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Functional Programming/Basic Haskell.md

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+---
+type: mixed
+---
+
+## Function definitions
+![](Pasted%20image%2020241125164049.png)
+
+- We don't have a return, we have an expression
+- Calling a function is done like this:
+```haskell
+name arg1 arg2 ... argn
+```
+Or in this case: 
+``` haskell
+add 1 2 -- This will return 3
+```
+
+
+## Types
+```haskell
+name :: <type>
+```
+
+### Integer
+```haskell
+x :: Integer
+x = 1
+```
+
+### Boolean
+```haskell
+y :: Bool
+y = True
+```
+
+### Float
+```haskell
+z :: Float
+z = 1.6
+```
+- Data Types
+
+	- **Int**: platform-dependent precision integers
+	- **Char**: character literals, functions from Data.Char module (e.g., isSpace, isDigit, isAlpha, isLower, isUpper, toLower, toUpper, digitToInt)
+	- **Tuple types**: (e1, ..., en), functions fst and snd for pairs
+
+- Type classes
+	- `Num`: numeric types (e.g., Int, Integer, Float, Double)
+	- `Eq`: equality types, with operators `==` and `/=`
+	- `Ord`: ordered types, with operators `<` and `<=`
+
+[More types here](https://www.tutorialspoint.com/haskell/haskell_types_and_type_class.htm)
+
+## Infix functions
+
+- Functions written **between** their arguments, rather than before them.
+- `5 + 3` is an infix function
+- By default, functions with symbols (like `+`, `-`, `*`) are infix.
+- You can also make any function infix by surrounding it with backticks (`` ` ``).
+
+Continuing with the `add` example, we could call it like this:
+```haskell
+add 5 3 -- 8
+```
+but we could also do this
+
+```haskell
+5 `add` 3
+```
+
+This achieves more natural placement of the function (in some cases). 
+
+## Types in functions
+
+We define them as a chain of types for the arguments (including the return type) with `->`
+In the `add` example:
+
+```haskell
+add :: Integer -> Integer -> Integer
+add x y = x + y
+```
+
+
+## Let
+- Save the result of an expression and then return it
+- Defines variables **before** the main expression
+```haskell
+let <name> = <expression> in <result>
+```
+
+i.e.
+```haskell
+let x = 5
+    y = 10
+in x + y -- This will "return" x+y = 15
+```
+
+
+## Where
+- Inverse of let - defines variables **after** the main expression
+- Makes more intuitive mathematical sense
+
+```haskell
+<result> where <name> = <expression>
+```
+
+i.e.
+```haskell
+x + y where
+  x = 5
+  y = 10
+```
+
+
+
+## If branches
+### If then else (ternary)
+```haskell
+equalize x y =
+  if xLarger then x - 1 else y - 1
+  where
+    xLarger = x > y
+
+```
+
+