WEBVTT 1 00:00:00.120 --> 00:00:02.240 For many of us in software development, the way we 2 00:00:02.279 --> 00:00:05.799 build systems is constantly evolving. It's not just about adopting 3 00:00:05.799 --> 00:00:09.839 a new tool, it's about shifting our fundamental approach. You know, 4 00:00:10.359 --> 00:00:16.199 how we tackle complex problems like concurrency, fault tolerance, maintainability. Today, 5 00:00:16.239 --> 00:00:19.120 we're taking a deep dive into just such a powerful paradigm, 6 00:00:19.640 --> 00:00:23.679 functional programming, and we're using Elixer as our expert guide. 7 00:00:23.839 --> 00:00:26.600 We're inviting you to explore a different mindset, one that 8 00:00:26.640 --> 00:00:29.440 offers a really fresh and powerful perspective on how you 9 00:00:29.480 --> 00:00:31.239 approach development exactly. 10 00:00:31.640 --> 00:00:34.200 Our mission for this deep dive is well to lay 11 00:00:34.200 --> 00:00:38.479 out the essence of functional programming, explore wides become increasingly 12 00:00:38.520 --> 00:00:42.439 important in modern software, and demonstrate how Elixer serves as 13 00:00:42.479 --> 00:00:45.280 just a fantastic vehicle for exploring this style. And even 14 00:00:45.280 --> 00:00:47.399 if you don't switch to Alizer for your next project, 15 00:00:47.520 --> 00:00:50.479 you'll uncover concepts here, concepts that are already supported in 16 00:00:50.520 --> 00:00:54.520 many mainstream languages, hopefully providing those aha moments they quickly 17 00:00:54.560 --> 00:00:55.520 deepen your understanding. 18 00:00:55.600 --> 00:00:58.799 Okay, let's unpack this, then, what's the fundamental shift in 19 00:00:58.880 --> 00:01:02.439 thinking for functional program It really is a different mindset 20 00:01:02.520 --> 00:01:04.959 from what many of us are used to. Right. 21 00:01:05.480 --> 00:01:08.159 Yeah. The core idea is that functional programming is a 22 00:01:08.200 --> 00:01:12.319 distinct paradigm. It moves away from explicit, step by step instructions. 23 00:01:12.760 --> 00:01:15.319 So instead of focusing on how to achieve a result 24 00:01:15.560 --> 00:01:18.480 through a sequence of changing states, we describe what the 25 00:01:18.519 --> 00:01:22.000 software must do. We build systems by composing functions that 26 00:01:22.040 --> 00:01:23.159 transform data. 27 00:01:23.200 --> 00:01:25.640 And a cornerstone of this paradigm, I hear, is something 28 00:01:25.680 --> 00:01:29.200 called immutability. Now, for those of us accustomed to directly 29 00:01:29.280 --> 00:01:32.680 changing data, how does that work? And maybe more importantly, 30 00:01:32.719 --> 00:01:35.239 why is it such a game changer, especially for something 31 00:01:35.280 --> 00:01:36.159 like parallelism. 32 00:01:36.719 --> 00:01:40.599 Right, So, conventional languages often rely on mutating shared values, 33 00:01:40.920 --> 00:01:45.439 which then requires complex mechanisms you know, locks semaphores to 34 00:01:45.519 --> 00:01:49.200 prevent raise conditions when you're working concurrently. The profound impact 35 00:01:49.280 --> 00:01:53.120 of immutability in functional programming is that all values, once created, 36 00:01:53.280 --> 00:01:57.159 cannot be changed. Ever, this means each function operates on 37 00:01:57.200 --> 00:02:00.400 a stable input, which eliminates the need for those intricate 38 00:02:00.439 --> 00:02:04.439 lock mechanisms and drastically simplifies concurrent and parallel work. 39 00:02:04.519 --> 00:02:06.879 Okay, but doesn't creating new values all the time slow 40 00:02:06.920 --> 00:02:07.439 things down? 41 00:02:07.680 --> 00:02:10.759 That's a common thought. Yeah, But languages like Elixir use 42 00:02:10.800 --> 00:02:15.639 smart immutable data structures, they efficiently reuse memory behind the scenes. So, 43 00:02:15.680 --> 00:02:17.919 for example, if you have a list like one, two, three, four, 44 00:02:18.680 --> 00:02:21.800 and you call say list dot delaty, list manage one, 45 00:02:21.919 --> 00:02:25.319 or list plus plus one the original list value that one, two, 46 00:02:25.360 --> 00:02:28.800 three four, it stays exactly the same. These operations produce 47 00:02:28.879 --> 00:02:32.240 new lists, and because the original data is untouched, the 48 00:02:32.280 --> 00:02:35.639 compiler can safely run these operations in parallel without worrying 49 00:02:35.639 --> 00:02:37.159 about side effects messing with the input. 