pkg environments for each folder, fix typos

Author: masenka31

docs/make.jl

@@ -25,7 +25,7 @@ lecture_01 = [
 ]
 
 lecture_02 = [
-    "Funcion basics" => "./lecture_02/functions.md",
+    "Function basics" => "./lecture_02/functions.md",
     "Conditional evaluations" => "./lecture_02/conditions.md",
     "Loops and iterators" => "./lecture_02/loops.md",
     "Soft local scope" => "./lecture_02/scope.md",

docs/src/lecture_02/functions.md

@@ -27,9 +27,77 @@ The function definition consists of multiple parts:
 Note that not all parts of the function definition above are mandatory. The following parts are optional:
 
 - type annotations
-- separator of positinal and keywor arguments
+- separator of positional and keyword arguments
 - `return` keyword
 
-However, we highly recommend to use these optional features when writing own functions, since it will improve code readibility and prevent unwanted errors. 
+However, we highly recommend to use these optional features when writing your own functions, since it will improve code readability and prevent unwanted errors.
 
-We will discuss the function declaration in more detail [later](@ref Functions).
+!!! warning "Exercise:"
+    Test how the function behaves with different input values. Test what happens when the input is not a real number, i.e. `x = "a"`.
+
+!!! details "Solution:"
+    Positional arguments do not need to be named:
+    ```jldoctest functions
+    julia> quadratic(2)
+    (7, 5)
+    ```
+
+    but the keyword arguments have to be specified. Their order of being called does not matter.
+    ```jldoctest functions
+    julia> quadratic(2; b=3, a=1)
+    (11, 7)
+    ```
+
+    When a function has specific type annotation, the function throws a `MethodError`, because the function specifically needs `x` to be of type `Real`.
+    ```jldoctest functions
+    julia> quadratic("a")
+    ERROR: MethodError: no method matching quadratic(::String)
+
+    Closest candidates are:
+      quadratic(!Matched::Real; a, b, c)
+       @ Main none:1
+
+    Stacktrace:
+     [1] top-level scope
+       @ none:1
+    ```
+
+    This is different to a a case when we would define the function without the type annotation:
+
+    ```jldoctest functions; output = false
+    function quadratic2(x; a = 1, b = 1, c = 1)
+        value = a*x^2 + b*x + c 
+        deriv = 2* a*x + b
+
+        return value, deriv
+    end
+
+    # output
+    quadratic2 (generic function with 1 method)
+    ```
+    
+    which returns a different error when calling for `x = "a"`:
+
+    ```jldoctest functions
+    julia> quadratic2("a")
+    ERROR: MethodError: no method matching *(::Int64, ::String)
+
+    Closest candidates are:
+      *(::Any, ::Any, !Matched::Any, !Matched::Any...)
+       @ Base operators.jl:587
+      *(::Real, !Matched::Complex{Bool})
+       @ Base complex.jl:327
+      *(!Matched::Missing, ::Union{AbstractChar, AbstractString})
+       @ Base missing.jl:184
+      ...
+
+    Stacktrace:
+     [1] quadratic2(x::String; a::Int64, b::Int64, c::Int64)
+       @ Main ./none:2
+     [2] quadratic2(x::String)
+       @ Main ./none:1
+     [3] top-level scope
+       @ none:1
+    ```
+
+We will discuss the function declaration in more detail [later](@ref Functions).

docs/src/lecture_03/pkg.md

@@ -187,3 +187,24 @@ The `Project.toml` file describes the project on a high level. It contains the p
 ```
 
 Different users may use different package versions. Since updated packages provide different functionality for some functions, instantiating is extremely useful for reproducing code across multiple computers.
+
+## Scripts environments
+
+The [scripts repository](https://github.com/JuliaTeachingCTU/Julia-for-Optimization-and-Learning-Scripts) contains scripts for each lecture. For every lecture, a `Project.toml` file with necessary packages is provided.
+
+VS Code + Julia extension activate a parent folder default environment automatically when you start the Julia REPL with Cmd + Shift + P and choose `Julia: Start REPL` or use the Shift + Enter keyboard shortcut to run a line of a specific script. Since the parent environment is `Julia-for-Optimization-and-Learning`, this environment is activated.
+
+You can either use
+
+```julia
+using Pkg
+Pkg.activate(pwd() * "/lecture_03")
+```
+
+and change the corresponding lecture number, or go to the REPL package manager and activate the environment with
+
+```julia
+(Julia-for-Optimization-and-...) pkg> activate lecture_03
+```
+
+Don't forget to check all packages are installed with `Pkg.status()` or `pkg> st` and `instantiate` if some packages are missing.