Edits and generation for type switch update
This commit is contained in:
Mark McGranaghan
parent
bee8f55277
commit
a3b3bff8cb
@ -10,7 +10,7 @@ func main() {
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// Here's a basic `switch`.
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i := 2
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fmt.Print("write ", i, " as ")
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fmt.Print("Write ", i, " as ")
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switch i {
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case 1:
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fmt.Println("one")
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@ -25,9 +25,9 @@ func main() {
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// `default` case in this example as well.
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switch time.Now().Weekday() {
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case time.Saturday, time.Sunday:
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fmt.Println("it's the weekend")
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fmt.Println("It's the weekend")
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default:
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fmt.Println("it's a weekday")
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fmt.Println("It's a weekday")
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}
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// `switch` without an expression is an alternate way
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@ -36,26 +36,26 @@ func main() {
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t := time.Now()
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switch {
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case t.Hour() < 12:
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fmt.Println("it's before noon")
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fmt.Println("It's before noon")
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default:
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fmt.Println("it's after noon")
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fmt.Println("It's after noon")
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}
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// A type `switch` compares types instead of values. You
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// can use this to discover the the type of an interface
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// value. In this example, the variable `t` will have the
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// type corresponding to its clause.
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whatAmI := func(i interface{}) string {
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whatAmI := func(i interface{}) {
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switch t := i.(type) {
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case bool:
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return "I am a bool"
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fmt.Println("I'm a bool")
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case int:
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return "I am an int"
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fmt.Println("I'm an int")
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default:
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return fmt.Sprintf("Can't handle type %T", t)
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fmt.Printf("Don't know type %T\n", t)
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}
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}
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fmt.Println(whatAmI(1))
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fmt.Println(whatAmI(true))
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fmt.Println(whatAmI("hey"))
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whatAmI(true)
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whatAmI(1)
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whatAmI("hey")
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}
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@ -1,2 +1,2 @@
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1040d0721b871f78f221a0e9e4a61ea3b0e6de70
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8b5CajPcHn
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d255a1fe931fe471b745aeb66830b10216617479
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kxkBPpY_ue
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@ -1,7 +1,7 @@
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$ go run switch.go
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write 2 as two
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it's the weekend
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it's before noon
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I am an int
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I am a bool
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Can't handle type string
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Write 2 as two
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It's a weekday
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It's after noon
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I'm a bool
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I'm an int
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Don't know type string
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@ -40,7 +40,7 @@ branches.</p>
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</td>
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<td class="code leading">
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<a href="http://play.golang.org/p/8b5CajPcHn"><img title="Run code" src="play.png" class="run" /></a>
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<a href="http://play.golang.org/p/kxkBPpY_ue"><img title="Run code" src="play.png" class="run" /></a>
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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@ -80,7 +80,7 @@ branches.</p>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">i</span> <span class="o">:=</span> <span class="mi">2</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="s">"write "</span><span class="p">,</span> <span class="nx">i</span><span class="p">,</span> <span class="s">" as "</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="s">"Write "</span><span class="p">,</span> <span class="nx">i</span><span class="p">,</span> <span class="s">" as "</span><span class="p">)</span>
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<span class="k">switch</span> <span class="nx">i</span> <span class="p">{</span>
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<span class="k">case</span> <span class="mi">1</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"one"</span><span class="p">)</span>
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@ -105,9 +105,9 @@ in the same <code>case</code> statement. We use the optional
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<div class="highlight"><pre> <span class="k">switch</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Now</span><span class="p">().</span><span class="nx">Weekday</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">case</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Saturday</span><span class="p">,</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Sunday</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"it's the weekend"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"It's the weekend"</span><span class="p">)</span>
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<span class="k">default</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"it's a weekday"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"It's a weekday"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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@ -121,15 +121,43 @@ to express if/else logic. Here we also show how the
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<code>case</code> expressions can be non-constants.</p>
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</td>
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<td class="code">
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">t</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Now</span><span class="p">()</span>
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<span class="k">switch</span> <span class="p">{</span>
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<span class="k">case</span> <span class="nx">t</span><span class="p">.</span><span class="nx">Hour</span><span class="p">()</span> <span class="p"><</span> <span class="mi">12</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"it's before noon"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"It's before noon"</span><span class="p">)</span>
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<span class="k">default</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"it's after noon"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"It's after noon"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>A type <code>switch</code> compares types instead of values. You
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can use this to discover the the type of an interface
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value. In this example, the variable <code>t</code> will have the
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type corresponding to its clause.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">whatAmI</span> <span class="o">:=</span> <span class="kd">func</span><span class="p">(</span><span class="nx">i</span> <span class="kd">interface</span><span class="p">{})</span> <span class="p">{</span>
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<span class="k">switch</span> <span class="nx">t</span> <span class="o">:=</span> <span class="nx">i</span><span class="p">.(</span><span class="kd">type</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">case</span> <span class="kt">bool</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"I'm a bool"</span><span class="p">)</span>
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<span class="k">case</span> <span class="kt">int</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"I'm an int"</span><span class="p">)</span>
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<span class="k">default</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">"Don't know type %T\n"</span><span class="p">,</span> <span class="nx">t</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="p">}</span>
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<span class="nx">whatAmI</span><span class="p">(</span><span class="kc">true</span><span class="p">)</span>
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<span class="nx">whatAmI</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
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<span class="nx">whatAmI</span><span class="p">(</span><span class="s">"hey"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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@ -147,9 +175,12 @@ to express if/else logic. Here we also show how the
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<td class="code">
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<div class="highlight"><pre><span class="gp">$</span> go run switch.go
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<span class="go">write 2 as two</span>
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<span class="go">it's the weekend</span>
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<span class="go">it's before noon</span>
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<span class="go">Write 2 as two</span>
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<span class="go">It's a weekday</span>
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<span class="go">It's after noon</span>
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<span class="go">I'm a bool</span>
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<span class="go">I'm an int</span>
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<span class="go">Don't know type string</span>
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</pre></div>
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</td>
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