50 00:02:37.280 --> 00:02:40.879 Okay, okay, So if data is immutable, what then becomes 51 00:02:41.319 --> 00:02:44.719 the primary building block, the star of the show? So 52 00:02:44.759 --> 00:02:47.960 to speak? How are functions themselves different here than what 53 00:02:47.960 --> 00:02:51.080 we might be used to in, say, oh languages. 54 00:02:50.680 --> 00:02:54.639 Great question. In functional programming, functions are first class citizens, 55 00:02:55.360 --> 00:02:57.879 which means they're treated just like any other value. You 56 00:02:57.919 --> 00:03:00.400 can assign them to variables, pass them as our arguments 57 00:03:00.400 --> 00:03:02.560 to other functions, even return them from other functions. What 58 00:03:02.800 --> 00:03:07.719 data exactly like data? They explicitly receive input, process it, 59 00:03:07.960 --> 00:03:10.639 and return output. Now, if you use to an object 60 00:03:10.719 --> 00:03:14.599 oriented approach, where operations are methods tied to an object's 61 00:03:14.639 --> 00:03:19.919 changing state, functional programming offers an alternative. Operations exist independently. 62 00:03:20.159 --> 00:03:23.000 You send the data to the function. A classic example 63 00:03:23.039 --> 00:03:26.960 is something like enom dot map dogs, cats, flowers and 64 00:03:27.000 --> 00:03:29.800 strained out up case one. Here we're passing the string 65 00:03:29.840 --> 00:03:33.159 dot upcase function itself as an argument to transform each 66 00:03:33.240 --> 00:03:33.800 item in the. 67 00:03:33.759 --> 00:03:36.680 List that brings us to a key distinction. Then the 68 00:03:36.719 --> 00:03:40.159 difference between a pure function and an impure one. Why 69 00:03:40.199 --> 00:03:43.360 does that distinction matter so much for predictability, especially when 70 00:03:43.400 --> 00:03:44.680 we're trying to reason about our code. 71 00:03:44.879 --> 00:03:48.639 Ah purity. Yes, pure functions are incredibly predictable. Given the 72 00:03:48.680 --> 00:03:51.360 exact same input, they will always produce the same consistent 73 00:03:51.400 --> 00:03:55.280 output always, and critically, they have no observable effects outside 74 00:03:55.280 --> 00:03:57.879 of their own scope, no side effects. This is often 75 00:03:57.919 --> 00:03:59.400 called referential transparency. 76 00:03:59.639 --> 00:04:03.159 Like a mathematical function, pretty much, take ad two op 77 00:04:03.280 --> 00:04:06.439 l nabn plus two N. If you call add two 78 00:04:06.479 --> 00:04:09.599 o two, you will always get four every single time, 79 00:04:09.840 --> 00:04:13.080 no surprises. And the real aha here isn't just the 80 00:04:13.120 --> 00:04:18.040 predictability itself, it's the profound impact on debugging. Imagine finding 81 00:04:18.079 --> 00:04:21.279 a bug with pure functions, you can isolate the problem 82 00:04:21.319 --> 00:04:23.920 to a single function call you know it won't be 83 00:04:23.920 --> 00:04:27.680 affected by hidden system state or alter anything outside his control. 84 00:04:28.120 --> 00:04:31.639 It transforms debugging from this complex detective hunt into a 85 00:04:31.720 --> 00:04:33.439 much more straightforward analysis. 86 00:04:33.639 --> 00:04:35.720 Okay, so what about impure functions then. 87 00:04:35.680 --> 00:04:38.720 Well, impure functions are the unpredictable ones. They might return 88 00:04:38.759 --> 00:04:41.319 different results for the same input, or they produce side 89 00:04:41.319 --> 00:04:44.519 effects by interacting with the outside world. Think about reading 90 00:04:44.639 --> 00:04:47.800 user input from the terminal like io dot gets what's 91 00:04:47.839 --> 00:04:50.040 the meaning of life that depends on the user, or 92 00:04:50.079 --> 00:04:54.839 getting the current time daytime dot uacat now that changes constantly. 93 00:04:55.160 --> 00:04:58.040 They're absolutely necessary for any useful software. Of course, you 94 00:04:58.079 --> 00:05:00.240 need to interact with the world, but the key is 95 00:05:00.240 --> 00:05:03.680 to isolate these impure parts, handle them carefully, often at 96 00:05:03.680 --> 00:05:05.480 the edges of your application. 97 00:05:05.160 --> 00:05:07.680 So pushing the messy stuff to the boundaries. 98 00:05:07.439 --> 00:05:09.879 Kind of yeah, containing the unpredictability. 99 00:05:10.040 --> 00:05:12.360 So what does this all mean for how we actually 100 00:05:12.399 --> 00:05:16.120 write the code? Does it lead to a completely different style? 