{"id":2110,"date":"2020-05-07T00:54:28","date_gmt":"2020-05-06T19:24:28","guid":{"rendered":"https:\/\/golangbyexamples.com\/?p=2110"},"modified":"2020-11-25T00:39:57","modified_gmt":"2020-11-24T19:09:57","slug":"for-loop-in-golang","status":"publish","type":"post","link":"https:\/\/golangbyexamples.com\/for-loop-in-golang\/","title":{"rendered":"For Loop in go (golang)"},"content":{"rendered":"\n<p class=\"has-medium-font-size\">This is the\u00a0 chapter 10 of the golang comprehensive tutorial series. Refer to this link for other chapters of the series \u2013\u00a0<a href=\"https:\/\/golangbyexamples.com\/golang-comprehensive-tutorial\/\">Golang Comprehensive Tutorial Series<\/a><\/p>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Next Tutorial<\/strong>\u00a0\u2013\u00a0 <a href=\"https:\/\/golangbyexamples.com\/understand-for-range-loop-golang\/\">For Range loop<\/a><br><strong>Previous Tutorial<\/strong>\u00a0\u2013 <a href=\"https:\/\/golangbyexamples.com\/constant-golang\/\">Constants<\/a><\/p>\n\n\n\n<p class=\"has-medium-font-size\"><br>Now let\u2019s check out the current tutorial. Below is the table of contents for current tutorial.<\/p>\n\n\n\n<h1 class=\"wp-block-heading\"><strong>Overview<\/strong><\/h1>\n\n\n\n<p class=\"has-medium-font-size\">When it comes to loop, golang has:<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>for loop<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>for-range loop<\/li><\/ul>\n\n\n\n<p class=\"has-medium-font-size\">In this tutorial, we will be learning about the for loop only. The while loop is missing from go but a while loop can be implemented using a for loop as we will see later in this tutorial.<\/p>\n\n\n\n<p class=\"has-medium-font-size\"><br><strong>for<\/strong> loop in GO basically has three parts as shown below in the format<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>init part<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>condition part<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>post part<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">for init_part; condition_part; post_part {\n   ...\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\">Here is the sequence of execution of the three parts:<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>The <strong>init part <\/strong>is executed first before the first iteration<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>The <strong>condition part<\/strong> is executed before every iteration. If the condition is false the loop will exit otherwise the loop will continue to iterate.<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>The <strong>post part<\/strong> is executed after every iteration. After this the condition is check, if it is true then the loop is continued otherwise loop exists.<\/li><\/ul>\n\n\n\n<p class=\"has-medium-font-size\">Some points to note about for loop:<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>The parenthesis is not necessary around for loop but the curly braces around the body is necessary.<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>The <strong>init<\/strong> and <strong>post<\/strong> part is optional.<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>The <strong>init<\/strong> part can be any statement with a short declaration, function call or assignment. If the <strong>init<\/strong> part has the variable declaration, then the scope of that variable is limited to within the for loop.<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>The post part can be any statement but generally contains the increment logic. The post part cannot contain initialization. Compiler will raise error in case we add any initialization logic to the post part<\/li><\/ul>\n\n\n\n<h1 class=\"wp-block-heading\"><strong>Examples<\/strong><\/h1>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Simple for loop<\/strong><\/h2>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    for i := 0; i < 5; i++ {\n        fmt.Println(i)\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">0\n1\n2\n3\n4<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>For loop with only condition<\/strong><\/h2>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    i := 0\n    for i < 5 {\n        fmt.Println(i)\n        i++\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">0\n1\n2\n3\n4<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>For Infinite loop<\/strong><\/h2>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport (\n    \"fmt\"\n    \"time\"\n)\n\nfunc main() {\n    i := 0\n    for {\n        fmt.Println(i)\n        i++\n        time.Sleep(time.Second * 1)\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output: <\/strong>Above program prints a infinite loop<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">0\n1\n2\n3\n4\n5\n.\n.<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Break Statement in For loop<\/strong><\/h2>\n\n\n\n<p class=\"has-medium-font-size\"><strong>break<\/strong> statement help exit out of the for loop. None of the statement after break is executed inside the for loop.