,
) -> Bool

Helper function for defining your “computation stake validator.” The resulting stake validator will carry out the provided function’s logic, and redeemer must contain the input(s) and expected output(s).

validation_withdrawal_wrapper(
  redeemer: ValidationRedeemer<a>,
  validation: fn(a) -> Bool,
) -> Bool

Helper function for defining your delegated validation. The resulting stake validator will carry out the provided validation’s logic with given input(s) through its redeemer.

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