# \#contract **URL:** https://racket.discourse.group/tag/contract/27.md [Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md) --- ## [Question about unconstrained-domain-\> in the Racket guide](https://racket.discourse.group/t/question-about-unconstrained-domain-in-the-racket-guide/3786)
**Author:** [@chiroptical](https://racket.discourse.group/u/chiroptical)\ **Replies:** 10\ **Last updated:** [June 16, 2025, 7:58pm UTC](https://racket.discourse.group/t/question-about-unconstrained-domain-in-the-racket-guide/3786 "2025-06-16T19:58:52Z")
Hey! I am currently working my way through the Racket guide and I am struggling a bit to grok unconstrained-domain-\> in the example 7.3 Contracts on Functions in General. I'll paste the example here and work through my … --- ## [Exporting a struct invariant contract](https://racket.discourse.group/t/exporting-a-struct-invariant-contract/3694)
**Author:** [@KevinW](https://racket.discourse.group/u/KevinW)\ **Replies:** 2\ **Last updated:** [April 18, 2025, 10:23pm UTC](https://racket.discourse.group/t/exporting-a-struct-invariant-contract/3694 "2025-04-18T22:23:45Z")
Hi, I'm trying to create a struct with a contract that involves a relationship between two fields. The struct needs to be exported. It seems like what I need is an "invariant contract" as in struct/dc: 8.1 Data-structur… --- ## [How to attach contract on generic function?](https://racket.discourse.group/t/how-to-attach-contract-on-generic-function/3297)
**Author:** [@Andy](https://racket.discourse.group/u/Andy)\ **Replies:** 3\ **Last updated:** [November 6, 2024, 4:07pm UTC](https://racket.discourse.group/t/how-to-attach-contract-on-generic-function/3297 "2024-11-06T16:07:57Z")
Hello! I'm trying to use contract with generic functions. However, the code doesn't work as expected: #lang racket (require racket/generic) (define-generics g (g-func g)) (struct s () #:methods gen:g \[(define/cont… --- ## [Class contract on abstract method](https://racket.discourse.group/t/class-contract-on-abstract-method/2052)
**Author:** [@madkins23](https://racket.discourse.group/u/madkins23)\ **Replies:** 1\ **Last updated:** [June 28, 2023, 11:59pm UTC](https://racket.discourse.group/t/class-contract-on-abstract-method/2052 "2023-06-28T23:59:47Z")
In the following example code: #lang racket/base (require racket/class racket/contract) (define/contract parent% (class/c (override \[meth (-\>m string? void?)\])) (class object% (super-new) (abstract met… --- ## [Expressing contract conditions related to underlying data structures](https://racket.discourse.group/t/expressing-contract-conditions-related-to-underlying-data-structures/1707)
**Author:** [@Balrrach](https://racket.discourse.group/u/Balrrach)\ **Replies:** 0\ **Last updated:** [February 12, 2023, 5:41pm UTC](https://racket.discourse.group/t/expressing-contract-conditions-related-to-underlying-data-structures/1707 "2023-02-12T17:41:55Z")
Hello. I'm new to DbC and I'm trying to understand some of its fundamental concepts and how they could be applied to racket specifically. My questions is this: Suppose I want to define an interface. In order for the inte… --- ## [Advice on implementing a contract system?](https://racket.discourse.group/t/advice-on-implementing-a-contract-system/832)
**Author:** [@LiberalArtist](https://racket.discourse.group/u/LiberalArtist)\ **Replies:** 7\ **Last updated:** [April 3, 2022, 2:07pm UTC](https://racket.discourse.group/t/advice-on-implementing-a-contract-system/832 "2022-04-03T14:07:51Z")
I'm looking for advice on beginning the implementation of a contract system (i.e. not in Racket). I've been using and contributing to Guix, an unprivileged "purely functional" package manager (and full GNU/Linux distrib… --- ## [TIL: Enforcing contracts with \`contract-out\` from within an embedded test module](https://racket.discourse.group/t/til-enforcing-contracts-with-contract-out-from-within-an-embedded-test-module/525)
**Author:** [@sschwarzer](https://racket.discourse.group/u/sschwarzer)\ **Replies:** 1\ **Last updated:** [January 4, 2022, 10:40pm UTC](https://racket.discourse.group/t/til-enforcing-contracts-with-contract-out-from-within-an-embedded-test-module/525 "2022-01-04T22:40:28Z")
TL;DR :wink: It's possible to enforce and test contracts defined at the module boundary within a test module in the same file. Do this by require'ing (submod "..") in the test module: (module+ test (require ... … --- ## [Storing code for later evaluation at runtime](https://racket.discourse.group/t/storing-code-for-later-evaluation-at-runtime/485)
**Author:** [@rscho](https://racket.discourse.group/u/rscho)\ **Replies:** 2\ **Last updated:** [December 30, 2021, 5:51am UTC](https://racket.discourse.group/t/storing-code-for-later-evaluation-at-runtime/485 "2021-12-30T05:51:40Z")
Hi, I'm constructing a struct/dc contract through a macro. The real contract specs would only be known at struct instantiation time late into execution, and I need to store the original contract and modify it according… --- ## [Contract translation for use in an external system](https://racket.discourse.group/t/contract-translation-for-use-in-an-external-system/444)
**Author:** [@rscho](https://racket.discourse.group/u/rscho)\ **Replies:** 0\ **Last updated:** [December 19, 2021, 3:22pm UTC](https://racket.discourse.group/t/contract-translation-for-use-in-an-external-system/444 "2021-12-19T15:22:01Z")
Hi, I'd like to mirror Racket contracts on the SQLite side for a proof-of-concept dataframe library. Any type can be inserted in any column in SQLite, although types can optionally be enforced at runtime through trigger… --- ## [Best way to use contracts -- define/contract, contract-out, ...?](https://racket.discourse.group/t/best-way-to-use-contracts-define-contract-contract-out/247)
**Author:** [@dstorrs](https://racket.discourse.group/u/dstorrs)\ **Replies:** 12\ **Last updated:** [November 25, 2021, 11:47pm UTC](https://racket.discourse.group/t/best-way-to-use-contracts-define-contract-contract-out/247 "2021-11-25T23:47:01Z")
I make heavy use of define-contract in my code, since I like having the system do the work of catching when I pass the wrong thing from another function. I've seen other modules and documentation that leave the contract…