101 00:05:16.639 --> 00:05:19.959 It definitely fosters a declarative style of programming. You focus 102 00:05:19.959 --> 00:05:22.639 on what needs to be done, rather than explicitly defining 103 00:05:22.680 --> 00:05:25.480 how to do it step by step. This contrast pretty 104 00:05:25.480 --> 00:05:29.480 sharply with an imperative approach. Consider transforming a list of 105 00:05:29.480 --> 00:05:32.879 strings to uppercase. An imperative JavaScript example might use a 106 00:05:32.920 --> 00:05:36.639 for loop manually incrementing e, pushing results to a new 107 00:05:36.720 --> 00:05:39.160 array that gets verbose. 108 00:05:39.319 --> 00:05:40.360 Yeah, I can picture that. 109 00:05:40.879 --> 00:05:44.319 In Alixir using a declarative style, you might use recursion, 110 00:05:44.360 --> 00:05:46.839 which we'll talk about yeah, or more commonly, a higher 111 00:05:46.920 --> 00:05:50.639 order function like enom dot map in string dot case one. 112 00:05:51.040 --> 00:05:53.759 This approach makes the crucial aspects of the task, the 113 00:05:53.759 --> 00:05:57.439 parts that really matter, explicit, and it often generates much simpler, 114 00:05:57.519 --> 00:05:58.399 more readable code. 115 00:05:58.600 --> 00:06:01.079 Okay, that makes sense. Now let's turn our attention to 116 00:06:01.120 --> 00:06:04.879 Elixir itself. How does Elixer enable this functional way of thinking? 117 00:06:04.959 --> 00:06:06.120 Right from its foundations? 118 00:06:06.399 --> 00:06:09.879 Right? So, Elixer is a dynamic functional programming language. It's 119 00:06:09.879 --> 00:06:12.680 built on the erline VM beam, which is renowned for 120 00:06:12.680 --> 00:06:17.519 its capabilities in building distributed fault tolerant systems rock solid foundation. 121 00:06:18.439 --> 00:06:21.639 Elixer was designed to offer a modern kind of fun syntax, 122 00:06:21.879 --> 00:06:25.759 a vibrant community, and really robust production ready tooling. You 123 00:06:25.800 --> 00:06:28.600 can interact with it in an interactive shell called IIx, 124 00:06:28.680 --> 00:06:32.000 which is great for experimenting, or you compile dot e's 125 00:06:32.040 --> 00:06:35.199 files for larger projects, or run dot x or scripts 126 00:06:35.199 --> 00:06:41.879 for quick tasks. Elissa's basic types include integers, strings, booleans, atoms, lists, tuples, 127 00:06:41.920 --> 00:06:44.959 and even functions themselves. As we said, operators work mostly 128 00:06:45.000 --> 00:06:48.680 as you'd expect for arithmetic, plus IDs and comparisons, and 129 00:06:48.800 --> 00:06:51.360 invalid expressions like trying to add a string in a 130 00:06:51.439 --> 00:06:55.079 number will predictably fail with clear errors, no silent failures. 131 00:06:55.160 --> 00:06:57.800 Good Now, Variables and Elixir function a bit differently than 132 00:06:57.839 --> 00:07:00.519 in many other languages. When you write X equal forty two, 133 00:07:00.560 --> 00:07:03.759 you're performing binding. The operator binds the value forty two 134 00:07:03.759 --> 00:07:06.319 to the name X. But what's crucial time back to 135 00:07:06.360 --> 00:07:09.439 immutability is that values are immutable. So if you later 136 00:07:09.439 --> 00:07:10.879 write xquel six. 137 00:07:10.639 --> 00:07:12.360 You're not changing the forty two exactly. 138 00:07:12.920 --> 00:07:15.639 You're not changing the original forty two in memory. You're 139 00:07:15.639 --> 00:07:18.160 simply rebinding the name X to point to a new 140 00:07:18.199 --> 00:07:21.240 value six. The old forty two might still be referenced 141 00:07:21.279 --> 00:07:24.839 elsewhere or get garbage collected later. This prevents those accidental 142 00:07:24.839 --> 00:07:27.920 side effects and makes reasoning about your code much much simpler, 143 00:07:28.240 --> 00:07:31.040 because you know of value once bound won't just change 144 00:07:31.040 --> 00:07:34.000 out from under you unexpectedly, and it's good practice to 145 00:07:34.079 --> 00:07:37.360 use descriptive snake case names like total cost rather than 146 00:07:37.480 --> 00:07:41.079 just x or y helps clarity. Oh, and remember variables 147 00:07:41.120 --> 00:07:43.759 starting with capital letters or deserved for modules or atoms. 