New Concept Exercise: Freelancer Rates

config.json

@@ -20,6 +20,19 @@
   },
   "exercises": {
     "concept": [
+      {
+        "slug": "freelancer-rates",
+        "name": "Freelancer Rates",
+        "uuid": "0aff2fa7-55ea-47e9-af4a-78927d916baf",
+        "concepts": [
+          "numbers",
+          "arithmetic-operators"
+        ],
+        "prerequisites": [
+          "basics"
+        ],
+        "status": "beta"
+      },
       {
         "slug": "lasagna",
         "name": "Lucian's Luscious Lasagna",

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

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+# Hints
+
+## 1. Calculate the day rate given an hourly rate
+
+- Use the arithmetic operators as mentioned in the introduction of this exercise.
+
+## 2. Calculate the number of workdays given a budget
+
+- First determine the day rate, then calculate the number of days, and finally round that number down.
+
+## 3. Calculate the discounted rate for large projects
+
+- Round down the result from division to get the number of full months.
+- `100% - discount` equals the percentage charged after the discount is applied.
+- Use `%`, the remainder operator, to calculate the number of days exceeding full months.
+- Add the discounted month rates and full day rates and round it up

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

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+# Instructions
+
+In this exercise you will be writing code to help a freelancer communicate with his clients about the prices of certain projects. You will write a few utility functions to quickly calculate the costs for the clients.
+
+## 1. Calculate the day rate given an hourly rate
+
+A client contacts the freelancer to enquire about his rates.
+The freelancer explains that he **_works 8 hours a day._**
+However, the freelancer knows only his hourly rates for the project.
+Help him estimate a day rate given an hourly rate.
+
+```c
+DATA(lcl_freelancer_rates) = new zcl_freelancer_rates( ).
+DATA(lv_day_rate) = lcl_freelancer_rates->day_rate( 16 ).
+WRITE |My Day Rate is: { lv_day_rate }|.
+// => My Day Rate is: 128
+```
+
+The day rate does not need to be rounded or changed to a "fixed" precision.
+
+## 2. Calculate the number of workdays given a fixed budget
+
+Another day, a project manager offers the freelancer to work on a project with a fixed budget.
+Given the fixed budget and the freelancer's hourly rate, help him calculate the number of days he would work until the budget is exhausted.
+The result _must_ be **rounded** to the nearest number with 2 decimal places.
+
+```c
+DATA(lcl_freelancer_rates) = new zcl_freelancer_rates( ).
+DATA(lv_days_in_budget) = lcl_freelancer_rates->DAYS_IN_BUDGET( budget = 1280 rate_per_hour = 16  ).
+WRITE |Budget would last for { lv_days_in_budget } days.|.
+// => Budget would last for 10 days.
+```
+
+## 3. Calculate the discounted rate for large projects
+
+Often, the freelancer's clients hire him for projects spanning over multiple months.
+In these cases, the freelancer decides to offer a discount for every full month, and the remaining days are billed at day rate.
+**_Every month has 22 billable days._**
+Help him estimate his cost for such projects, given an hourly rate, the number of days the project spans, and a monthly discount rate.
+The discount is always passed as a number, where `42%` becomes `0.42`. The result _must_ be **rounded up** to the nearest whole number.
+
+```javascript
+priceWithMonthlyDiscount(89, 230, 0.42);
+// => 97972
+```

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

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+# Introduction
+
+## Numbers
+
+Many programming languages have specific numeric types to represent different types of numbers, but JavaScript only has two:
+
+- `number`: a numeric data type in the double-precision 64-bit floating-point format (IEEE 754).
+  Examples are `-6`, `-2.4`, `0`, `0.1`, `1`, `3.14`, `16.984025`, `25`, `976`, `1024.0` and `500000`.
+- `bigint`: a numeric data type that can represent _integers_ in the arbitrary precision format.
+  Examples are `-12n`, `0n`, `4n`, and `9007199254740991n`.
+
+If you require arbitrary precision or work with extremely large numbers, use the `bigint` type.
+Otherwise, the `number` type is likely the better option.
+
+### Rounding
+
+There is a built-in global object called `Math` that provides various [rounding functions][ref-math-object-rounding]. For example, you can round down (`floor`) or round up (`ceil`) decimal numbers to the nearest whole numbers.
+
+```javascript
+Math.floor(234.34); // => 234
+Math.ceil(234.34); // => 235
+```
+
+## Arithmetic Operators
+
+JavaScript provides 6 different operators to perform basic arithmetic operations on numbers.
+
+- `+`: The addition operator is used to find the sum of numbers.
+- `-`: The subtraction operator is used to find the difference between two numbers
+- `*`: The multiplication operator is used to find the product of two numbers.
+- `/`: The division operator is used to divide two numbers.
+
+```javascript
+2 - 1.5; //=> 0.5
+19 / 2; //=> 9.5
+```
+
+- `%`: The remainder operator is used to find the remainder of a division performed.
+
+  ```javascript
+  40 % 4; // => 0
+  -11 % 4; // => -3
+  ```
+
+- `**`: The exponentiation operator is used to raise a number to a power.
+
+  ```javascript
+  4 ** 3; // => 64
+  4 ** 1 / 2; // => 2
+  ```
+
+### Order of Operations
+
+When using multiple operators in a line, JavaScript follows an order of precedence as shown in [this precedence table][mdn-operator-precedence].
+To simplify it to our context, JavaScript uses the PEDMAS (Parentheses, Exponents, Division/Multiplication, Addition/Subtraction) rule we've learnt in elementary math classes.
+
+<!-- prettier-ignore-start -->
+```javascript
+const result = 3 ** 3 + 9 * 4 / (3 - 1);
+// => 3 ** 3 + 9 * 4/2
+// => 27 + 9 * 4/2
+// => 27 + 18
+// => 45
+```
+<!-- prettier-ignore-end -->
+
+### Shorthand Assignment Operators
+
+Shorthand assignment operators are a shorter way of writing code conducting arithmetic operations on a variable, and assigning the new value to the same variable.
+For example, consider two variables `x` and `y`.
+Then, `x += y` is same as `x = x + y`.
+Often, this is used with a number instead of a variable `y`.
+The 5 other operations can also be conducted in a similar style.
+
+```javascript
+let x = 5;
+x += 25; // x is now 30
+
+let y = 31;
+y %= 3; // y is now 1
+```
+
+[mdn-operator-precedence]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence#table
+[ref-math-object-rounding]: https://javascript.info/number#rounding

