{"id":2632,"date":"2026-02-05T08:05:38","date_gmt":"2026-02-05T08:05:38","guid":{"rendered":"https:\/\/demo.materiamedica.net\/demo6\/?p=2632"},"modified":"2026-02-05T08:05:38","modified_gmt":"2026-02-05T08:05:38","slug":"chapter-24-swift-arithmetic-operators","status":"publish","type":"post","link":"https:\/\/demo.materiamedica.net\/demo6\/chapter-24-swift-arithmetic-operators\/","title":{"rendered":"Chapter 24: Swift Arithmetic Operators"},"content":{"rendered":"1. What are Arithmetic Operators?<\/h3>\n
Arithmetic operators are the mathematical symbols<\/strong> you use to perform calculations:<\/p>\n\n- + addition<\/li>\n
- – subtraction<\/li>\n
- * multiplication<\/li>\n
- \/ division<\/li>\n
- % remainder (modulo)<\/li>\n<\/ul>\n
These operators work with numeric types<\/strong>:<\/p>\n\n- Int (whole numbers)<\/li>\n
- Double (decimals \u2013 most common for real-world math)<\/li>\n
- Float (less common)<\/li>\n
- Decimal (exact decimals \u2013 used for money)<\/li>\n<\/ul>\n
2. Basic Arithmetic Operators \u2013 with examples<\/h3>\n\n
\n
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Swift<\/div>\n
\n
let a = 20\r\nlet b = 7\r\n\r\nprint(a + b) \/\/ 27\r\nprint(a - b) \/\/ 13\r\nprint(a * b) \/\/ 140\r\nprint(a \/ b) \/\/ 2 \u2190 integer division \u2192 drops the decimal part\r\nprint(a % b) \/\/ 6 \u2190 remainder after division<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\nImportant difference when using floating-point numbers:<\/strong><\/p>\n\n
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Swift<\/div>\n
\n
let x = 20.0\r\nlet y = 7.0\r\n\r\nprint(x + y) \/\/ 27.0\r\nprint(x - y) \/\/ 13.0\r\nprint(x * y) \/\/ 140.0\r\nprint(x \/ y) \/\/ 2.857142857142857 \u2190 keeps decimals\r\nprint(x.truncatingRemainder(dividingBy: y)) \/\/ 6.0<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\nRealistic example \u2013 price calculation<\/strong><\/p>\n\n
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Swift<\/div>\n
\n
let basePrice: Double = 1499.99\r\nlet quantity = 3\r\nlet taxRate: Double = 0.18\r\n\r\nlet subtotal = basePrice * Double(quantity) \/\/ 4499.97\r\nlet taxAmount = subtotal * taxRate \/\/ 809.9946\r\nlet finalAmount = subtotal + taxAmount \/\/ 5309.9646\r\n\r\nprint(\"Final price: \u20b9\\(finalAmount)\") \/\/ Final price: \u20b95309.9646<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n3. Compound Assignment Operators \u2013 very common shorthand<\/h3>\n
These combine an operation with assignment.<\/p>\n
\n
\n
\n
Swift<\/div>\n
\n
var score = 150\r\n\r\nscore += 100 \/\/ score = score + 100 \u2192 250\r\nscore -= 50 \/\/ \u2192 200\r\nscore *= 2 \/\/ \u2192 400\r\nscore \/= 4 \/\/ \u2192 100\r\nscore %= 7 \/\/ \u2192 2 (remainder after 100 \u00f7 7)\r\n\r\nprint(score) \/\/ 2<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\nReal-life pattern \u2013 accumulating totals<\/strong><\/p>\n\n
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Swift<\/div>\n
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var cartTotal: Decimal = 0\r\n\r\ncartTotal += 1499.99 \/\/ phone\r\ncartTotal += 899.00 \/\/ case\r\ncartTotal += 299.50 \/\/ screen protector\r\n\r\ncartTotal += cartTotal * 0.18 \/\/ add 18% GST\r\n\r\nprint(\"Cart total with tax: \u20b9\\(cartTotal)\")<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n4. Unary Minus Operator \u2013 changing sign<\/h3>\n\n
