New Concept Exercise: Freelancer Rates

concepts/arithmetic-operators/.meta/config.json

@@ -0,0 +1,7 @@
+{
+  "blurb": "Arithmetic operators are used to perform calculations with numeric values.",
+  "authors": [
+    "marianfoo"
+  ],
+  "contributors": []
+}

concepts/arithmetic-operators/about.md

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+# About
+
+ABAP supports the usual arithmetic operators for numeric values:
+
+- `+` adds values.
+- `-` subtracts values.
+- `*` multiplies values.
+- `/` divides values.
+- `MOD` returns the remainder of an integer division.
+
+```abap
+DATA total TYPE i.
+total = 6 + 4 * 2.
+
+DATA remaining_days TYPE i.
+remaining_days = 70 MOD 22.
+```
+
+Multiplication and division are evaluated before addition and subtraction. Use parentheses when a calculation should be grouped explicitly.
+
+```abap
+DATA result TYPE i.
+result = ( 6 + 4 ) * 2.
+```
+
+[arithmetic-expressions]: https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenarith_operators.htm

concepts/arithmetic-operators/introduction.md

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+# Introduction
+
+ABAP supports arithmetic operators for calculations with numeric values.
+
+```abap
+DATA day_rate TYPE p LENGTH 8 DECIMALS 2.
+day_rate = rate_per_hour * 8.
+```
+
+The basic operators are:
+
+- `+` for addition.
+- `-` for subtraction.
+- `*` for multiplication.
+- `/` for division.
+- `MOD` for the remainder of an integer division.
+
+```abap
+DATA full_months TYPE i.
+full_months = floor( num_days / 22 ).
+
+DATA remaining_days TYPE i.
+remaining_days = num_days MOD 22.
+```
+
+ABAP evaluates multiplication and division before addition and subtraction. Parentheses can be used to make the intended order explicit.
+
+```abap
+DATA discounted_rate TYPE p LENGTH 8 DECIMALS 2.
+discounted_rate = monthly_rate * ( 1 - discount ).
+```
+
+[arithmetic-expressions]: https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenarith_operators.htm

concepts/arithmetic-operators/links.json

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+[
+  {
+    "url": "https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenarith_operators.htm",
+    "description": "ABAP Arithmetic Operators"
+  }
+]

concepts/numbers/.meta/config.json

@@ -0,0 +1,7 @@
+{
+  "blurb": "Numbers represent integer and decimal values used in calculations.",
+  "authors": [
+    "marianfoo"
+  ],
+  "contributors": []
+}

concepts/numbers/about.md

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+# About
+
+ABAP has several numeric types. The most common ones for small introductory exercises are `i` for integer values and `p` for packed decimal values.
+
+Use `i` when a value must be a whole number, such as a count of days. Use a decimal type when a value can contain fractional digits, such as an hourly rate.
+
+```abap
+DATA hours_per_day TYPE i VALUE 8.
+DATA rate_per_hour TYPE p LENGTH 8 DECIMALS 2 VALUE '89.89'.
+
+DATA day_rate TYPE p LENGTH 8 DECIMALS 2.
+day_rate = hours_per_day * rate_per_hour.
+```
+
+Packed numbers are often used in business applications when a fixed number of decimal places is required. ABAP also has decimal floating point numbers (`decfloat16` and `decfloat34`) and binary floating point numbers (`f`). Binary floating point numbers can be useful for scientific calculations, but they are not a good default for money-like examples because many decimal fractions cannot be represented exactly.
+
+[numeric-types]: https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenbuiltin_types_numeric.htm

concepts/numbers/introduction.md

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+# Introduction
+
+ABAP has several numeric types. In this exercise, you will use two of them:
+
+- `i` for integer values, such as a number of days.
+- `p` for packed decimal values, such as an hourly rate or discount.
+
+```abap
+DATA billable_days TYPE i VALUE 22.
+DATA rate_per_hour TYPE p LENGTH 8 DECIMALS 2 VALUE '89.89'.
+```
+
+Packed numbers define their maximum length and number of decimal places. Decimal literals are commonly written as text values and converted to the target decimal type by the compiler or with `CONV`.
+
+```abap
+TYPES discount_rate TYPE p LENGTH 8 DECIMALS 6.
+
+DATA discount TYPE discount_rate.
+discount = CONV discount_rate( '0.15' ).
+```
+
+ABAP provides built-in numeric functions for rounding. The `floor` function rounds down to the nearest whole number, and `ceil` rounds up to the nearest whole number.
+
+```abap
+DATA full_months TYPE i.
+full_months = floor( 70 / 22 ).
+
+DATA rounded_cost TYPE i.
+rounded_cost = ceil( '14527.2' ).
+```
+
+[numeric-types]: https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenbuiltin_types_numeric.htm
+[floor]: https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenfloating_point_functions.htm

concepts/numbers/links.json

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+[
+  {
+    "url": "https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenbuiltin_types_numeric.htm",
+    "description": "ABAP Numeric Types"
+  },
+  {
+    "url": "https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenfloating_point_functions.htm",
+    "description": "ABAP Numeric Functions"
+  }
+]

config.json

@@ -43,6 +43,19 @@
         ],
         "prerequisites": [],
         "status": "wip"
+      },
+      {
+        "slug": "freelancer-rates",
+        "name": "Freelancer Rates",
+        "uuid": "0aff2fa7-55ea-47e9-af4a-78927d916baf",
+        "concepts": [
+          "numbers",
+          "arithmetic-operators"
+        ],
+        "prerequisites": [
+          "basics"
+        ],
+        "status": "wip"
       }
     ],
     "practice": [
@@ -453,6 +466,16 @@
       "uuid": "4a11ac86-a699-43e9-922e-f75681c86fd9",
       "slug": "basics",
       "name": "Basics"
+    },
+    {
+      "uuid": "fb681c0e-2bff-464e-9f4a-66a6ba13cd58",
+      "slug": "numbers",
+      "name": "Numbers"
+    },
+    {
+      "uuid": "3a8b883f-a4ea-4c5c-b2db-1d285acef657",
+      "slug": "arithmetic-operators",
+      "name": "Arithmetic Operators"
     }
   ],
   "key_features": [