<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport (\n    \"fmt\"\n)\n\nfunc main() {\n    i := 0\n    for {\n        fmt.Println(i)\n        i++\n        if i >= 5 {\n            break\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">0\n1\n2\n3\n4<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Continue Statement in For loop<\/strong><\/h2>\n\n\n\n<p class=\"has-medium-font-size\"><strong>continue <\/strong>statement help skip the current iteration of the for loop. None of the statement after the continue is executed and the execution reaches the start again with next iteration. The use case is when you want to only operate on certain elements of the for loop. <\/p>\n\n\n\n<p class=\"has-medium-font-size\">Let's see an exampleIn below program we only want to print non-multiples of 3.<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    for i := 1; i < 10; i++ {\n        if i%3 == 0 {\n            continue\n        }\n        fmt.Println(i)\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-\">1\n2\n4\n5\n7\n8\n10<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Nested For Loop<\/strong><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">for loop can also be nested as well. See below example<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    for i := 0; i < 3; i++ {\n        fmt.Printf(\"Outer loop iteration %d\\n\", i)\n        for j := 0; j < 2; j++ {\n            fmt.Printf(\"i= %d j=%d\\n\", i, j)\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-\">Outer loop iteration 0\ni= 0 j=0\ni= 0 j=1\nOuter loop iteration 1\ni= 1 j=0\ni= 1 j=1\nOuter loop iteration 2\ni= 2 j=0\ni= 2 j=1<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Function Call and Assignment in Init part<\/strong><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">The below code is an example that we can also have function call or assignment in init part too.<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    i := 1\n    \/\/Function call in the init part in for loop\n    for test(); i < 3; i++ {\n        fmt.Println(i)\n    }\n\n    \/\/Assignment in the init part in for loop\n    for i = 2; i < 3; i++ {\n        fmt.Println(i)\n    }\n}\nfunc test() {\n    fmt.Println(\"In test function\")\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">In test function\n1\n2\n2<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Implementing while loop using for loop<\/strong><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">Go doesn't have the <strong>while<\/strong> keyword. Instead it has the <strong>for<\/strong> keyword only. However <strong>for<\/strong> keyword can be used to simulate the functionality same as <strong>while<\/strong>.<\/p>\n\n\n\n<p class=\"has-medium-font-size\"><br><strong>for<\/strong> loop can be implemented to behave the same as <strong>while<\/strong> if <strong>initialization_part<\/strong> and <strong>increment_part<\/strong> can be skipped. Here is an example:<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    i := 1\n    for i <= 5 {\n        fmt.Println(i)\n        i++\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">1\n2\n3\n4\n5<\/code><\/pre>\n\n\n\n<h1 class=\"wp-block-heading\"><strong>Conclusion<\/strong><\/h1>\n\n\n\n<p class=\"has-medium-font-size\">This is all about for loop in golang. Please share feedback\/improvements\/mistakes in comments<\/p>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Next Tutorial<\/strong>\u00a0\u2013\u00a0 <a href=\"https:\/\/golangbyexamples.com\/understand-for-range-loop-golang\/\">For Range loop<\/a><br><strong>Previous Tutorial<\/strong>\u00a0\u2013 <a href=\"https:\/\/golangbyexamples.com\/constant-golang\/\">Constants<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>This is the\u00a0 chapter 10 of the golang comprehensive tutorial series. Refer to this link for other chapters of the series \u2013\u00a0Golang Comprehensive Tutorial Series Next Tutorial\u00a0\u2013\u00a0 For Range loopPrevious Tutorial\u00a0\u2013 Constants&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":"","footnotes":"","jetpack_publicize_message":"","jetpack_is_tweetstorm":false},"categories":[1],"tags":[3,4],"class_list":["post-2110","post","type-post","status-publish","format-standard","hentry","category-tech","tag-go","tag-golang"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.7 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>For Loop in go (golang) - Welcome To Golang By Example<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/golangbyexamples.com\/for-loop-in-golang\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"For Loop in go (golang) - Welcome To Golang By Example\" \/>\n<meta property=\"og:description\" content=\"This is the\u00a0 chapter 10 of the golang comprehensive tutorial series. 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