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Swift<\/div>\n
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let positive = 42\r\nlet negative = -positive \/\/ -42\r\n\r\nvar temperature = 36.6\r\ntemperature = -temperature \/\/ -36.6\r\n\r\nlet debt = -5000.75\r\nprint(debt) \/\/ -5000.75<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\nVery common use case \u2013 reversing direction<\/strong><\/p>\n\n
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Swift<\/div>\n
\n
var velocity = 50.0 \/\/ moving right\r\nvelocity = -velocity \/\/ now moving left<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n5. Increment \/ Decrement Operators \u2013 ++ and —<\/h3>\n
These exist in Swift, but they are very rarely used<\/strong> in modern code.<\/p>\n\n
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Swift<\/div>\n
\n
var count = 0\r\n\r\ncount += 1 \/\/ preferred style\r\ncount += 1\r\n\r\n\/\/ Old style (still works, but most developers avoid it now)\r\ncount++ \/\/ postfix \u2013 returns old value, then increments\r\n++count \/\/ prefix \u2013 increments first, then returns new value<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\nModern & clearer way (what you\u2019ll see in real code 2024\u20132026):<\/strong><\/p>\n\n
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Swift<\/div>\n
\n
var index = 0\r\n\r\nfor _ in 1...5 {\r\n index += 1\r\n print(\"Item \\(index)\")\r\n}<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\nWhy ++ and — are avoided in modern Swift:<\/strong><\/p>\n\n- They can make code harder to read<\/li>\n
- They behave differently depending on prefix\/postfix<\/li>\n
- += 1 is clearer and safer<\/li>\n<\/ul>\n
6. Arithmetic with Decimal \u2013 very important for money<\/h3>\n\n
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Swift<\/div>\n
\n
import Foundation\r\n\r\nlet coffeePrice: Decimal = 149.50\r\nlet quantity = 4\r\nlet discountPercent: Decimal = 10\r\n\r\nvar total = coffeePrice * Decimal(quantity) \/\/ 598.00\r\nlet discountAmount = total * (discountPercent \/ 100) \/\/ 59.80\r\ntotal -= discountAmount \/\/ 538.20\r\n\r\nlet gst = total * 0.18 \/\/ 96.876\r\ntotal += gst \/\/ 635.076\r\n\r\nprint(\"Final bill: \u20b9\\(total)\") \/\/ Final bill: \u20b9635.076<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\nImportant note:<\/strong><\/p>\n\n- Never do money math with Double \u2192 floating-point errors<\/li>\n
- Always use Decimal for currency<\/li>\n<\/ul>\n
7. Very Common Beginner Mistakes & Correct Habits<\/h3>\n\n
\n
\n\n\n| Mistake<\/th>\n | Wrong \/ Dangerous code<\/th>\n | Correct \/ Better habit<\/th>\n | Why?<\/th>\n<\/tr>\n<\/thead>\n |
\n\n| Doing money math with Double<\/td>\n | total += 0.1 many times<\/td>\n | Use Decimal for prices<\/td>\n | Avoids 0.30000000000000004 bugs<\/td>\n<\/tr>\n |
\n| Using \/ with Int and expecting decimals<\/td>\n | 10 \/ 3 \u2192 3<\/td>\n | 10.0 \/ 3.0 or Double(10) \/ 3<\/td>\n | Integer division truncates<\/td>\n<\/tr>\n |
\n| Writing x++ in complex expressions<\/td>\n | array[x++]<\/td>\n | array[x]; x += 1<\/td>\n | Much clearer, avoids bugs<\/td>\n<\/tr>\n |
\n| Forgetting to convert types<\/td>\n | price * quantity where quantity is Int<\/td>\n | price * Decimal(quantity)<\/td>\n | Prevents type mismatch<\/td>\n<\/tr>\n |
