phi 0.4.1

Phi is a library for fluent functional programming in Python which includes a DSL + facilities to create libraries that integrate with it.

# Phi
Phi library for [fluent](https://en.wikipedia.org/wiki/Fluent_interface) functional programming in Python that intends to remove as much of the pain as possible from your functional programming experience in Python by providing the following modules

* [dsl](https://cgarciae.github.io/phi/dsl.m.html): a small DSL that helps you compose computations in various ways & more.
* [lambdas](https://cgarciae.github.io/phi/lambdas.m.html): easy way to create quick lambdas with a mathematical flavor.
* [builder](https://cgarciae.github.io/phi/builder.m.html): an extensible class that enables you to integrate other libraries into the DSL as a fluent API, to do it lets you [register](https://cgarciae.github.io/phi/builder.m.html#phi.builder.Builder.RegisterMethod) functions as methods or even [patch](https://cgarciae.github.io/phi/builder.m.html#phi.builder.Builder.PatchAt) an entire module with a few lines of code.

### Libraries
Phi currently powers the following libraries:

* [PythonBuilder](https://cgarciae.github.io/phi/python_builder.m.html) : helps you integrate Python's built-in functions and keywords into the phi DSL and it also includes a bunch of useful helpers for common stuff. `phi`'s global `P` object is an instance of this class. [Shipped with Phi]
* [TensorBuilder](https://github.com/cgarciae/tensorbuilder): a TensorFlow library enables you to easily create complex deep neural networks by leveraging the phi DSL to help define their structure.
* NumpyBuilder: Comming soon!

## Documentation
Check out the [complete documentation](https://cgarciae.github.io/phi/).

## Getting Started
The global `phi.P` object exposes most of the API and preferably should be imported directly. The most simple thing the DSL does is function composition:

```python
from phi import P

def add1(x): return x + 1
def mul3(x): return x * 3

x = P.Pipe(
1.0, #input 1
add1, #1 + 1 == 2
mul3 #2 * 3 == 6
)

assert x == 6
```

Use phi [lambdas](https://cgarciae.github.io/phi/lambdas.m.html) to create the functions

```python
from phi import P

x = P.Pipe(
1.0, #input 1
P + 1, #1 + 1 == 2
P * 3 #2 * 3 == 6
)

assert x == 6
```

Create a branched computation instead

```python
from phi import P

[x, y] = P.Pipe(
1.0, #input 1
[
P + 1 #1 + 1 == 2
,
P * 3 #1 * 3 == 3
]
)

assert x == 2
assert y == 3
```

Compose it with a function equivalent to `f(x) = (x + 3) / (x + 1)`

```python
from phi import P

[x, y] = P.Pipe(
1.0, #input 1
(P + 3) / (P + 1), #(1 + 3) / (1 + 1) == 4 / 2 == 2
[
P + 1 #2 + 1 == 3
,
P * 3 #2 * 3 == 6
]
)

assert x == 3
assert y == 6
```

Give names to the branches

```python
from phi import P

result = P.Pipe(
1.0, #input 1
(P + 3) / (P + 1), #(1 + 3) / (1 + 1) == 4 / 2 == 2
dict(
x = P + 1 #2 + 1 == 3
,
y = P * 3 #2 * 3 == 6
)
)

assert result.x == 3
assert result.y == 6
```

Divide the `x` by the `y`.

```python
from phi import P, Rec

result = P.Pipe(
1.0, #input 1
(P + 3) / (P + 1), #(1 + 3) / (1 + 1) == 4 / 2 == 2
dict(
x = P + 1 #2 + 1 == 3
,
y = P * 3 #2 * 3 == 6
),
Rec.x / Rec.y #3 / 6 == 0.5
)

assert result == 0.5
```

Save the value from the `(P + 3) / (P + 1)` computation as `s` and load it at the end in a branch

```python
from phi import P, Rec

[result, s] = P.Pipe(
1.0, #input 1
(P + 3) / (P + 1), {'s'}, #4 / 2 == 2, saved as 's'
dict(
x = P + 1 #2 + 1 == 3
,
y = P * 3 #2 * 3 == 6
),
[
Rec.x / Rec.y #3 / 6 == 0.5
,
's' #load 's' == 2
]
)

assert result == 0.5
assert s == 2
```