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 `MOD`, the remainder operator, to calculate the number of days exceeding full months.
+- Add the discounted month rates and full day rates and round the result 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 their clients about the prices of certain projects.
+You will write a few utility methods to quickly calculate the costs for the clients.
+
+```exercism/note
+The `rate_per_hour` parameter and the `day_rate` method are related to money.
+The units of measurement are money for a unit of time: hours and days respectively.
+```
+
+## 1. Calculate the day rate given an hourly rate
+
+A client contacts the freelancer to enquire about their rates.
+The freelancer explains that they **_work 8 hours a day._**
+However, the freelancer knows only their hourly rates for the project.
+Help them estimate a day rate given an hourly rate.
+
+```abap
+DATA(freelancer_rates) = NEW zcl_freelancer_rates( ).
+
+freelancer_rates->day_rate( 89 ).
+// => 712
+```
+
+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 them calculate the number of days they would work until the budget is exhausted.
+The result _must_ be **rounded down** to the nearest whole number.
+
+```abap
+freelancer_rates->days_in_budget(
+  budget        = 20000
+  rate_per_hour = 89 ).
+// => 28
+```
+
+## 3. Calculate the discounted rate for large projects
+
+Often, the freelancer's clients hire them 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.
+Your excellent work-life balance means that you only work 22 days in each calendar month, so **_every month has 22 billable days._**
+Help them estimate their cost for such projects, given an hourly rate, the number of billable days the project contains, 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.
+
+```abap
+freelancer_rates->price_with_monthly_discount(
+  rate_per_hour = 89
+  num_days      = 230
+  discount      = '0.42' ).
+// => 97972
+```

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

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+# Introduction
+
+## Numbers
+
+ABAP has several numeric types. In this exercise, you will use two of them:
+
+- `i` for integer values, such as a number of days.
+- `p` for packed decimal values, such as an hourly rate or discount.
+
+```abap
+DATA billable_days TYPE i VALUE 22.
+DATA rate_per_hour TYPE p LENGTH 8 DECIMALS 2 VALUE '89.89'.
+```
+
+Packed numbers define their maximum length and number of decimal places.
+Decimal literals are commonly written as text values and converted to the target decimal type by the compiler or with `CONV`.
+
+```abap
+TYPES discount_rate TYPE p LENGTH 8 DECIMALS 6.
+
+DATA discount TYPE discount_rate.
+discount = CONV discount_rate( '0.15' ).
+```
+
+### Rounding
+
+ABAP provides built-in numeric functions for rounding.
+The `floor` function rounds down to the nearest whole number, and `ceil` rounds up to the nearest whole number.
+
+```abap
+DATA full_months TYPE i.
+full_months = floor( 70 / 22 ).
+
+DATA rounded_cost TYPE i.
+rounded_cost = ceil( '14527.2' ).
+```
+
+## Arithmetic Operators
+
+ABAP supports arithmetic operators for calculations with numeric values.
+
+```abap
+DATA day_rate TYPE p LENGTH 8 DECIMALS 2.
+day_rate = rate_per_hour * 8.
+```
+
+The basic operators are:
+
+- `+` for addition.
+- `-` for subtraction.
+- `*` for multiplication.
+- `/` for division.
+- `MOD` for the remainder of an integer division.
+
+```abap
+DATA remaining_days TYPE i.
+remaining_days = num_days MOD 22.
+```
+
+ABAP evaluates multiplication and division before addition and subtraction.
+Parentheses can be used to make the intended order explicit.
+
+```abap
+DATA discounted_rate TYPE p LENGTH 8 DECIMALS 2.
+discounted_rate = monthly_rate * ( 1 - discount ).
+```
+
+[numeric-types]: https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenbuiltin_types_numeric.htm
+[arithmetic-expressions]: https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abenarith_operators.htm

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

@@ -0,0 +1,23 @@
+{
+  "authors": [
+    "marianfoo"
+  ],
+  "contributors": [
+    "mbtools"
+  ],
+  "files": {
+    "solution": [
+      "zcl_freelancer_rates.clas.abap"
+    ],
+    "test": [
+      "zcl_freelancer_rates.clas.testclasses.abap"
+    ],
+    "exemplar": [
+      ".meta/zcl_freelancer_rates.clas.abap"
+    ]
+  },
+  "forked_from": [
+    "javascript/freelancer-rates"
+  ],
+  "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 use integer and decimal numeric values.
+- Know when an integer result is expected.
+- Know how to use packed numbers for decimal calculations.
+- Know how to round numbers down and up with `floor` and `ceil`.
+- Know how to use arithmetic operators (`+`, `-`, `*`, `/`, `MOD`).
+- Know how parentheses can make arithmetic precedence explicit.
+
+## Out of scope
+
+- Decimal floating point numbers.
+- Binary floating point numbers.
+- Parsing numeric text entered by a user.
+- Converting numbers to strings.
+
+## Concepts
+
+- `numbers`
+- `arithmetic-operators`
+
+## Prerequisites
+
+- `basics`