\n| Using % with negative numbers carelessly<\/td>\n | -10 % 3<\/td>\n | Be aware: Swift gives positive remainder<\/td>\n | -10 % 3 == 2 in Swift<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n 8. Quick Reference \u2013 Arithmetic Operators Cheat Sheet<\/h3>\n\n \n \n\n\n| Operator<\/th>\n | Meaning<\/th>\n | Example<\/th>\n | Result<\/th>\n | Most common real use<\/th>\n<\/tr>\n<\/thead>\n | \n\n| +<\/td>\n | Addition<\/td>\n | a + b<\/td>\n | sum<\/td>\n | Totals, concatenating strings<\/td>\n<\/tr>\n | \n| –<\/td>\n | Subtraction<\/td>\n | a – b<\/td>\n | difference<\/td>\n | Discounts, differences<\/td>\n<\/tr>\n | \n| *<\/td>\n | Multiplication<\/td>\n | price * quantity<\/td>\n | product<\/td>\n | Subtotal, scaling<\/td>\n<\/tr>\n | \n| \/<\/td>\n | Division<\/td>\n | total \/ count<\/td>\n | quotient<\/td>\n | Average, splitting amounts<\/td>\n<\/tr>\n | \n| %<\/td>\n | Remainder (modulo)<\/td>\n | value % 2<\/td>\n | remainder<\/td>\n | Checking even\/odd, cycling values<\/td>\n<\/tr>\n | \n| += -= *= \/= %=<\/td>\n | Compound assignment<\/td>\n | score += 100<\/td>\n | update<\/td>\n | Accumulating scores, totals, counters<\/td>\n<\/tr>\n | \n| – (unary)<\/td>\n | Negation<\/td>\n | -value<\/td>\n | negative<\/td>\n | Reverse direction, debt<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n 9. Small Practice \u2013 Try these now<\/h3>\n\n- Calculate final price: base price = 2499.99 quantity = 2 discount = 20% GST = 18% \u2192 what is the final amount?<\/li>\n
- Check if a number is divisible by 5 let number = 125 \u2192 use % and print “Divisible” or “Not divisible”<\/li>\n
- Update a counter every time an item is added to cart var itemCount = 0 \u2192 add 3 items, then add 2 more<\/li>\n<\/ol>\n
Paste your attempts if you want feedback!<\/p>\n What would you like to explore next?<\/p>\n \n- Arithmetic with Decimal<\/strong> in more detail (money examples)<\/li>\n
- How to avoid floating-point surprises<\/strong><\/li>\n
- Rounding<\/strong> numbers (round, ceil, floor)<\/li>\n
- Random numbers<\/strong> (Int.random(in:), Double.random(in:))<\/li>\n
- Or move to another group of operators (comparison, logical, range\u2026)<\/li>\n<\/ul>\n
Just tell me \u2014 we\u2019ll continue in the same detailed, patient, teacher-like style \ud83d\ude0a<\/p>\n","protected":false},"excerpt":{"rendered":" 1. What are Arithmetic Operators? Arithmetic operators are the mathematical symbols you use to perform calculations: + addition – subtraction * multiplication \/ division % remainder (modulo) These operators work with numeric types: Int...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[76],"tags":[],"class_list":["post-2632","post","type-post","status-publish","format-standard","hentry","category-swift"],"_links":{"self":[{"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/posts\/2632","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/comments?post=2632"}],"version-history":[{"count":1,"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/posts\/2632\/revisions"}],"predecessor-version":[{"id":2633,"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/posts\/2632\/revisions\/2633"}],"wp:attachment":[{"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/media?parent=2632"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/categories?post=2632"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/demo.materiamedica.net\/demo6\/wp-json\/wp\/v2\/tags?post=2632"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} | |