expanded readme

README.md

@@ -100,8 +100,8 @@ x := 5 # Global scope
 print(x) # prints 5
 
 if true then    # Define a new scope
-    x := 5000 # Shadow the value of x
-    print(x)  # prints 5000
+    x := 5000   # Shadow the value of x
+    print(x)    # prints 5000
 end             # Scope ends here
 
 print(x) # prints 5
@@ -121,6 +121,21 @@ end
 print(x) # prints 500
 ```
 
+### Set assignment
+
+You can unpack a set by assigning it to another set, eg
+
+```
+[x,y] = [5,6]
+
+print(x) # 5
+print(y) # 6
+```
+
+The sets must have the same length, otherwise the expression will error.
+
+This is useful for functions such as `head`
+
 ## If-else
 
 If expressions are defined as such
@@ -182,6 +197,86 @@ loop
 end
 ```
 
+In order to avoid the system hanging you can use the `break` keyword to stop a loop.
+
+```
+x := 5
+
+loop
+    if x = 0 then
+        break
+    end
+
+    x <- x-1
+end
+```
+
+## Functions
+
+Functions in openbirch allow you to define operations on a set of inputs. Functions are a first class type and can be defined as a set of arguments and a body.
+
+`args -> body`
+
+Heres a few examples:
+
+```
+# A function that takes 1 argument and returns the argument multiplied by 2
+f := x -> x*2
+
+f(4) # 8
+```
+
+If you want to use multiple arguments then supply a set as the argument
+
+```
+# A function that takes 2 arguments and adds them together
+f := [x,y] -> x+y
+
+f(2,3) # 5
+```
+
+Assigning a function to a name is the most common way of using them. This can be done in 2 ways
+
+```
+# Define f with a value that is a function
+f := x -> x*2
+
+# This does the same, but is more intuitive for people from a math background
+f(x) := x*2
+```
+
+### Currying
+
+Functions can return other functions. This creates a *closure*, that captures the variables passed to it.
+
+```
+add := x -> y -> x+y
+
+add(2)(3) # this evaluates to 5
+
+add2 := add(2) # This returns a closure where x is defined as 2
+
+print(add2) # this prints ( (x: 2) => ([y] -> x+y))
+            # What this shows is a closure that captures "x: 2",
+            # where inside is another function that defines y
+
+add2(5) # this is the same as add(2)(5) and returns 7.
+```
+
+### Built-in functions
+
+A few functions are defined by default. They provide additional functionality
+that has yet to be implemented into the language, such as syntax for indexing sets
+and getting their length.
+
+- `length(Set)` Returns the length of the given set
+- `get(Set,Constant)` Returns the value at the given index in the set
+- `head(Set)` Returns another Set consisting of `[head, [tail]]` where `head` is the first element in the set, and `tail` is all elements except the first element.
+- `map(Function, Set)` Returns a new set where every value has had the function applied to it.
+- `unset(String)` Undefines the given variable
+- `set_float_precision(Constant)` Sets the number of bits used for numbers. Default is 128bits
+- `get_float_precision(<optional Constant>)` Returns the current float precision. If a constant is given as the argument it will return the number of bits used for that constant.
+
 # Running
 
 ## Linux