site/contents/learn-extending.md
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content-type: "page"
title: "Learn: Extending min"
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{@ _defs_.md || 0 @}
min provides a fairly complete standard library with many useful modules. However, you may feel the need to extend min in order to perform more specialized tasks.
In such situations, you basically have the following options:
* Implementing new min modules using min itself
* Specifying your custom prelude program
* Embedding min in your [Nim](https://nim-lang.org) program
## Implementing new min modules using min itself
When you just want to create more high-level min operator using functionalities that are already available in min, the easiest way is to create your own reusable min modules.
The {#link-operator||lang||module#} (and the **+** sigil) allows you to create a new min module:
```
{
(dup *) :pow2
(dup dup * *) :pow3
(dup dup dup * * *) :pow4
} +quickpows
```
Save your code to a file (e.g. *quickpows.min*) and you can use it in other nim files using the {#link-operator||lang||load#} operator and the {#link-operator||lang||import#}:
```
'quickpows load
'quickpows import
2 pow3 pow2 puts ;prints 64
```
## Specifying your custom prelude program
By default, when min is started it loads the following *prelude.min* program:
```
; Imports
'str import
'io import
'logic import
'num import
'sys import
'stack import
'seq import
'dict import
'time import
'fs import
'lite? (
(
'crypto import
'math import
'net import
'http import
) ROOT with
) unless
; Unseal prompt symbol
'prompt unseal-symbol
```
Essentially, this causes min to import *all* the modules (except for some if the **lite** flag was defined at compilation time) and unseals the {#link-operator||lang||prompt#} symbol so that it can be customized. If you want, you can provide your own prelude file to specify your custom behaviors, selectively import modules, and define your own symbols, like this:
> %min-terminal%
> [$](class:prompt) min -i -p:myfile.min
## Embedding min in your Nim program
If you'd like to use min as a scripting language within your own program, and maybe extend it by implementing additional operators, you can use min as a Nim library.
To do so:
1. Install min sources using Nifty as explained in the {#link-page||download||Download#} section.
2. Import it in your Nim file.
3. Implement a new `proc` to define the module.
The following code is taken from [HastySite](https://github.com/h3rald/hastysite) and shows how to define a new `hastysite` module containing some symbols (`preprocess`, `postprocess`, `process-rules`, ...):
```
import min
proc hastysite_module*(i: In, hs1: HastySite) =
var hs = hs1
let def = i.define()
def.symbol("preprocess") do (i: In):
hs.preprocess()
def.symbol("postprocess") do (i: In):
hs.postprocess()
def.symbol("process-rules") do (i: In):
hs.interpret(hs.files.rules)
# ...
def.finalize("hastysite")
```
Then you need to:
4. Instantiate a new min interpreter using the `newMinInterpreter` proc.
5. Run the `proc` used to define the module.
6. Call the `interpret` method to interpret a min file or string:
```
proc interpret(hs: HastySite, file: string) =
var i = newMinInterpreter(file, file.parentDir)
i.hastysite_module(hs)
i.interpret(newFileStream(file, fmRead))
```
> %tip%
> Tip
>
> For more information on how to create new modules with Nim, have a look in the [lib folder](https://github.com/h3rald/min/tree/master/lib) of the min repository, which contains all the min modules included in the standard library.
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