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‎misc/content/2022/06/hands-on-array-in-golang/hands-on-array-in-golang.ipynb‎

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@@ -30,9 +30,8 @@
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" in the sense that the length of an array is part of its type\n",
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" and must be determined at compile time.\n",
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" \n",
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"2. Array is a primitive (value) type in Golang.\n",
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" When assigned to another variable \n",
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" or passed as a parameter,\n",
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"2. When an array is assigned to another variable \n",
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" or passed to a function as a parameter,\n",
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" it is copied!\n",
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" For this reason, \n",
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" array is not a good interface to use.\n",
@@ -480,7 +479,39 @@
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"source": [
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"## [Slice](https://go.dev/ref/spec#Slice_types)\n",
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"\n",
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"Slice in Golang is similar to `Vec` in Rust."
482+
"A Slice in Golang is similar to a dynamic array (or vector) in other programming languages.\n",
483+
"However,\n",
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"due to Golang's unique design (lacking of class),\n",
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"a Slice behaves different and sometimes confusing to users coming from other programming languages.\n",
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"A Slice in Golang is implemented as a descriptor (struct) containing a data pointer, a length and a capacity. \n",
487+
"Due to this design,\n",
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"1. When you pass a Slice (value copy) to a function in Golang,\n",
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" the function can update existing values in the Slice\n",
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" (as the copied Slice in the function shares the same underlying data pointer as the original Slice).\n",
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"2. The built-in function `append` can be used to append values into a slice.\n",
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" Since `append` takes a Slice (instead of a pointer to a Slice) by value,\n",
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" it cannot update the original Slice descriptor (struct),\n",
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" so it has to return a new Slice descriptor.\n",
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" This sounds like append isn't appending in place\n",
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" which is a misunderstanding.\n",
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" - When there's no capacity left in the underlying array,\n",
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" append has to allocate a new chunk of memory and copies value over.\n",
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" Appending isn't in place in this case,\n",
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" but it's true in any programming language.\n",
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" - When there's capacity left in the udnerlying array,\n",
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" appending happens in place in the underlying array\n",
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" (as no new memory allocation is required).\n",
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" However,\n",
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" since a new slice descriptor is returned by `append`\n",
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" and the origial slice descriptor stays the same,\n",
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" the original slice descriptor is still a view of the old array window\n",
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" instead of the new updated array window.\n",
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" - Sometimes,\n",
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" you want to pass a slice to another function for appending values\n",
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" and want the change to be reflected outside the function.\n",
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" To achieve this,\n",
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" you can pass a pointor to the Slice descriptor.\n",
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" "
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]
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},
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{
@@ -666,7 +697,9 @@
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"source": [
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"## Appending to a Slice\n",
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"\n",
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"[Appending to a slice](https://go.dev/tour/moretypes/15)"
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"[Appending to a slice](https://go.dev/tour/moretypes/15)\n",
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"\n",
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"1. Appending to "
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]
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},
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{
@@ -815,18 +848,85 @@
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},
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{
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"<span class=\"gonb-err-location\">/tmp/gonb_e532465a/main.go:3:1: </span> expected declaration, found vec\n",
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"<div class=\"gonb-err-context\">\n",
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"package main\n",
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"\n",
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"<div class=\"gonb-err-line\">vec := []int{78, 89, 45, 56, 14}\n",
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"</div>vec\n",
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"parsing go files in TempDir \"/tmp/gonb_e532465a\": /tmp/gonb_e532465a/main.go:3:1: expected declaration, found vec"
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@@ -855,6 +955,71 @@
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"vec"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 9,
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"a len=0 cap=5 []\n",
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"b len=1 cap=5 [1]\n",
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"a len=0 cap=5 []\n",
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"a len=5 cap=5 [1 0 0 0 0]\n"
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]
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}
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],
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"source": [
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"func printSlice(s string, x []int) {\n",
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"\tfmt.Printf(\"%s len=%d cap=%d %v\\n\",\n",
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"\t\ts, len(x), cap(x), x)\n",
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"}\n",
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"\n",
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"%%\n",
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"a := make([]int, 0, 5)\n",
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"printSlice(\"a\", a)\n",
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"b := append(a, 1)\n",
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"printSlice(\"b\", b)\n",
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"printSlice(\"a\", a)\n",
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"\n",
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"hdr := (*reflect.SliceHeader)(unsafe.Pointer(&a))\n",
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"data := *(*[5]int)(unsafe.Pointer(hdr.Data))\n",
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"printSlice(\"a\", data[:])"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 11,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"a len=0 cap=5 []\n",
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"a len=1 cap=5 [1000]\n"
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]
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}
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],
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"source": [
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"func printSlice(s string, x []int) {\n",
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"\tfmt.Printf(\"%s len=%d cap=%d %v\\n\",\n",
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"\t\ts, len(x), cap(x), x)\n",
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"}\n",
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"\n",
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"func myAppend(arr *[]int, val int) {\n",
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" *arr = append(*arr, val)\n",
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"}\n",
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"\n",
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"%%\n",
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"a := make([]int, 0, 5)\n",
1018+
"printSlice(\"a\", a)\n",
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"myAppend(&a, 1000)\n",
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"printSlice(\"a\", a)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
@@ -868,18 +1033,18 @@
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"metadata": {
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"file_extension": ".py",
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"kernelspec": {
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"display_name": "Go",
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"display_name": "Go (gonb)",
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"language": "go",
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"name": "gophernotes"
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"name": "gonb"
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},
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"language_info": {
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"codemirror_mode": "",
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"file_extension": ".go",
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"mimetype": "",
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"mimetype": "text/x-go",
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"name": "go",
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"nbconvert_exporter": "",
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"pygments_lexer": "",
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"version": "go1.18.3"
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"version": "go1.25.4"
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},
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"mimetype": "text/x-python",
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"name": "python",

