[Lasagna] revision to existing concept exercise

config.json

@@ -39,9 +39,7 @@
         "name": "Lasagna",
         "uuid": "39ebdd04-4f84-4817-bf9d-f1f9e066c283",
         "concepts": [
-          "functions",
-          "integer-introduction",
-          "comments"
+          "basics"
         ],
         "prerequisites": [],
         "status": "wip"

exercises/concept/lasagna/.docs/instructions.md

@@ -2,9 +2,18 @@
 
 In this exercise you're going to write some code to help you cook a brilliant lasagna from your favorite cooking book.
 
-You have three tasks, all related to the time spent cooking the lasagna.
+You have four tasks, all related to the time spent cooking the lasagna.
 
-## 1. Calculate the preparation time in minutes
+## 1. 
+
+Define the `expected_bake_time` constant that returns how many minutes the lasagna should bake in the oven. According to the cooking book, lasagna needs to be in the oven for a total of 60 minutes.
+
+```julia-repl
+julia> expected_bake_time
+60
+```
+
+## 2. Calculate the preparation time in minutes
 
 Define the `preptime` function that takes the number of layers you added to the lasagna as an argument and returns how many minutes you spent preparing the lasagna, assuming each layer takes you 2 minutes to prepare.
 
@@ -13,17 +22,16 @@ julia> preptime(4)
 8
 ```
 
-## 2. Calculate the remaining oven time in minutes
+## 3. Calculate the remaining oven time in minutes
 
-According to the cooking book, lasagna needs to be in the oven for a total of 60 minutes.
 Define the `remaining_time` function that takes the actual minutes the lasagna has been in the oven as a parameter and returns how many minutes the lasagna still has to remain in the oven.
 
 ```julia-repl
 julia> remaining_time(50)
 10
 ```
 
-## 3. Calculate the total working time in minutes
+## 4. Calculate the total working time in minutes
 
 Define the `total_working_time` function that takes two arguments: the first argument is the number of layers you added to the lasagna, and the second parameter is the number of minutes the lasagna has been in the oven.
 The function should return how many minutes in total you've worked on cooking the lasagna, which is the sum of the preparation time in minutes, and the time in minutes the lasagna has spent in the oven at the moment.

exercises/concept/lasagna/.docs/introduction.md

@@ -3,122 +3,120 @@
 The entire Julia track will require you to treat your solution like small libraries, i.e. you need to define functions, types etc. which will then be run against a test suite.
 For that reason, we will introduce named functions as the very first concept.
 
-## Functions
+Julia is a dynamic, strongly-typed programming langauge.
+The programming style is mainly functional, though with more flexibility than in languages such as Haskell.
 
-### Defining functions
+## Comments
 
-There are two common ways to define a named function in Julia:
+Two options are possible in Julia:
+- Single-line comments start with `#`
+- Multi-line comments start with `#=` and end with `=#`. Nesting is allowed.
 
-1. Using the `function` keyword
-
-    ```julia
-    function muladd(x, y, z)
-        return x * y + z
-    end
-    ```
+```julia
+# This is a single-line comment
 
-2. Using the "assignment form"
+x = 3  # This is an inline comment
 
-    ```julia
-    muladd(x, y, z) = x * y + z
-    ```
+#=
+	Multi-line comments can be used for longer explanations.
 
-    This is most commonly used for one-line function definitions or mathematical functions, where the function body is a single expression.
+	They are especially useful to comment out blocks of code during debugging.
+=#
+```
 
-### Invoking functions
+## Variables and assignment
 
-Invoking a function is done by specifying its name and passing arguments for each of the function's parameters:
+To create a variable, just assign a value to it:
 
-```julia
-# invoking a function
-muladd(10, 5, 1)
+```julia-repl
+julia> myvar = 42  # an integer
+42
 
-# and of course you can invoke a function within the body of another function:
-square_plus_one(x) = muladd(x, x, 1)
+julia> name = "Maria"  # strings are surrounded by double-quotes ""
+"Maria"
 ```
 
-## Integers and Arithmetic operations
+Types are an important subject in Julia, but for now it is best to ignore them them.
+The compiler will infer a suitable type for any expression you use.
 
