Mu functions or 'recipes' are lists of instructions, one to a line. Each
instruction operates on some *ingredients* and returns some *products*.
```
[products] <- instruction [ingredients]
```
Result and ingredient *reagents* have to be variables. But you can have any
number of them. In particular you can have any number of products. For example,
you can perform integer division as follows:
```
quotient:number, remainder:number <- divide-with-remainder 11, 3
```
Each reagent can provide a name as well as its type separated by a colon. You
only have to specify the type the first time you mention a name, but you can
be more explicit if you choose. Types can be multiple words and even arbitrary
trees, like:
```nim
x:array:number:3 # x is an array of 3 numbers
y:list:number # y is a list of numbers
# without syntactic sugar
{z: (map (address array character) (list number))} # map from string to list of numbers
```
Try out the program now:
```shell
$ ./mu example1.mu
$
```
Not much to see yet, since it doesn't print anything. To print the result, try
adding the instruction `$print a` to the recipe.
---
Here's a second example, of a recipe that can take ingredients:
Recipes can specify headers showing their expected ingredients and products,
separated by `->` (unlike the `<-` in *calls*).
Since mu is a low-level VM language, it provides extra control at the cost of
verbosity. Using `local-scope`, you have explicit control over stack frames to
isolate your recipes (in a type-safe manner; more on that below). One
consequence: you have to explicitly `load-ingredients` after you set up the
stack.
An alternative syntax is what the above example is converted to internally:
The header gets dropped after checking types at call-sites, and after
replacing `load-ingredients` with explicit instructions to load each
ingredient separately, and to explicitly return products to the caller. After
this translation recipes are once again just lists of{
"ListenPort": 9001,
"StdoutLogging": true,
"LogFile": "getwtxt.log",
"DatabasePath": "getwtxt.db",
"DatabasePushInterval": "5m",
"StatusFetchInterval": "1h",
"Instance": {
"SiteName": "getwtxt",
"URL": "https://twtxt.example.com",
"OwnerName": "foo barrington",
"Email": "foo@barrington.ext",
"Description": "This is the twtxt registry for the tildeverse network of public unix servers."
}
}