148 00:07:43.959 --> 00:07:46.720 Got it. Anonymous functions are also essential to Elixir. These 149 00:07:46.720 --> 00:07:49.439 are functions without a global name, typically created on the fly. 150 00:07:50.199 --> 00:07:51.879 You often bind them to a variable if you want 151 00:07:51.879 --> 00:07:55.240 to reuse them. The syntax is sn parameter is body 152 00:07:55.319 --> 00:07:59.600 end for instance sn name ss HeLa hashtag name dot 153 00:07:59.759 --> 00:08:02.439 end simple enough. You then invoke it using a dot 154 00:08:02.720 --> 00:08:06.439 helo and they can be multiling take multiple arguments. Very flexible, 155 00:08:07.319 --> 00:08:09.800 and this flexibility leads us to an important concept. How 156 00:08:09.879 --> 00:08:12.639 values are shared with these functions, even without being explicitly 157 00:08:12.639 --> 00:08:15.040 passed as arguments, which brings us to closures. 158 00:08:15.279 --> 00:08:18.319 Right, you mentioned closures earlier. It sounds a bit abstract. 159 00:08:18.759 --> 00:08:21.399 How do they actually help us share values in a 160 00:08:21.439 --> 00:08:24.759 way we can't otherwise control. What's the practical benefit here? 161 00:08:24.839 --> 00:08:28.199 Okay? Think of a closure like this. When you create 162 00:08:28.240 --> 00:08:32.360 an anonymous function, it takes all the variables that are 163 00:08:32.399 --> 00:08:35.799 currently visible in its surrounding environment and it puts them 164 00:08:35.799 --> 00:08:39.240 into its own little backpack. No matter where that function 165 00:08:39.399 --> 00:08:41.879 goes or when it gets called later, even in a 166 00:08:41.919 --> 00:08:45.000 completely different process, it always carries that backpack with its 167 00:08:45.000 --> 00:08:46.200 remembered values. 168 00:08:45.919 --> 00:08:48.159 So it closes over the environment it was born in. 169 00:08:48.440 --> 00:08:52.639 Exactly. A closure is an anonymous function that remembers values 170 00:08:52.679 --> 00:08:55.960 from its lexical scope, that specific block of code where 171 00:08:56.000 --> 00:08:58.559 it was defined, even if it's executed much later or 172 00:08:58.559 --> 00:09:01.919 somewhere else entirely. This is super useful when you're working 173 00:09:01.919 --> 00:09:04.879 with functions that take other functions as arguments, like an 174 00:09:05.000 --> 00:09:09.360 ENEM dot map sometimes or quickly when starting asynchronous processes 175 00:09:09.360 --> 00:09:12.279 where you can't explicitly pass arguments in the traditional way. 176 00:09:12.559 --> 00:09:16.080 For example, if you define message hello world outside and 177 00:09:16.080 --> 00:09:19.919 then salo fna a l process dot sleep one thousand 178 00:09:20.559 --> 00:09:24.919 eiotut's message end, that SALEO function will remember the message 179 00:09:24.960 --> 00:09:27.600 value even when you run it asynchronously in a separate 180 00:09:27.639 --> 00:09:31.919 process using spawn salo, the innfunction can see variables defined 181 00:09:31.919 --> 00:09:34.799 outside its immediate body. It's a powerful way to handle 182 00:09:34.799 --> 00:09:36.559 state without needing explicit objects. 183 00:09:36.600 --> 00:09:39.440 Sometimes that's pretty cool. Okay, now that we've covered the basics, 184 00:09:39.480 --> 00:09:42.519 Elixir has some truly powerful features that make functional programming 185 00:09:42.559 --> 00:09:46.039 really sing. Let's talk about organizing code and some very 186 00:09:46.080 --> 00:09:48.159 clever ways to control program flow. 187 00:09:48.440 --> 00:09:48.639 Yeah. 188 00:09:48.679 --> 00:09:53.759 Absolutely. For larger, more organized applications, Elixir uses named functions. 189 00:09:54.080 --> 00:09:57.360 These are defined inside modules using deaf module and DEAF 190 00:09:57.720 --> 00:10:02.279 standard stuff. For organization modules help structure your code logically, 191 00:10:02.799 --> 00:10:05.440 and you can test them using namespaces like e commerce 192 00:10:06.120 --> 00:10:09.480 check out for better organization as things grow. Functions within 193 00:10:09.519 --> 00:10:12.600 a module can also be made private using death that 194 00:10:12.639 --> 00:10:14.799 restricts their access just to within that module. 195 00:10:15.000 --> 00:10:17.120 Good encapsulation and importing functions. 