Concept exercise for "Numbers" (closes #599)

config.json

@@ -57,6 +57,17 @@
         "prerequisites": [],
         "status": "wip"
       },
+      {
+        "uuid": "88baa5ab-dacb-4fab-8f16-4f3ed726b27b",
+        "slug": "freelancer-rates",
+        "name": "Freelancer Rates",
+        "concepts": ["numbers"],
+        "prerequisites": [
+          "basics",
+          "includes"
+        ],
+        "status": "wip"
+      },
       {
         "slug": "last-will",
         "name": "Last Will",

exercises/concept/freelancer-rates/.docs/hints.md

@@ -0,0 +1,24 @@
+# Hints
+
+## General
+
+- Browse the [`cmath` reference][cmath-reference] to learn about common mathematical operations and transformations that work with `doubles`.
+
+## 1. Calculate the daily rate given an hourly rate
+
+- Basic arithmetic operations where one argument is an `int`, and the other is a `double`, will return a `double`.
+
+## 2. Calculate a discounted price
+
+- Basic arithmetic operations where one argument is an `int`, and the other is a `double`, will return a `double`.
+
+## 3. Calculate the monthly rate, given an hourly rate and a discount
+
+- There is a [function in the `cmath` header][cmath-ceil] for rounding up.
+
+## 4. Calculate the number of workdays given a budget, hourly rate, and discount
+
+- Casting a `double` to an `int` will truncate the number at the decimal point.
+
+[cmath-reference]: https://en.cppreference.com/w/cpp/header/cmath
+[cmath-ceil]: https://en.cppreference.com/w/cpp/numeric/math/ceil

exercises/concept/freelancer-rates/.docs/instructions.md

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+# Instructions
+In this exercise, you'll be writing code to help a freelancer communicate with a project manager.
+Your task is to provide a few utilities to quickly calculate daily and monthly rates, optionally with a given discount.
+
+We first establish a few rules between the freelancer and the project manager:
+
+- The daily rate is 8 times the hourly rate.
+- A month has 22 billable days.
+
+Sometimes, the freelancer is offering to apply a discount on their daily rate (for example for their most loyal customers or not-for-profit customers).
+
+Discounts are modeled as fractional numbers representing percentages, for example, `25.0` (25%).
+
+## 1. Calculate the daily rate given an hourly rate
+
+Implement a function to calculate the daily rate given an hourly rate:
+
+```cpp
+daily_rate(60)
+// => 480.0
+```
+
+The returned daily rate should be of type `double`.
+
+## 2. Calculate a discounted price
+
+Implement a function to calculate the price after a discount.
+
+```cpp
+apply_discount(150, 10)
+// => 135.0
+```
+
+The returned value should always be of type `double`, not rounded in any way.
+
+## 3. Calculate the monthly rate, given an hourly rate and a discount
+
+Implement a function to calculate the monthly rate, and apply a discount.
+
+```cpp
+monthly_rate(77, 10.5)
+// => 12130
+```
+
+The returned monthly rate should be rounded up (take the ceiling) to the nearest integer.
+
+## 4. Calculate the number of complete workdays given a budget, hourly rate, and discount
+
+Implement a function that takes a budget, an hourly rate, and a discount, and calculates how many complete days of work that covers.
+
+```cpp
+days_in_budget(20'000, 80, 11.0)
+// => 35
+```
+
+The returned number of days should be rounded down (take the floor) to the next integer.

