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# ExAequoFn

Functional Tools and Helpers 

## Documentation

Functional helpers

### `const_fn` 

A function that returns a const

Ignoring up to 3 additional args, returning a const 

```elixir
    iex(1)> const_fn(1).()
    1
```

```elixir
    iex(2)> const_fn(2, 1)
    2
```

```elixir
    iex(3)> const_fn(:a, 1, 2)
    :a
```

```elixir
    iex(4)> const_fn(nil, 1, :a, [])
    nil
```

### `nil_fn`

Short for `const_fn(nil, ...)`
    
```elixir
    iex(5)> nil_fn()
    nil
```

```elixir
    iex(6)> nil_fn(42)
    nil
```

```elixir
    iex(7)> nil_fn({:a, :b}, "hello")
    nil
```

```elixir
    iex(8)> nil_fn([], "hello", %{})
    nil
```

 ### `tagged_fn`
 
 A function that wraps the result of `const_fn` into a tagged tuple

```elixir
    iex(9)> tagged_fn(:alpha).("beta")
    {:alpha, "beta"}
```

 ### `transform_many`
 
 delegates to `ExAequoFn.Transformer.many` (see below for details)



Implements functional transformation helpers

### `many`

`many` takes a list and a list of transsformers. A transformer is simply a function
that returns either `{:ok, value}` or `:error`

The list is traversed by calling all transformers on each element of the list until
the first transformer returns an `{:ok, value}` tuple in which case the element is
replaced by `value`. If a transformer returning an `:ok` value is found for **all**
elements, then the tuple `{:ok, [transformed values,...]}` is returned, otherwise
`:error` is returned

```elixir
    iex(1)> ft = %{a: 1, b: 2}
    ...(1)> st = %{a: 2, x: 3}
    ...(1)> ff = &Map.fetch(ft, &1)
    ...(1)> sf = &Map.fetch(st, &1)
    ...(1)> assert many([:a, :x], [ff, sf]) == {:ok, [1, 3]}
    ...(1)> assert many([:a, :z], [ff, sf]) == :error
```





## Author

Copyright © 2024 Robert Dober robert.dober@gmail.com

# LICENSE

GNU AFFERO GENERAL PUBLIC LICENSE Version 3, 19 November 2007 or later. Please refer to [LICENSE](LICENSE) for details.
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