‎misc/content/2022/06/string-in-golang/string-in-golang.ipynb‎

Lines changed: 7 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -26,21 +26,18 @@
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"source": [
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"## Tips and Traps\n",
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"\n",
29-
"1. `string` is a primitive type in Golang,\n",
30-
" which means a string value has no methods on it\n",
31-
" but instead you have to use built-in functions \n",
32-
" (e.g., `len`)\n",
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" or functions in other modules \n",
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" (e.g., the `strings` module)\n",
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" to manipulate strings.\n",
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"\n",
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"1. Raw string literals, \n",
29+
"1. In Golang,\n",
30+
" a string is implemented as a struct\n",
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" containing a data pointer (pointing to a read-only slice of bytes)\n",
32+
" and a length.\n",
33+
" \n",
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"2. Raw string literals, \n",
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" delimited by backticks (back quotes), \n",
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" are interpreted literally. \n",
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" They can contain line breaks, \n",
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" and backslashes have no special meaning.\n",
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" \n",
43-
"2. The built-in function `len` returns the length of bytes of a string. \n",
40+
"3. The built-in function `len` returns the length of bytes of a string. \n",
4441
" It is not necessary the length of unicode characters.\n",
4542
" For example,\n",
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" calling `len` on a Chinese character returns 3 instead of 1. "

‎misc/content/2022/06/tips-on-golang/tips-on-golang.ipynb‎

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Original file line numberDiff line numberDiff line change
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"source": [
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"- Author: Benjamin Du\n",
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"- Date: 2022-06-04 17:56:46\n",
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"- Modified: 2025-11-21 10:56:22\n",
9+
"- Modified: 2025-11-28 14:15:20\n",
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"- Title: Tips on Golang\n",
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"- Slug: tips-on-golang\n",
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"- Category: Computer Science\n",
@@ -24,13 +24,25 @@
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"The package `main` tells the Go compiler that \n",
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"the package should compile as an executable program instead of a shared library. \n",
29-
"The `main` function in the `main` package is the entry point of the program.\n",
27+
"## Tips and Traps\n",
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"\n",
31-
" mkdir myproj\n",
32-
" cd myproj\n",
33-
" go mod init legendu.net/myproj"
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"\n",
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"1. The package `main` tells the Go compiler that \n",
31+
" the package should compile as an executable program instead of a shared library. \n",
32+
" The `main` function in the `main` package is the entry point of the program.\n",
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" \n",
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" mkdir myproj\n",
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" cd myproj\n",
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" go mod init legendu.net/myproj\n",
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"\n",
38+
"2. You can play with Golang code in Go Playground.\n",
39+
" Even better,\n",
40+
" you can play with Golang code in a JupyterLab notebook using\n",
41+
" [gonb](https://github.com/janpfeifer/gonb)\n",
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" .\n",
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" A pre-compile Docker images is also available at \n",
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" [janpfeifer/gonb_jupyterlab](https://hub.docker.com/r/janpfeifer/gonb_jupyterlab)\n",
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" ."
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]
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},
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{

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