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

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+{
+    "authors": [
+      "marianfoo"
+    ],
+    "contributors": [
+    ],
+    "files": {
+      "solution": [
+        "zcl_freelancer_rates.clas.abap"
+      ],
+      "test": [
+        "zcl_freelancer_rates.clas.testclasses.abap"
+      ],
+      "exemplar": [
+        ".meta/zcl_freelancer_rates.clas.abap"
+      ]
+    },
+    "blurb": "Learn about numbers whilst helping a freelancer communicate with a project manager about day- and month rates."
+  }

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

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+# Design
+
+## Learning objectives
+
+- Know how to write floating point literals.
+- Know their underlying type (double precision).
+- Know their basic limitations (not all numbers can be represented, e.g. `0.1 + 0.2`).
+- Know how to truncate floating point numbers to a certain decimal place (`Math.ceil`, `Math.floor`, `Math.round`)
+- Know how to use arithmetic operators (`+`, `-`, `*`, `/`, `%`, `**`)
+- Learn about shorthand assignment operators (`+=`, etc.)
+
+## Out of scope
+
+- Parsing integers and floats from strings.
+- Converting integers and floats to strings.
+
+## Concepts
+
+- `numbers`
+- `arithmetic-operators`
+
+## Prerequisites
+
+- `basics`

exercises/concept/freelancer-rates/.meta/zcl_freelancer_rates.clas.abap

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+CLASS zcl_freelancer_rates DEFINITION
+  PUBLIC
+  FINAL
+  CREATE PUBLIC .
+
+  PUBLIC SECTION.
+
+    METHODS day_rate
+      IMPORTING
+        !rate_per_hour TYPE f
+      RETURNING
+        VALUE(result)  TYPE f .
+    METHODS days_in_budget
+      IMPORTING
+        !budget        TYPE f
+        !rate_per_hour TYPE f
+      RETURNING
+        VALUE(result)  TYPE i .
+    METHODS price_with_monthly_discount
+      IMPORTING
+        !rate_per_hour TYPE f
+        !num_days      TYPE f
+        !discount      TYPE f
+      RETURNING
+        VALUE(result)  TYPE f .
+  PROTECTED SECTION.
+  PRIVATE SECTION.
+ENDCLASS.
+
+
+
+CLASS zcl_freelancer_rates IMPLEMENTATION.
+
+
+
+  METHOD day_rate.
+    result = round( val  = rate_per_hour * 8 dec = 2 ) .
+  ENDMETHOD.
+
+  METHOD days_in_budget.
+    result = floor( budget / day_rate( rate_per_hour ) ).
+  ENDMETHOD.
+
+
+  METHOD price_with_monthly_discount.
+    DATA(lv_months) = floor( num_days / 22 ).
+    DATA(lv_monthly_rate) = 22 * day_rate( rate_per_hour ).
+    DATA(lv_monthly_discount_rate) = ( 1 - discount ) * lv_monthly_rate.
+
+    DATA(lv_extra_days) = num_days MOD 22.
+    DATA(lv_price_extra_days) = lv_extra_days * day_rate( rate_per_hour ).
+
+    result = ceil( lv_months * lv_monthly_discount_rate + lv_price_extra_days ).
+  ENDMETHOD.
+ENDCLASS.

exercises/concept/freelancer-rates/package.devc.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<abapGit version="v1.0.0" serializer="LCL_OBJECT_DEVC" serializer_version="v1.0.0">
+ <asx:abap xmlns:asx="http://www.sap.com/abapxml" version="1.0">
+  <asx:values>
+   <DEVC>
+    <CTEXT>Exercism: Freelancer Rates</CTEXT>
+   </DEVC>
+  </asx:values>
+ </asx:abap>
+</abapGit>

exercises/concept/freelancer-rates/zcl_freelancer_rates.clas.abap

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+CLASS zcl_freelancer_rates DEFINITION
+  PUBLIC
+  FINAL
+  CREATE PUBLIC .
+
+  PUBLIC SECTION.
+
+    METHODS day_rate
+      IMPORTING
+        !rate_per_hour TYPE f
+      RETURNING
+        VALUE(result)  TYPE f.
+
+    METHODS days_in_budget
+      IMPORTING
+        !budget        TYPE f
+        !rate_per_hour TYPE f
+      RETURNING
+        VALUE(result)  TYPE i.
+
+    METHODS price_with_monthly_discount
+      IMPORTING
+        !rate_per_hour TYPE f
+        !num_days      TYPE f
+        !discount      TYPE f
+      RETURNING
+        VALUE(result)  TYPE f.
+
+  PROTECTED SECTION.
+  PRIVATE SECTION.
+ENDCLASS.
+
+
+
+CLASS zcl_freelancer_rates IMPLEMENTATION.
+
+
+  METHOD days_in_budget.
+* add solution here
+  ENDMETHOD.
+
+
+  METHOD day_rate.
+* add solution here
+  ENDMETHOD.
+
+
+  METHOD price_with_monthly_discount.
+* add solution here
+  ENDMETHOD.
+ENDCLASS.