universal-calculator/README.md

# [The Universal Calculator](https://git.ewanick.com/bill/universal-calculator)

Using the GHC REPL and Haskell to teach programming concepts through the guise of mathematics.  
A handy assistant to help you understand and solve maths problems.

- GHC = [Glasgow Haskell Compiler](https://www.haskell.org/ghc/)
- REPL = [Read Evaluate Print Loop](https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop)
- Haskell = [Lazy, Pure, Functional Programming Language](https://www.haskell.org/)

## How to use

```Haskell
λ> 5 * 5
25

λ> 1 + 5
6

λ> 10 / 2
5.0

λ> 10 `div` 2
5

λ> 10 `div` 3
3

λ> 10 / 3
3.3333333333333335

λ> :t sum
sum :: (Foldable t, Num a) => t a -> a

λ> :t sum [1..100]
sum [1..100] :: (Num a, Enum a) => a

λ> sum [1..100]
5050

λ> f x = 5*x^3 + 4*x + 2

λ> f 1
11

λ> f 10
5042

λ> f 100
5000402

λ> map f [1..10]
[11,50,149,338,647,1106,1745,2594,3683,5042]

λ> putStrLn "Hello, world!"
Hello, world!
```

## How to install

- Use the DeterminateSystems installer to install Nix with Flakes.
  - <https://github.com/DeterminateSystems/nix-installer>
- `cd` into the top level of this repo.
- `nix develop` and let Nix load the flake and set everything up.
- `ghci` and get computing!
  - To enable performance timings after every input, type `λ> :set +s` in the REPL
  - See other initial commands being run in the `.ghci` file.