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nickel/examples/simple-contracts
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Yann Hamdaoui 7938c0bb69
Add topiary to pre-commit-hooks (#1391) 
* Add Nickel formatting to pre-commit-hooks/CI

* Run topiary on examples

* Topiary formatter on stdlib

* Add exclude list for Nickel formatting

* Reformat internals.ncl after rebase
2023-06-22 09:41:50 +00:00
..
README.md Pass on examples + code formatting (#1261) 2023-04-18 13:24:49 +00:00
simple-contract-bool.ncl Add topiary to pre-commit-hooks (#1391) 2023-06-22 09:41:50 +00:00
simple-contract-div.ncl Add topiary to pre-commit-hooks (#1391) 2023-06-22 09:41:50 +00:00

README.md

Simple contracts

This directory contains two examples of simple contracts.

  • simple-contract-bool.ncl defines simple contracts on booleans and illustrates the use of contracts as pre-conditions and post-conditions of a function.
  • simple-contract-div.ncl, defines simple contracts on numbers and illustrates the application of several contracts to one value. It is expected to fail, to demonstrate basic error-reporting for contracts.

For illustrative purpose, those contracts are written as plain custom contracts: functions Label -> Dyn -> Dyn. However, they are just boolean predicates here. In this case, you should rather write them more succinctly as predicates Dyn -> Bool and use std.contract.from_predicate to obtain the corresponding contracts.

Run

nickel -f simple-contract-bool.ncl
nickel -f simple-contract-div.ncl

Playground

You can try to break the one of the contracts of simple-contract-bool.ncl to see them fail. Conversely, you can provide a valid value in simple-contract-div.ncl to see the execution succeed.