fix a bug in deleting sublsice example

UPDATES.md

@@ -1,3 +1,8 @@
+### 1.13.g (2019/Oct/30)
+
+* fix a bug in the example code in the [Delete a segment of slice elements](https://gfw.go101.org/article/container.html#delete-slice-elements) section
+  of the "Arrays, Slices and Maps in Go" article.
+
 ### 1.13.f (2019/Oct/18)
 
 * correct the explanations for the [Evaluation and Assignment Orders in Assignment Statements](https://go101.org/article/evaluation-orders.html#value-assignment) section

articles/acknowledgements.html

@@ -137,6 +137,7 @@ <h1>Acknowledgements</h1>
 Amargin,
 Tony Bai,
 lanastasov,
+liukaifei,
 etc.
 </p>
 

articles/blocks-and-scopes.html

@@ -87,7 +87,7 @@ <h3>Code Blocks</h3>
 </ul>
 
 <p><i>
-(The differences to Go specification are to make the explanation of identifier shadowing simpler below.)
+(The differences to Go specification are to make the below explanations for identifier shadowing simpler.)
 </i></p>
 
 Here is a picture shows the block hierarchies in a program:
@@ -217,25 +217,29 @@ <h3>Source Code Element Declaration Places</h3>
 Please note,
 <ul>
 <li>
-ignore labels, two code elements can be declared with the same identifier as long as
-the respective innermost containing code blocks of the two declarations are different.
+	if the innermost containing blocks of two code element declarations are the same one,
+	then the names (identifiers) of the two code elements can't be identical.
 </li>
 <li>
-if the innermost containing function body blocks of the two label declarations are the same one,
-then the names (identifiers) of two labels can't be identical.
+	the name (identifier) of a package-level code element declared in a package must not
+	be identical to any package import name declared in any source file in the package.
 </li>
 <li>
-the references of a label must be within the innermost function body block containing the declaration of the label.
+	if the innermost containing function body blocks of two label declarations are the same one,
+	then the names (identifiers) of the two labels can't be identical.
 </li>
 <li>
-some special portions in the implicit local blocks in all kinds of control flows have special requirements.
-Generally, no code elements are allowed to be directly declared in such implicit local blocks, except some short variable declarations.
+	the references of a label must be within the innermost function body block containing the declaration of the label.
+</li>
+<li>
+	some special portions in the implicit local blocks in all kinds of control flows have special requirements.
+	Generally, no code elements are allowed to be directly declared in such implicit local blocks, except some short variable declarations.
 	<ul>
 	<li>
-	Each <code>if</code>, <code>switch</code> or <code>for</code> keyword can be closely followed by a short variable declaration.
+		Each <code>if</code>, <code>switch</code> or <code>for</code> keyword can be closely followed by a short variable declaration.
 	</li>
 	<li>
-	Each <code>case</code> keyword in a <code>select</code> control flow can be closely followed by a short variable declaration.
+		Each <code>case</code> keyword in a <code>select</code> control flow can be closely followed by a short variable declaration.
 	</li>
 	</ul>
 </li>

articles/container.html

@@ -2198,8 +2198,12 @@ <h4>Delete a segment of slice elements</h4>
 s = s[:from + copy(s[from:], s[to:])]
 
 // Don't preserve element orders:
-copy(s[from:to], s[len(s)+from-to:])
-s = s[:len(s)+from-to]
+if n := to-from; len(s)-to < n {
+	copy(s[from:to], s[to:])
+} else {
+	copy(s[from:to], s[len(s)-n:])
+}
+s = s[:len(s)-(to-from)]
 </code></pre>
 
 If the slice elements reference other values, we should reset
@@ -2316,6 +2320,14 @@ <h4>Insert all elements of a slice into another slice</h4>
 s = append(elements, s...)
 </code></pre>
 
+<p>
+The <code>make</code> call in the above code snippet clear the memory allocated for for slice <code>x</code>,
+this is actually an unnecessary operation for this specified use case.
+<a href="https://github.com/golang/go/issues/31592">Future compiler optimization</a> might remove the clear operation.
+</p>
+
+</div>
+
 <h4>Insert several individual elements</h4>
 
 <p>
@@ -2356,8 +2368,6 @@ <h4>More slice operations</h4>
 introduced above in the built-in way.
 </p>
 
-</div>
-
 <h3>Use Maps to Simulate Sets</h3>
 
 <p>

articles/defer-more.html

@@ -176,7 +176,7 @@ <h3>Performance Losses Caused by Deferring Function Calls</h3>
 For the official Go compiler, before version 1.13,
 deferred function calls will cause a few performance losses at run time.
 Since Go SDK 1.13, some simple defer use cases have got optimized.
-Go SDK 1.14 will optimize deferfed calls more.
+Go SDK 1.14 will optimize deferred calls more.
 </p>
 
 <!--

articles/details.html

@@ -2186,6 +2186,9 @@ <h3>Since Go 1.6, we can .</h3>
 https://github.com/golang/go/issues/34684
 syscall.Proc.Call and syscall.LazyProc.Call are not implemented in assembly, and, as such, this rule does not apply to them.
 