196 00:10:17.279 --> 00:10:20.279 You can import functions from other modules for brevity, sure, 197 00:10:20.519 --> 00:10:23.919 but many Elixer developers actually prefer explicitly calling module name 198 00:10:24.000 --> 00:10:27.039 dot function. It keeps the code really clear, but exactly 199 00:10:27.039 --> 00:10:30.399 where each function is coming from less magic, and what's 200 00:10:30.440 --> 00:10:32.559 need is you can treat these name functions as values 201 00:10:32.600 --> 00:10:36.720 themselves using the function capturing operator. The ampersand for instance, 202 00:10:36.759 --> 00:10:40.039 factorial am equals and factorial dot f one captures a 203 00:10:40.080 --> 00:10:42.799 reference to the factorial dot f function that takes one 204 00:10:42.879 --> 00:10:45.879 argument that's the one. This lets you pass named functions 205 00:10:45.879 --> 00:10:48.399 around just like any other value, slotting them into places 206 00:10:48.440 --> 00:10:50.879 expecting an anonymous function. It's quite elegant, okay. 207 00:10:50.919 --> 00:10:53.919 That brings us to a really innovative approach Elixer takes 208 00:10:53.960 --> 00:10:57.360 to controlling program flow. You mentioned the equals sign. It 209 00:10:57.440 --> 00:10:59.639 changes how you think about entirely, doesn't it. 210 00:10:59.639 --> 00:11:03.159 It really does? So how do we control program flow effectively? 211 00:11:03.200 --> 00:11:07.559 Without mutable state and traditional loops. The answer in large 212 00:11:07.559 --> 00:11:11.080 part is pattern matching. It's absolutely central to Elixir. The 213 00:11:11.120 --> 00:11:14.559 operator isn't just for assignment like in many languages, it's 214 00:11:14.600 --> 00:11:18.559 actually the match operator. It attempts to make both sides equivalent. 215 00:11:18.840 --> 00:11:22.320 So one nixel one matches. That succeeds, but two equals 216 00:11:22.360 --> 00:11:23.840 one fails. It throws a. 217 00:11:23.799 --> 00:11:26.360 Matcher because they aren't equivalent right now. 218 00:11:26.360 --> 00:11:28.200 When you use a variable on the left like x 219 00:11:28.279 --> 00:11:31.360 isn't bound. It binds value one to X. That looks 220 00:11:31.399 --> 00:11:33.759 like assignment. But if x already has a value, say 221 00:11:33.879 --> 00:11:36.399 x's two, then two x would succeed because they match, 222 00:11:36.480 --> 00:11:38.720 but three xles would fail with a matcher. It's not 223 00:11:38.799 --> 00:11:42.200 reassignment in that context. It's an assertion of equality. And 224 00:11:42.240 --> 00:11:45.399 you can use the pin operator like percent strength value 225 00:11:45.600 --> 00:11:48.480 to force elixer to use the current value of strength 226 00:11:48.559 --> 00:11:50.679 value for matching rather than trying to rebind. 227 00:11:50.679 --> 00:11:53.200 It useful to prevent accidental rebinding. 228 00:11:52.840 --> 00:11:56.559 Within a match exactly, and pattern matching is incredibly powerful 229 00:11:56.639 --> 00:12:00.000 for destructuring two. That means pulling values out of complay 230 00:12:00.200 --> 00:12:03.480 data types like two poles okay, answer okay, this bind's 231 00:12:03.519 --> 00:12:06.879 forty two to answer or lists headtail, one two three. 232 00:12:07.120 --> 00:12:09.320 This binds one to head and two to three to tail. 233 00:12:09.759 --> 00:12:12.879 Super common for recursion maps. Done percent strength and strength 234 00:12:12.919 --> 00:12:15.919 valuabilities pulls out the value associated with the strength key 235 00:12:16.440 --> 00:12:19.600 and strucks work. Similarly, you can also use a wildcard 236 00:12:19.679 --> 00:12:21.480 to ignore parts of a match you don't need. 237 00:12:21.840 --> 00:12:24.759 Wow, Okay, that's a lot packed into the sign it. 238 00:12:24.679 --> 00:12:28.200 Is and building directly on pattern matching, Elixer uses function 239 00:12:28.320 --> 00:12:31.759 clauses as a primary way to control program flow. You 240 00:12:31.759 --> 00:12:34.159 can find multiple functions with the same name but with 241 00:12:34.200 --> 00:12:38.080 different argument patterns. ELSTA will then automatically execute the first 242 00:12:38.080 --> 00:12:41.799 function clause whose arguments successfully match the incoming values when 243 00:12:41.799 --> 00:12:42.240 you call it. 244 00:12:42.600 --> 00:12:45.080 So instead of a big IFL sort switch. 245 00:12:44.799 --> 00:12:47.879 Inside the function, you just define different function bodies for 246 00:12:47.919 --> 00:12:52.039 different input shapes. It's very declarative. For example, a number 247 00:12:52.080 --> 00:12:55.639 compared dot greater function might internally call different check clauses 248 00:12:55.679 --> 00:12:59.960 based on a comparison. Maybe check true number handles the 249 00:13:00.080 --> 00:13:02.720 case where the first number is greater, and check false 250 00:13:03.080 --> 00:13:05.559 other number handles the case where the second is greater. 