-Integer literals in Julia are represented in the usual way.
-Underscores may be used as a digit separator.
+## Constants
 
-```julia-repl
-julia> 1
-1
-
-julia> -1234
--1234
+Global variables, created outside any function, are:
+- Allowed.
+- Sometimes necessary.
+- Usually discouraged (only within `*.jl` files; the REPL operates differently).
 
-julia> 1_234_567_890
-1234567890
-```
+If a value needs to be available throughout the program, but is not expected to change, use a constant instead.
 
-### Arithmetic operations
+Prefacing the assignemt with the `const` keyword allows the compiler to generate more efficient code.
 
-The standard prefix and infix operations are available: `+`, `-`, `*`, `%`.
+Accidentally trying to change the `const` value will give a warning:
 
 ```julia-repl
-julia> +16
-16
+julia> const answer = 42
+42
 
-julia> -16
--16
-
-julia> 16 + 6
-22
+julia> answer = 24
+WARNING: redefinition of constant Main.answer. This may fail, cause incorrect answers, or produce other errors.
+24
+```
 
-julia> 16 - 6
-10
+## Arithmetic operators
 
-julia> 16 * 6
-96
+These mostly work conventionally:
 
-julia> 16 % 6
-4
+```julia
+2 + 3  # 5 (addition)
+2 - 3  # -1 (subtraction)
+2 * 3  # 6 (mutlplication)
+8 / 2  # 4.0 (division with floating-point result)
+8 % 3  # 2 (remainder)
 ```
 
-#### Division
+## Functions
 
-Dividing two numbers with the `/` operator will result in a floating point value.
-To perform integer division
+There are two common ways to define a named function in Julia:
 
-- use the `div(x, y)` function, or
-- use the `÷` operator (Julia source code is unicode-aware)
+1. Using the `function` keyword
 
-```julia-repl
-julia> 16 / 6
-2.6666666666666665
+    ```julia
+    function muladd(x, y, z)
+        x * y + z
+    end
+    ```
 
-julia> div(16, 6)
-2
+    Indentation by 4 spaces is conventional for readability, but the compiler ignores this.
+    The `end` keyword is essential: more like Ruby than like Python.
 
-julia> 16 ÷ 6
-2
-```
+    Note that we could have written `return x * y + z`. 
+    However, Julia functions always return the last expression evaluated, so the `return` keyword is optional.
+    Many programmers prefer to include it to make their intentions more explicit.
 
-~~~~exercism/note
-It's natural to use Unicode symbols in Julia source files, typically in mathematical expressions.
-When using the Julia REPL, or in other Julia editing environments, the division symbol can be entered by typing `\div` followed by the `Tab` key.
-More details can be found in the manual at [Unicode Input][unicode].
+2. Using the "assignment form"
 
-[unicode]: https://docs.julialang.org/en/v1/manual/unicode-input/#Unicode-Input
-~~~~
+    ```julia
+    muladd(x, y, z) = x * y + z
+    ```
 
-## Comments
+    This is most commonly used for one-line function definitions or mathematical functions, where the function body is a single expression.
+    A `return` keyword is *never* used in the assignment form.
 
-Julia supports two kinds of comments.
-Single line comments are preceded by `#` and multiline comments are inserted between `#=` and `=#`.
+The two forms are equivalent, and are used in exactly the same way, so choose whichever is more readable.
+
+Invoking a function is done by specifying its name and passing arguments for each of the function's parameters:
 
 ```julia
-add(1, 3) # returns 4
+# invoking a function
+muladd(10, 5, 1)
 
-#= Some random code that's no longer needed but not deleted
-sub(x, y) = x - y
-mulsub(x, y, z) = sub(mul(x, y), z)
-=#
+# and of course you can invoke a function within the body of another function:
+square_plus_one(x) = muladd(x, x, 1)
 ```
 
-## Types
+## Naming conventions
+
+Like many languages, Julia requires that names (of variables, functions, and many other things) start with a letter, followed by any combination of letters, digits and underscores.
+
+By convention, variable, constant, and function names are *lowercase*, with underscores kept to a reasonable minimum.
 
