https://github.com/bhgomes/subtypes.jl

Custom Subtyping in Julia
https://github.com/bhgomes/subtypes.jl

custom-types julia julia-language subtype subtypes typing

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Custom Subtyping in Julia

• Host: GitHub
• URL: https://github.com/bhgomes/subtypes.jl
• Owner: bhgomes
• License: unlicense
• Created: 2019-10-29T15:38:51.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2020-10-17T18:06:12.000Z (over 4 years ago)
• Last Synced: 2025-01-29T05:17:55.452Z (6 months ago)
• Topics: custom-types, julia, julia-language, subtype, subtypes, typing
• Language: Julia
• Homepage:
• Size: 39.1 KB
• Stars: 3
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Funding: .github/FUNDING.yml

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# SubTypes.jl

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_Custom Subtyping in Julia_



## Installation

To install, run the following in a Julia session:

```julia

]add SubTypes

```

## Custom Subtype

To create a custom subtype define the following data

```

SubType{T, P, Ctx}

        ^  ^  ^

        |  |  |

        |  |  L ______ Type Context

        |  L _________ Predicate Data

        L ____________ Underlying Type

```

and a predicate processing function

```julia

check_predicate(P, Val(Ctx), x::T)

```

which checks if `x::T` should be of type `SubType{T, P, Ctx}`. The context `Ctx` is the way to mark the subtypes for overloading.

## Predefined Custom Subtypes

The custom subtypes `Constrained` and `ConstrainedSymbol` are predefined in the `SubType` module. They emulate set inclusion subtyping, i.e.

```julia

x::Constrained{T, S}  <=>  x.value::T in S

```

The `ConstrainedSymbol` type emulates set inclusion for `Symbol` types. The `Constrained` type is defined as follows:

```julia

const Constrained{T,S} = SubType{T,S,:Constrained}

```

Inspiration for this type comes from [this post](https://discourse.julialang.org/t/creating-custom-type-of-enumerations-of-symbols/18635/7) by Mohamed Tarek [@mohamed82008](https://github.com/mohamed82008).

## Helper Functions

This module also comes with these helper functions defined for terms and types:

| Helper Function | Component | Description |

|-----------------|-----------|-------------|

| `eltype` | `SubType{T} => T` | The underlying type where the subtype terms are drawn from. |

| `predicate` | `SubType{T,P} => P` | The predicate data which determines the subtype terms. |

| `context` | `SubType{T,P,Ctx} => Ctx` | The implementation label for the `check_predicate` function. |

| `support` | `Constrained{T,S} => S` | The underlying set where the constrained variables are constrained to. |

---



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