Add 3 to the loaded `s` for fun and profit

```python
from phi import P, Rec, Read

[result, s] = P.Pipe(
1.0, #input 1
(P + 3) / (P + 1), {'s'}, #4 / 2 == 2, saved as 's'
dict(
x = P + 1 #2 + 1 == 3
,
y = P * 3 #2 * 3 == 6
),
[
Rec.x / Rec.y #3 / 6 == 0.5
,
Read.s + 3 # 2 + 3 == 5
]
)

assert result == 0.5
assert s == 5
```

Use the `Write` object instead of `{...}` just because

```python
from phi import P, Rec, Read, Write

[result, s] = P.Pipe(
1.0, #input 1
(P + 3) / (P + 1), Write.s, #4 / 2 == 2, saved as 's'
dict(
x = P + 1 #2 + 1 == 3
,
y = P * 3 #2 * 3 == 6
),
[
Rec.x / Rec.y #3 / 6 == 0.5
,
Read.s + 3 # 2 + 3 == 5
]
)

assert result == 0.5
assert s == 5
```

Add an input `Val` of 9 on a branch and add to it 1 just for the sake of it

```python
from phi import P, Rec, Read, Write, Val

[result, s, val] = P.Pipe(
1.0, #input 1
(P + 3) / (P + 1), Write.s, #4 / 2 == 2, saved as 's'
dict(
x = P + 1 #2 + 1 == 3
,
y = P * 3 #2 * 3 == 6
),
[
Rec.x / Rec.y #3 / 6 == 0.5
,
Read.s + 3 # 2 + 3 == 5
,
Val(9) + 1 #input 9 and add 1, gives 10
]
)

assert result == 0.5
assert s == 5
assert val == 10
```

Do the previous only if `y > 7` else return `"Sorry, come back latter."`

```python
from phi import P, Rec, Read, Write, Val, If

[result, s, val] = P.Pipe(
1.0, #input 1
(P + 3) / (P + 1), Write.s, #4 / 2 == 2, saved as 's'
dict(
x = P + 1 #2 + 1 == 3
,
y = P * 3 #2 * 3 == 6
),
[
Rec.x / Rec.y #3 / 6 == 0.5
,
Read.s + 3 # 2 + 3 == 5
,
If( Rec.y > 7,
Val(9) + 1 #input 9 and add 1, gives 10
).Else(
Val("Sorry, come back latter.")
)
]
)

assert result == 0.5
assert s == 5
assert val == "Sorry, come back latter."
```

Now, what you have to understand that everything you've done with these expression is to create and apply a single function. Using `Make` we can get the standalone function and then use it to get the same values as before

```python
from phi import P, Rec, Read, Write, Val, If

f = P.Make(
(P + 3) / (P + 1), Write.s, #4 / 2 == 2, saved as 's'
dict(
x = P + 1 #2 + 1 == 3
,
y = P * 3 #2 * 3 == 6
),
[
Rec.x / Rec.y #3 / 6 == 0.5
,
Read.s + 3 # 2 + 3 == 5
,
If( Rec.y > 7,
Val(9) + 1 #input 9 and add 1, gives 10
).Else(
Val("Sorry, come back latter.")
)
]
)

[result, s, val] = f(1.0)

assert result == 0.5
assert s == 5
assert val == "Sorry, come back latter."
```
### Other Examples

```python
from phi import P, Obj

avg_word_length = P.Pipe(
"1 22 333",
Obj.split(" "), # ['1', '22', '333']
P.map(len), # [1, 2, 3]
P.sum() / P.len() # sum([1,2,3]) / len([1,2,3]) == 6 / 3 == 2
)

assert 2 == avg_word_length
```

```python
from phi import P

assert False == P.Pipe(
[1,2,3,4],
P.filter(P % 2 != 0) #[1, 3], keeps odds
.Contains(4) #4 in [1, 3] == False
)
```

```python
from phi import P, Obj, Ref

assert {'a': 97, 'b': 98, 'c': 99} == P.Pipe(
"a b c", Obj
.split(' ').Write.keys # keys = ['a', 'b', 'c']
.map(ord), # [ord('a'), ord('b'), ord('c')] == [97, 98, 99]
lambda it: zip(Ref.keys, it), # [('a', 97), ('b', 98), ('c', 99)]
dict # {'a': 97, 'b': 98, 'c': 99}
)
```

## Installation

pip install phi


#### Bleeding Edge

pip install git+https://github.com/cgarciae/phi.git@develop

## Status
* Version: **0.4.1**.
* Documentation coverage: 100%. Please create an issue if documentation is unclear, its of great priority for this library.
* Milestone: reach 1.0.0 after feedback from the community.