251 00:13:05.960 --> 00:13:09.279 Each check clause only matches its specific scenario, and to 252 00:13:09.279 --> 00:13:12.639 add even more power, you have guard clauses. See these 253 00:13:12.759 --> 00:13:15.559 use the when keyword right after the function definition to 254 00:13:15.600 --> 00:13:19.840 add boolean checks like def greater number other number when 255 00:13:19.919 --> 00:13:23.320 number or the other number two number. This clause only 256 00:13:23.360 --> 00:13:26.159 matches if number is actually greater than or equal to 257 00:13:26.240 --> 00:13:30.320 other number. Guards are incredibly useful for enforcing conditions or types, 258 00:13:30.639 --> 00:13:33.279 like when price equals zero and tax rate equals zero. 259 00:13:33.399 --> 00:13:36.000 It often reduces the need for nested if statements are 260 00:13:36.039 --> 00:13:39.879 separate helper functions. Just note only pure and generally fast 261 00:13:39.919 --> 00:13:43.000 functions are allowed inside guard clauses to keep them efficient 262 00:13:43.000 --> 00:13:43.679 and predictable. 263 00:13:43.799 --> 00:13:47.080 That's really elegant. Okay, so repetition, that's fundamental in programming. 264 00:13:47.200 --> 00:13:49.799 But if we're avoiding traditional loops, how do we repeat 265 00:13:49.799 --> 00:13:51.480 tasks in a purely functional way. 266 00:13:51.840 --> 00:13:55.720 Recursion? That's the core mechanism. A recursive function is simply 267 00:13:55.759 --> 00:13:59.000 one that calls itself repeatedly. The crucial part is that 268 00:13:59.039 --> 00:14:01.679 it must have a stop condition or boundary clause a 269 00:14:01.720 --> 00:14:04.159 base case, to prevent it from looping forever. 270 00:14:04.240 --> 00:14:06.039 Yeah, it got to stop somewhere exactly. 271 00:14:06.320 --> 00:14:08.840 Take SMIng numbers up to n. The base case is 272 00:14:08.840 --> 00:14:10.840 some dot up two m it, which is just zero, 273 00:14:11.080 --> 00:14:12.879 and then some dot up to mber for any other 274 00:14:13.000 --> 00:14:15.000 n is n plus some dot up to n one. 275 00:14:15.399 --> 00:14:18.000 See how each call reduces the problem and one until 276 00:14:18.000 --> 00:14:21.120 it hits the base case zero. The same principle applies 277 00:14:21.159 --> 00:14:24.000 to complex tasks like navigating lists. You might sum a 278 00:14:24.000 --> 00:14:27.080 list using some headtail, which calculates head plus some tail 279 00:14:27.279 --> 00:14:29.679 until you hit the empty lisk mware where some return 280 00:14:29.840 --> 00:14:31.039 zero the base again. 281 00:14:31.240 --> 00:14:33.240 So you process one element and recurse on. 282 00:14:33.240 --> 00:14:38.440 The rest precisely, and two common recursive patterns emerge. Decrease 283 00:14:38.480 --> 00:14:42.039 and conquer simplifies the problem incrementally down to the base case, 284 00:14:42.320 --> 00:14:45.840 then builds the solution back up. Factorial is a classic example. 285 00:14:46.039 --> 00:14:49.639 Factorial dot fFN is n an factorial dom n one 286 00:14:49.720 --> 00:14:52.240 until you hit factorial dot of zero, which is one. 287 00:14:52.679 --> 00:14:55.519 Then there's divideing Concker. This splits the problem in a 288 00:14:55.559 --> 00:14:59.759 smaller independent subproblems, solves those recursively, and then combines the 289 00:14:59.799 --> 00:15:03.440 res the famous merge sort algorithm for lists. It's a 290 00:15:03.440 --> 00:15:05.799 perfect example. You keep splitting the list until you have 291 00:15:05.879 --> 00:15:08.279 lists of one element which are inherently sorted. Then you 292 00:15:08.360 --> 00:15:10.240 merge them back together in sorted order. 293 00:15:10.720 --> 00:15:15.600 That sounds incredibly powerful for handling tasks iteratively. But wait, 294 00:15:15.960 --> 00:15:18.799 with all these function calls stacking up. Doesn't recursion just 295 00:15:18.879 --> 00:15:21.440 gobble up memory on the call stack? Isn't that a problem? 296 00:15:21.480 --> 00:15:23.320 Is there a trick to make it more memory efficient? 297 00:15:23.600 --> 00:15:26.279 That is a very perceptive question, and you're absolutely right. 