---
id: haskell
title: Haskell
sidebar_label: Haskell
---

## What

Display the currently active Glasgow [Haskell][haskell] Compiler (GHC) version.

## Sample Configuration

import Config from "@site/src/components/Config.js";

<Config
  data={{
    type: "haskell",
    style: "powerline",
    powerline_symbol: "\uE0B0",
    foreground: "#906cff",
    background: "#100e23",
    template: " \ue61f {{ .Full }}",
  }}
/>

## Options

| Name                   |    Type    |                             Default                             | Description                                                                                                                                                                                                                                                                                    |
| ---------------------- | :--------: | :-------------------------------------------------------------: | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `home_enabled`         | `boolean`  |                             `false`                             | display the segment in the HOME folder or not                                                                                                                                                                                                                                                  |
| `fetch_version`        | `boolean`  |                             `true`                              | fetch the GHC version                                                                                                                                                                                                                                                                          |
| `cache_duration`       |  `string`  |                             `none`                              | the duration for which the version will be cached. The duration is a string in the format `1h2m3s` and is parsed using the [time.ParseDuration] function from the Go standard library. To disable the cache, use `none`                                                                        |
| `missing_command_text` |  `string`  |                                                                 | text to display when the command is missing                                                                                                                                                                                                                                                    |
| `display_mode`         |  `string`  |                            `context`                            | <ul><li>`always`: the segment is always displayed</li><li>`files`: the segment is only displayed when file `extensions` listed are present</li><li>`context`: displays the segment when the environment or files is active</li></ul>                                                           |
| `version_url_template` |  `string`  |                                                                 | a go [text/template][go-text-template] [template][templates] that creates the URL of the version info / release notes                                                                                                                                                                          |
| `stack_ghc_mode`       |  `string`  |                             `never`                             | determines when to use `stack ghc` to retrieve the version information. Using `stack ghc` will decrease performance.<ul><li>`never`: never use `stack ghc`</li><li>`package`: only use `stack ghc` when `stack.yaml` is in the root of the </li><li>`always`: always use `stack ghc`</li></ul> |
| `extensions`           | `[]string` | `*.hs, *.lhs, stack.yaml, package.yaml, *.cabal, cabal.project` | allows to override the default list of file extensions to validate                                                                                                                                                                                                                             |
| `folders`              | `[]string` |                                                                 | allows to override the list of folder names to validate                                                                                                                                                                                                                                        |
| `tooling`              | `[]string` |                              `ghc`                              | the tooling to use for fetching the version. Available options: `ghc`, `stack`                                                                                                                                                                                                                 |

## Template ([info][templates])

:::note default template

```template
{{ if .Error }}{{ .Error }}{{ else }}{{ .Full }}{{ end }}
```

:::

### Properties

| Name        | Type      | Description                                        |
| ----------- | --------- | -------------------------------------------------- |
| `.Full`     | `string`  | the full version                                   |
| `.Major`    | `string`  | major number                                       |
| `.Minor`    | `string`  | minor number                                       |
| `.Patch`    | `string`  | patch number                                       |
| `.URL`      | `string`  | URL of the version info / release notes            |
| `.Error`    | `string`  | error encountered when fetching the version string |
| `.StackGhc` | `boolean` | `true` if `stack ghc` was used, otherwise `false`  |

[go-text-template]: https://golang.org/pkg/text/template/
[templates]: /docs/configuration/templates
[haskell]: https://www.haskell.org/
[time.ParseDuration]: https://golang.org/pkg/time/#ParseDuration