+The print result of nil and blank slices are the same. (Similar to maps).
+* history reason
+
 -->
 
 

articles/function-declarations-and-calls.html

@@ -244,8 +244,8 @@ <h3>Function Calls</h3>
 </div>
 
 <p>
-Function calls can be deferred and invoked in new goroutines (green threads) in Go.
-Please read the article <a href="control-flows-more.html">deferred function calls and goroutines</a> for details.
+Function calls can be deferred or invoked in new goroutines (green threads) in Go.
+Please read <a href="control-flows-more.html">a later article</a> for details.
 </p>
 
 <a class="anchor" id="existing-phase"></a>

articles/function.html

@@ -425,7 +425,7 @@ <h4>Use function calls as expressions</h4>
 </p>
 
 If the return results of a call to a multi-result function are not discarded,
-then the call only can be used as a multi-value expression in two scenarios.
+then the call can only be used as a multi-value expression in two scenarios.
 <ol>
 <li>
 	The call can be used in an assignment as source values.

articles/quizzes.html

@@ -5,6 +5,12 @@
 Please follow Go 101's <a href="https://twitter.com/go100and1">official twitter account</a> to get the newest quizzes.):
 
 <ul>
+<li>
+	<a href="https://twitter.com/go100and1/status/1189158330930843648" target="_blank">What does the following Go program print? (21)</a>
+</li>
+<li>
+	<a href="https://twitter.com/go100and1/status/1188841103572623360" target="_blank">What does the following Go program print? (20)</a>
+</li>
 <li>
 	<a href="https://twitter.com/go100and1/status/1187055967168450560" target="_blank">What does the following Go program print? (19)</a>
 </li>

articles/struct.html

@@ -163,8 +163,10 @@ <h3>Struct Value Literals and Struct Value Manipulations</h3>
 
 <p>
 For a value <code>v</code> of type <code>S</code>, we can use
-<code>v.x</code> and <code>v.y</code>, which are called selectors,
+<code>v.x</code> and <code>v.y</code>, which are called selectors (or selector expressions),
 to represent the field values of <code>v</code>.
+<code>v</code> is called the receiver of the selectors.
+
 Later, we call the dot <code>.</code> in a selector as the property selection operator.
 </p>
 
@@ -343,6 +345,8 @@ <h3>In Selectors, Struct Pointers Can Be Used as Struct Values</h3>
 	// Use struct pointers as structs.
 	book2.pages = book1.pages
 	// This last line is eqivalent to the next line.
+	// In other words, if the receiver is a pointer,
+	// it will be automatic dereferenced.
 	(*book2).pages = (*book1).pages
 }
 </code></pre>

articles/tips.html

@@ -784,14 +784,6 @@ <h3>Optimize Go code by making use of BCE (bounds check elimination).</h3>
 
 select may slow: https://twitter.com/melvinodsa/status/1031434710184939522
 
-<a class="anchor" id="embed-unexported-alias-of-exported-type"></a>
-<h3>Embedding an unexported alias of an exported type to avoiding the corresponding anonymous field being modified in user packages.</h3>
-
-	type t = T
-	type X struct {
-		t
-	}
-
 
 try to share Transport for http.Client values. (need a go practice article)
 avoid using the http.Get, ..., functions directly.
@@ -812,7 +804,7 @@ <h3>Embedding an unexported alias of an exported type to avoiding the correspond
 +setting GOMAXPROCS with a value larger than NumCPUs is good for the performance of a program sometimes^M
 +https://news.ycombinator.com/item?id=18350362^
 
-simulate subPackages
+simulate subPackages (not work for exported types)
 	package foo / import "a.b/foo"
 	type SubPkg_ struct{}
 	var SubPkg SubPkg_
@@ -828,8 +820,16 @@ <h3>Embedding an unexported alias of an exported type to avoiding the correspond
 req.WithContext(context.WithValue(req.Context(), paramsKeyType{}, Params{path, tokens})) is slow
 https://github.com/golang/go/issues/28737
 
+
+<a class="anchor" id="embed-unexported-alias-of-exported-type"></a>
+<h3>Embedding an unexported alias of an exported type to avoiding the corresponding anonymous field being modified in user packages.</h3>
+
+	type t = T
+	type X struct {
+		t
+	}
 how to embed an exported type as a non-export field?
-so that package users can modify the field.
+so that package users can't modify the field.
 	type embeddedType = ExportedType
 
 use make() instead of composite literals to initilize map and slice

articles/unofficial-faq.html

@@ -1447,6 +1447,10 @@ <h3>
   * wg align
   * atomic order guarantee
 
+What are the differences between type definition declarations and type alias declarations?
+* direct method set not obtained for definition
+* defined pointer type whose base is interface and pointer can't be embedded
+* method receiver with alias will decalre the method on the rrepresented type
 
 -->