exercises/concept/freelancer-rates/.docs/introduction.md

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+# Introduction
+
+## Numbers
+The built-in number types in C++ can be divided into integers and floating points.
+Integers are whole numbers like `0`, `691`, or `-2`.
+Floating point numbers are numbers with a decimal point like `6.02214076`, `0.1`, or `-1.616`.
+
+### Integers
+The following example shows the declaration and initialization of four different variables 
+
+```cpp
+int m_morales{9241};              // base 10: 0-9
+int a_apaec{0x24CD};              // base 16: 0-9 and A-F
+int m_gargan{0b10010000011001};   // base  2: 0-1
+int b_reilly{022031};             // base  8: 0-7
+                                  // Leading with a 0 not the letter o.
+```
+When you assign a value to an `int` variable, you can do so directly with a literal.
+A literal is a hard-coded number like `9241`.
+There are different integer literals for several bases of the representation.
+Decimal integer literals are the most common and use the digits `0` to `9`.
+By adding a special prefix, like `0x`, it is possible to use other bases.
+The example above shows the number `9421` in its four representations and prefixes.
+All variables are initialized to the same value.
+
+For more details on the different representation systems, take a look at [a small tutorial][cpp_numerical_bases].
+
+You can use an apostrophe to separate digits for easier readability.
+`9'241` is the same as `0b0100'100'0001'1001` or `92'4'1`.
+
+### Floating-Point Numbers
+
+The floating-point literals come in two flavors. 
+In addition to the intuitive `0.0024` it is possible to use its scientific notation `2.4e-3`.
+The most common floating-point type is `double`.
+
+### Arithmetic
+
+C++ supports `+`, `-`, `*`, `/`, `(` and `)` and `%` to form expressions.
+The result from the operation between two integers is also an integer.
+`5 / 2` will return `2`.
+When one of the involved types is a floating-point type, the result will also be of a floating-point.
+`5.0 / 2` and `5 / 2.0` will return `2.5`.
+`%` is the remainder operator and will return the remainder of an integer division: `5%3` is `2`.
+
+[cpp_numerical_bases]: https://cplusplus.com/doc/hex/

exercises/concept/freelancer-rates/.docs/introduction.md.tpl

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+# Introduction
+
+%{concept:numbers}

exercises/concept/freelancer-rates/.meta/config.json

@@ -0,0 +1,21 @@
+{
+  "authors": [
+    "vaeng"
+  ],
+  "files": {
+    "solution": [
+      "freelancer_rates.cpp"
+    ],
+    "test": [
+      "freelancer_rates_test.cpp"
+    ],
+    "exemplar": [
+      ".meta/exemplar.cpp"
+    ]
+  },
+  "forked_from": [
+    "elixir/freelancer-rates"
+  ],
+  "icon": "freelancer-rates",
+  "blurb": "Learn about integers and floating point numbers by helping a freelancer communicate with a project manager about billing."
+}

exercises/concept/freelancer-rates/.meta/design.md

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+# Design
+
+## Learning objectives
+
+- Know how to write integer literals.
+- Know how to write floating point literals.
+- Know their underlying type (double precision).
+- Know how to truncate floating point numbers (via cast to int or `cmath` header)
+- Know how to convert floats to integers.
+
+## Out of scope
+
+- Parsing integers and floats from strings.
+- Converting integers and floats to strings.
+
+## Concepts
+
+- `numbers`
+
+## Prerequisites
+
+- `basics`
+- `includes`
+
+## Analyzer
+
+- assert that `monthly_rate` calls `apply_discount`
+- assert that `monthly_rate` calls `daily_rate`
+- assert that `days_in_budget` calls `apply_discount` 
+- assert that `days_in_budget` calls `daily_rate`

exercises/concept/freelancer-rates/.meta/exemplar.cpp

@@ -0,0 +1,35 @@
+// INFO: Headers from the standard library should be inserted at the top via
+#include <cmath>
+
+// daily_rate calculates the daily rate given an hourly rate
+double daily_rate(double hourly_rate) {
+    double hours_per_day{8.0};
+    return hours_per_day * hourly_rate;
+}
+
+// apply_discount calculates the price after a discount
+double apply_discount(double before_discount, double discount) {
+    return before_discount * (100.0 - discount) / 100.0;
+}
+
+// monthly_rate calculates the monthly rate, given an hourly rate and a discount
+// The returned monthly rate is rounded up to the nearest integer.
+int monthly_rate(double hourly_rate, double discount) {
+    double per_day{daily_rate(hourly_rate)};
+    int workdays_per_month{22};
+    double per_month{per_day * workdays_per_month};
+    double after_discount{apply_discount(per_month, discount)};
+    int rounded_up{std::ceil(after_discount)};
+
+    return rounded_up;
+}
+
+// days_in_budget calculates the number of workdays given a budget, hourly rate,
+// and discount The returned number of days is rounded down (take the floor) to
+// the next integer.
+int days_in_budget(int budget, double hourly_rate, double discount) {
+    double discounted_per_hour{apply_discount(hourly_rate, discount)};
+    double discounted_daily{daily_rate(discounted_per_hour)};
+
+    return static_cast<int>(budget / discounted_daily);
+}

