tweag/nickel
1
1
Fork 0
mirror of https://github.com/tweag/nickel.git synced 2024-09-19 07:28:22 +03:00
Code Issues Projects Releases Wiki Activity
fb48c24cf3
nickel/examples/simple-contracts
History
Yann Hamdaoui c16fd3e1bd Add blameWith and fromPred, update examples accordingly
2021-11-23 15:31:35 +01:00
..
README.md Add blameWith and fromPred, update examples accordingly 2021-11-23 15:31:35 +01:00
simple-contract-bool.ncl Add blameWith and fromPred, update examples accordingly 2021-11-23 15:31:35 +01:00
simple-contract-div.ncl Put each example in its own directory with a README 2021-04-28 18:37:11 +02:00

README.md

Simple contracts

This directory contain two examples of simple contrtacts.

The first one, simple-contract-bool.ncl, defines simple contracts on booleans and illustrates their use as pre-conditions and post-conditions of a function.

The second one, 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 Lbl -> Dyn -> Dyn. However, they are just boolean predicates here. In this case, you should rather write them more succintly as predicates Dyn -> Bool and use contracts.fromPred 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.