-Depending on which other programming languages you know, you may expect parameters, variables or return values to have explicit type annotations.
-For now, assume that Julia will infer the types automagically and don't worry about them, we will get to the specifics of the type system in later exercises.
+However, Julia uses Unicode throughout, so "letter" is interpreted quite flexibly: not just *English* letters.

exercises/concept/lasagna/.docs/introduction.md.tpl

@@ -3,19 +3,5 @@
 The entire Julia track will require you to treat your solution like small libraries, i.e. you need to define functions, types etc. which will then be run against a test suite.
 For that reason, we will introduce named functions as the very first concept.
 
-## Functions
+%{concept:basics}
 
-%{concept:functions}
-
-## Integers and Arithmetic operations
-
-%{concept:integer-introduction}
-
-## Comments
-
-%{concept:comments}
-
-## Types
-
-Depending on which other programming languages you know, you may expect parameters, variables or return values to have explicit type annotations.
-For now, assume that Julia will infer the types automagically and don't worry about them, we will get to the specifics of the type system in later exercises.

exercises/concept/lasagna/.meta/config.json

@@ -4,7 +4,8 @@
   ],
   "contributors": [
     "ErikSchierboom",
-    "glennj"
+    "glennj",
+    "colinleach"
   ],
   "files": {
     "solution": [

exercises/concept/lasagna/.meta/design.md

@@ -2,7 +2,7 @@
 
 ## Goal
 
-The goal of this exercise is to teach the student the fundamentals of the Concept of functions in Julia, so that they are able to understand the basic structure of Exercism exercises.
+The goal of this exercise is to teach the student the fundamentals of the `basics` Concept in Julia, so that they are able to understand the basic structure of Exercism exercises.
 
 ## Learning objectives
 
@@ -11,17 +11,18 @@ The goal of this exercise is to teach the student the fundamentals of the Concep
 - Know how to call a function.
 - Know about implicit `return`s.
 - Know how to define an integer.
+- Know how to define a global constant.
 - Know how to use mathematical operators on integers.
 
 ## Out of scope
 
+Everthing beyond the simplest minimum for the first exercise of a novice.
+
 ## Concepts
 
 The Concepts this exercise practices are:
 
-- `functions`: Defining a function with one or more positional arguments that returns something. Bare minimum to be able to understand the basic structure of Exercism exercises.
-- `integers-introduction`: Present integer literals and basic arithmetic operations.
-- `comments`
+- `basics`: Defining a constant. Defining a function with one or more positional arguments that returns something. Bare minimum to be able to understand the basic structure of Exercism exercises.
 
 ## Prerequisites
 

exercises/concept/lasagna/.meta/exemplar.jl

@@ -1,3 +1,7 @@
+expected_bake_time = 60
+
 preptime(layers) = 2 * layers
-remaining_time(current_time) = 60 - current_time
+
+remaining_time(current_time) = expected_bake_time - current_time
+
 total_working_time(layers, current_time) = preptime(layers) + current_time

exercises/concept/lasagna/lasagna.jl

@@ -1,5 +1,8 @@
+# Define the `expected_bake_time` constant`
+
 # Define the `preptime(layers)` function.
 
 # Define the `remaining_time(time_in_oven)` function.
 
 # Define the `total_working_time(layers, time_in_oven)` function.
+

exercises/concept/lasagna/runtests.jl

@@ -3,6 +3,12 @@ using Test
 include("lasagna.jl")
 
 @testset verbose = true "tests" begin
+
+    @testset "expected bake time" begin
+        @test expected_bake_time == 60
+        @test isconst(typeof(expected_bake_time), expected_bake_time) == true
+    end
+
     @testset "preparation time" begin
         @test preptime(2) == 4
         @test preptime(3) == 6