exercises/concept/freelancer-rates/CMakeLists.txt

@@ -0,0 +1,64 @@
+# Basic CMake project
+cmake_minimum_required(VERSION 3.5.1)
+
+# Get the exercise name from the current directory
+get_filename_component(exercise ${CMAKE_CURRENT_SOURCE_DIR} NAME)
+
+# Name the project after the exercise
+project(${exercise} CXX)
+
+# Get a source filename from the exercise name by replacing -'s with _'s
+string(REPLACE "-" "_" file ${exercise})
+
+# Implementation could be only a header
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${file}.cpp)
+    set(exercise_cpp ${file}.cpp)
+else()
+    set(exercise_cpp "")
+endif()
+
+# Use the common Catch library?
+if(EXERCISM_COMMON_CATCH)
+    # For Exercism track development only
+    add_executable(${exercise} ${file}_test.cpp $<TARGET_OBJECTS:catchlib>)
+elseif(EXERCISM_TEST_SUITE)
+    # The Exercism test suite is being run, the Docker image already
+    # includes a pre-built version of Catch.
+    find_package(Catch2 REQUIRED)
+    add_executable(${exercise} ${file}_test.cpp)
+    target_link_libraries(${exercise} PRIVATE Catch2::Catch2WithMain)
+    # When Catch is installed system wide we need to include a different
+    # header, we need this define to use the correct one.
+    target_compile_definitions(${exercise} PRIVATE EXERCISM_TEST_SUITE)
+else()
+    # Build executable from sources and headers
+    add_executable(${exercise} ${file}_test.cpp test/tests-main.cpp)
+endif()
+
+set_target_properties(${exercise} PROPERTIES
+    CXX_STANDARD 17
+    CXX_STANDARD_REQUIRED OFF
+    CXX_EXTENSIONS OFF
+)
+
+set(CMAKE_BUILD_TYPE Debug)
+
+if("${CMAKE_CXX_COMPILER_ID}" MATCHES "(GNU|Clang)")
+    set_target_properties(${exercise} PROPERTIES
+        COMPILE_FLAGS "-Wall -Wextra -Wpedantic -Werror"
+    )
+endif()
+
+# Configure to run all the tests?
+if(${EXERCISM_RUN_ALL_TESTS})
+    target_compile_definitions(${exercise} PRIVATE EXERCISM_RUN_ALL_TESTS)
+endif()
+
+# Tell MSVC not to warn us about unchecked iterators in debug builds
+if(${MSVC})
+    set_target_properties(${exercise} PROPERTIES
+        COMPILE_DEFINITIONS_DEBUG _SCL_SECURE_NO_WARNINGS)
+endif()
+
+# Run the tests on every build
+add_custom_target(test_${exercise} ALL DEPENDS ${exercise} COMMAND ${exercise})

exercises/concept/freelancer-rates/freelancer_rates.cpp

@@ -0,0 +1,32 @@
+// INFO: Headers from the standard library should be inserted at the top via
+// #include <LIBRARY_NAME>
+
+// daily_rate calculates the daily rate given an hourly rate
+double daily_rate(double hourly_rate) {
+    // TODO: Implement a function to calculate the daily rate given an hourly
+    // rate
+    return 0.0;
+}
+
+// apply_discount calculates the price after a discount
+double apply_discount(double before_discount, double discount) {
+    // TODO: Implement a function to calculate the price after a discount.
+    return 0.0;
+}
+
+// monthly_rate calculates the monthly rate, given an hourly rate and a discount
+// The returned monthly rate is rounded up to the nearest integer.
+int monthly_rate(double hourly_rate, double discount) {
+    // TODO: Implement a function to calculate the monthly rate, and apply a
+    // discount.
+    return 0;
+}
+
+// days_in_budget calculates the number of workdays given a budget, hourly rate,
+// and discount The returned number of days is rounded down (take the floor) to
+// the next integer.
+int days_in_budget(int budget, double hourly_rate, double discount) {
+    // TODO: Implement a function that takes a budget, an hourly rate, and a
+    // discount, and calculates how many complete days of work that covers.
+    return 0;
+}