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Explain REPL auto-vars in tutorial

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Richard Feldman 2022-10-31 07:45:43 -04:00
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8
www/public/site.css
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@ -24,13 +24,19 @@ code.snippet, samp {
white-space: pre;
padding: 10px 16px;
background-color: #eee;
margin-bottom: 16px;
}
code .ann, samp .ann {
.ann {
/* type annotation - purple in the repl */
color: rebeccapurple;
}
.autovar {
/* automatic variable names in the repl, e.g. # val1 */
color: green;
}
/* Used on on the different-names page. */
th, td {

30
www/public/tutorial/index.html
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@ -42,16 +42,32 @@ short.</p>
<samp>The rockin’ roc repl</samp>
<p>So far, so good!</p>
<h3 id="hello-world">Hello, World!</h3>
<p>Try typing this at the REPL prompt and pressing enter:</p>
<p>Try typing this at the REPL prompt and pressing Enter:</p>
<code class="snippet">"Hello, World!"</code>
<p>The REPL should cheerfully display the following:</p>
<samp>"Hello, World!" <span class="ann">:</span> Str</span></samp>
<samp>"Hello, World!" <span class="ann">:</span> Str</span> <span class="autovar"># val1</span></samp>
<p>Congratulations! You&#39;ve just written your first Roc code!</p>
<h3 id="arithmetic">Arithmetic</h3>
<p>When you entered the <em>expression</em> <code>&quot;Hello, World!&quot;</code> into the REPL,
<h3 id="arithmetic">String Interpolation</h3>
<p>When you entered the <em>expression</em> <code>&quot;Hello, World!&quot;</code>,
the REPL printed it back out. It also printed <code><span class="ann">:</span> Str</code>, because
<code>Str</code> is the expression's type. We'll talk about types later; for now, let's ignore
the <code><span class="ann">:</span></code> and whatever comes after it whenever the REPL prints them.</p>
<code>Str</code> is that expression's type. We'll talk about types later; for now, let's ignore
the <code><span class="ann">:</span></code> and whatever comes after it whenever we see them.</p>
<p>The REPL also printed <code class="autovar"># val1</code> at the end of the line.
That means from now on you can use the variable name <code>val1</code> to refer
to the <code>"Hello, World!"</code> expression you just entered. This comes in handy
when entering complicated expressions! Future sections of the tutorial will omit these labels, since they're
just there as a convenience.</p>
<p>Still, while we're talking about them, let's try it out. Put this into the repl and press Enter:</p>
<code class="snippet">val1</code>
<p>You should see the same <code>"Hello, World!"</code> line as before.</p>
<p>You can also create your own names for expressions. Try entering these lines:</p>
<code class="snippet">greeting = "Hi"</code>
<code class="snippet">audience = "World"</code>
<code class="snippet">"\(greeting), \(audience)!"</code>
<p>After entering that last one, you should see this output:</p>
<samp>"Hi, World!" <span class="ann">:</span> Str</span> <span class="autovar"># val2</span></samp>
<p>This</p>
<h3 id="arithmetic">Arithmetic</h3>
<p>Next let's try putting in a more complicated expression:</p>
<samp>1 + 1
@ -64,7 +80,7 @@ be grouped.</p>
-1 <span class="ann">:</span> Num *</samp>
<h3 id="functions">Functions</h3>
<p>Let&#39;s try calling a function:</p>
<p>Let's try calling a function:</p>
<pre><code class="lang-coffee"><span class="hljs-meta">&gt;&gt;</span> Str.concat <span class="hljs-string">"Hi "</span> <span class="hljs-string">"there!"</span>
<span class="hljs-string">"Hi there!"</span> : Str
</code></pre>