298 00:15:26.360 --> 00:15:29.320 Now you've recursion can consume significant memory. It can lead 299 00:15:29.320 --> 00:15:33.279 to stack overflows for deep recursions. The crucial solution the 300 00:15:33.360 --> 00:15:38.039 trick is tail call optimization or TCO. Okay, So a 301 00:15:38.080 --> 00:15:41.360 body recursive function has its recursive call, but it's not 302 00:15:41.399 --> 00:15:43.879 the very last thing it does. Like our factorial dot 303 00:15:44.039 --> 00:15:48.600 nfactorialp fn one, there's still a multiplication after the recursive 304 00:15:48.639 --> 00:15:51.799 call returns. This means the intermediate results the context of 305 00:15:51.840 --> 00:15:53.759 each call have to be kept on the call stack 306 00:15:53.840 --> 00:15:58.120 stack grows A tail recursive function, however, performs a recursive 307 00:15:58.159 --> 00:16:01.120 call as its absolute final action. There's nothing left to 308 00:16:01.120 --> 00:16:04.840 do after it returns. Often this involves passing an accumulator 309 00:16:04.960 --> 00:16:07.879 argument to carry the state forward. So factorial might become 310 00:16:07.960 --> 00:16:11.120 factorial off n one n acc where aci holds the 311 00:16:11.120 --> 00:16:14.879 result calculated so far. The beauty is Elixir's compiler and 312 00:16:14.879 --> 00:16:18.039 the Erlang VM can optimize these tail recursive calls. It 313 00:16:18.080 --> 00:16:21.279 effectively transforms them into iterative loops under the hood like 314 00:16:21.320 --> 00:16:24.240 a go to. This results in constant low memory consumption, 315 00:16:24.360 --> 00:16:25.000 just like a loop. 316 00:16:25.200 --> 00:16:27.440 Wow, so tail recursion gets optimized away. 317 00:16:27.559 --> 00:16:31.080 Yes, it avoids growing the call stack. It's a trade off. 318 00:16:31.159 --> 00:16:34.440 Sometimes the tail recursive version might look slightly more complex 319 00:16:34.480 --> 00:16:37.480 to read initially, but the memory efficiency game is often 320 00:16:37.559 --> 00:16:42.000 essential for deep or potentially infinite recursions, which brings us 321 00:16:42.039 --> 00:16:43.600 to unbounded recursion. 322 00:16:43.960 --> 00:16:44.320 Yeah. 323 00:16:44.399 --> 00:16:47.000 Sometimes you can't predict the number of repetitions. Think of 324 00:16:47.039 --> 00:16:50.240 a web crawler following links or navigating a file system 325 00:16:50.279 --> 00:16:52.720 that might have circular references or symbolic links. 326 00:16:52.799 --> 00:16:54.120 Yeah, that could go on forever. 327 00:16:54.480 --> 00:16:58.360 Right, So strategies there include adding explicit boundaries like setting 328 00:16:58.399 --> 00:17:02.600 a maximum depth for direct navigation, or actively detecting and 329 00:17:02.639 --> 00:17:06.440 avoiding circular references, perhaps by keeping track of visited nodes 330 00:17:06.559 --> 00:17:09.319 or checking for symbolic links using something like file dot 331 00:17:09.440 --> 00:17:10.039 l stat one. 332 00:17:10.240 --> 00:17:12.839 Okay, makes sense. So how do we use these functional 333 00:17:12.839 --> 00:17:15.519 principles then, to abstract away the tedious stuff? How do 334 00:17:15.519 --> 00:17:18.880 we build those better functions with simple interfaces that developers 335 00:17:18.920 --> 00:17:19.960 actually enjoy using. 336 00:17:20.200 --> 00:17:23.759 This is where higher order functions or hos truly shine. 337 00:17:24.240 --> 00:17:26.680 Remember these are functions that either take other functions as 338 00:17:26.759 --> 00:17:30.680 arguments or they return functions, or maybe both. They are 339 00:17:30.680 --> 00:17:35.319 incredibly powerful for hiding verbose or laborious routines behind elegant 340 00:17:35.480 --> 00:17:39.960 simple interfaces. Think about file dot open three Intelixir takes 341 00:17:39.960 --> 00:17:42.440 a path, options, and a function to execute with the 342 00:17:42.480 --> 00:17:45.640 open file handle. The file dot open function handles opening 343 00:17:45.720 --> 00:17:48.880 the file, running your function, and crucially ensuring the file 344 00:17:48.960 --> 00:17:52.480 is closed afterwards even if errors occur. It abstracts away 345 00:17:52.519 --> 00:17:54.000 all that tricky resource. 346 00:17:53.640 --> 00:17:56.559 Management nice so it hides the boilerplate exactly. 347 00:17:56.799 --> 00:18:00.319 And common list operations are prime examples. Etam dot each 348 00:18:00.480 --> 00:18:02.920 takes a function and applies it to every item, just 349 00:18:02.960 --> 00:18:05.920 for side effects. Enom dot map takes a function, applies 350 00:18:05.920 --> 00:18:08.359 it to transform each item, and returns a new list 351 00:18:08.359 --> 00:18:11.960 of the results, like increasing prices. Enom dot reduce takes 352 00:18:11.960 --> 00:18:14.400 a function and an initial accumulator and boils a list 353 00:18:14.480 --> 00:18:18.160 down to a single value, like summing total income. Enom 354 00:18:18.160 --> 00:18:20.759 dot filter takes a function that returns truer falls and 355 00:18:20.799 --> 00:18:23.359 selects only the items for which it's true. These are 356 00:18:23.359 --> 00:18:26.480 all higher order functions found in Elixer's awesome Enom module, 357 00:18:26.799 --> 00:18:29.440 and the Enom functions work seamlessly with any data type 358 00:18:29.440 --> 00:18:34.079 that implements the innumerable protocol lists, maps, ranges, streams, incredibly 359 00:18:34.160 --> 00:18:37.039 versatile protocols. I'll get to those, we will an Elixer 360 00:18:37.079 --> 00:18:41.119 also provides comprehensions using the inneverrable inn acol for special form. 361 00:18:41.680 --> 00:18:44.680 It offers a concise, really readable fintax that often bundles 362 00:18:44.680 --> 00:18:47.880 common enom operations like iterating, mapping, and filtering into a 363 00:18:47.880 --> 00:18:50.240 single expressive statement. Very Python like. 364 00:18:50.279 --> 00:18:52.240 If you know that the four comprehensions make a lot 365 00:18:52.240 --> 00:18:55.240 of sense. Yeah, but the pipe operator. I hear about 366 00:18:55.279 --> 00:18:57.519 this a lot with Elixer. It seems like a standout feature. 367 00:18:57.640 --> 00:19:01.000 What's its superpower? What makes it so effective for code readability? 368 00:19:01.160 --> 00:19:01.319 Oh? 369 00:19:01.359 --> 00:19:05.920 The pipe operator? Yes, yes, it's arguably Elixer's most famous 370 00:19:05.920 --> 00:19:09.640 feature for transforming data. Its purpose is simple but profound. 371 00:19:10.119 --> 00:19:13.559 It makes combining function calls in sequence incredibly readable, almost 372 00:19:13.559 --> 00:19:17.119 like reading plain English. Its superpower is just this. It 373 00:19:17.160 --> 00:19:19.799 takes the result of the expression on its left and 374 00:19:19.880 --> 00:19:22.160 passes it as the first argument to the function on 375 00:19:22.200 --> 00:19:26.119 its right. That's it. So remember that example of capitalizing 376 00:19:26.119 --> 00:19:28.359 words in a title instead of a nested mess like 377 00:19:28.720 --> 00:19:31.480 enom dot join enom dot maps string dot capitalize one. 378 00:19:31.559 --> 00:19:31.759 Yeah. 379 00:19:31.799 --> 00:19:33.880 Hard to read inside out exactly. 380 00:19:33.400 --> 00:19:35.279 With the pipe. You write a clear left to right 381 00:19:35.319 --> 00:19:39.319 pipeline well title string dot, split enom dot, map, enom 382 00:19:39.319 --> 00:19:41.759 dot join. It reads like take the title, then split 383 00:19:41.799 --> 00:19:44.480 it the map, capitalize over it, then join it with spaces. 384 00:19:44.920 --> 00:19:48.200 This chaining clearly expresses a step by step daty transformation. 385 00:19:48.480 --> 00:19:52.000 It dramatically improves readability and maintainability. People love it. 386 00:19:52.200 --> 00:19:55.359 I can see why. Okay. And speaking of processing data efficiently, 387 00:19:55.839 --> 00:19:59.559 you mentioned lazy evaluation. The advice was be lazy. What 388 00:19:59.680 --> 00:20:01.759 is that I actually mean in programming? And how does 389 00:20:01.839 --> 00:20:05.400 being lazy help us work with potentially huge or even 390 00:20:05.559 --> 00:20:08.559 endless streams of data without blowing up our memory? 391 00:20:08.680 --> 00:20:08.759 Right? 392 00:20:08.880 --> 00:20:12.160 Lazy evaluation basically means a series of instructions won't be 393 00:20:12.200 --> 00:20:15.160 executed immediately. They'll just sit there waiting for a trigger. 394 00:20:15.680 --> 00:20:18.680 They only do the work when it's absolutely necessary, usually 395 00:20:18.720 --> 00:20:22.319 when you ask for the final result. In Elixir, streams 396 00:20:22.400 --> 00:20:25.920 are the primary mechanism for lazy collections. For instance, creating 397 00:20:25.920 --> 00:20:28.400 a range like one point one zero zero zero zero 398 00:20:28.440 --> 00:20:30.759 zero zero zero zero zero thinks roughly the same tiny 399 00:20:30.759 --> 00:20:33.000 amount of memory is creating one point ten because the 400 00:20:33.079 --> 00:20:36.319 numbers aren't generated up front, they're only generated one by 401 00:20:36.359 --> 00:20:39.039