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214 lines
18 KiB
HTML
214 lines
18 KiB
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<title>Tutorial: calc language - Salsa</title>
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<ol class="chapter"><li class="chapter-item expanded "><a href="about_salsa.html"><strong aria-hidden="true">1.</strong> About salsa</a></li><li class="chapter-item expanded affix "><li class="part-title">How to use Salsa</li><li class="chapter-item expanded "><a href="overview.html"><strong aria-hidden="true">2.</strong> Overview</a></li><li class="chapter-item expanded "><a href="tutorial.html" class="active"><strong aria-hidden="true">3.</strong> Tutorial: calc language</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="tutorial/structure.html"><strong aria-hidden="true">3.1.</strong> Basic structure</a></li><li class="chapter-item expanded "><a href="tutorial/jar.html"><strong aria-hidden="true">3.2.</strong> Jars and databases</a></li><li class="chapter-item expanded "><a href="tutorial/db.html"><strong aria-hidden="true">3.3.</strong> Defining the database struct</a></li><li class="chapter-item expanded "><a href="tutorial/ir.html"><strong aria-hidden="true">3.4.</strong> Defining the IR: the various "salsa structs"</a></li><li class="chapter-item expanded "><a href="tutorial/parser.html"><strong aria-hidden="true">3.5.</strong> Defining the parser: memoized functions and inputs</a></li><li class="chapter-item expanded "><a href="tutorial/accumulators.html"><strong aria-hidden="true">3.6.</strong> Defining the parser: reporting errors</a></li><li class="chapter-item expanded "><a href="tutorial/debug.html"><strong aria-hidden="true">3.7.</strong> Defining the parser: debug impls and testing</a></li><li class="chapter-item expanded "><a href="tutorial/checker.html"><strong aria-hidden="true">3.8.</strong> Defining the checker</a></li><li class="chapter-item expanded "><a href="tutorial/interpreter.html"><strong aria-hidden="true">3.9.</strong> Defining the interpreter</a></li></ol></li><li class="chapter-item expanded "><a href="reference.html"><strong aria-hidden="true">4.</strong> Reference</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="reference/durability.html"><strong aria-hidden="true">4.1.</strong> Durability</a></li><li class="chapter-item expanded "><a href="reference/algorithm.html"><strong aria-hidden="true">4.2.</strong> Algorithm</a></li></ol></li><li class="chapter-item expanded "><a href="common_patterns.html"><strong aria-hidden="true">5.</strong> Common patterns</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="common_patterns/on_demand_inputs.html"><strong aria-hidden="true">5.1.</strong> On-demand (Lazy) inputs</a></li></ol></li><li class="chapter-item expanded "><a href="tuning.html"><strong aria-hidden="true">6.</strong> Tuning</a></li><li class="chapter-item expanded "><a href="cycles.html"><strong aria-hidden="true">7.</strong> Cycle handling</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="cycles/fallback.html"><strong aria-hidden="true">7.1.</strong> Recovering via fallback</a></li></ol></li><li class="chapter-item expanded "><li class="part-title">How Salsa works internally</li><li class="chapter-item expanded "><a href="how_salsa_works.html"><strong aria-hidden="true">8.</strong> How Salsa works</a></li><li class="chapter-item expanded "><a href="videos.html"><strong aria-hidden="true">9.</strong> Videos</a></li><li class="chapter-item expanded "><a href="plumbing.html"><strong aria-hidden="true">10.</strong> Plumbing</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="plumbing/jars_and_ingredients.html"><strong aria-hidden="true">10.1.</strong> Jars and ingredients</a></li><li class="chapter-item expanded "><a href="plumbing/database_and_runtime.html"><strong aria-hidden="true">10.2.</strong> Databases and runtime</a></li><li class="chapter-item expanded "><a href="plumbing/db_lifetime.html"><strong aria-hidden="true">10.3.</strong> The db lifetime on tracked/interned structs</a></li><li class="chapter-item expanded "><a href="plumbing/tracked_structs.html"><strong aria-hidden="true">10.4.</strong> Tracked structures</a></li><li class="chapter-item expanded "><a href="plumbing/query_ops.html"><strong aria-hidden="true">10.5.</strong> Query operations</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="plumbing/maybe_changed_after.html"><strong aria-hidden="true">10.5.1.</strong> maybe changed after</a></li><li class="chapter-item expanded "><a href="plumbing/fetch.html"><strong aria-hidden="true">10.5.2.</strong> Fetch</a></li><li class="chapter-item expanded "><a href="plumbing/derived_flowchart.html"><strong aria-hidden="true">10.5.3.</strong> Derived queries flowchart</a></li><li class="chapter-item expanded "><a href="plumbing/cycles.html"><strong aria-hidden="true">10.5.4.</strong> Cycle handling</a></li></ol></li><li class="chapter-item expanded "><a href="plumbing/terminology.html"><strong aria-hidden="true">10.6.</strong> Terminology</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="plumbing/terminology/backdate.html"><strong aria-hidden="true">10.6.1.</strong> Backdate</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/changed_at.html"><strong aria-hidden="true">10.6.2.</strong> Changed at</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/dependency.html"><strong aria-hidden="true">10.6.3.</strong> Dependency</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/derived_query.html"><strong aria-hidden="true">10.6.4.</strong> Derived query</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/durability.html"><strong aria-hidden="true">10.6.5.</strong> Durability</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/input_query.html"><strong aria-hidden="true">10.6.6.</strong> Input query</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/ingredient.html"><strong aria-hidden="true">10.6.7.</strong> Ingredient</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/LRU.html"><strong aria-hidden="true">10.6.8.</strong> LRU</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/memo.html"><strong aria-hidden="true">10.6.9.</strong> Memo</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/query.html"><strong aria-hidden="true">10.6.10.</strong> Query</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/query_function.html"><strong aria-hidden="true">10.6.11.</strong> Query function</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/revision.html"><strong aria-hidden="true">10.6.12.</strong> Revision</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/salsa_item.html"><strong aria-hidden="true">10.6.13.</strong> Salsa item</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/salsa_struct.html"><strong aria-hidden="true">10.6.14.</strong> Salsa struct</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/untracked.html"><strong aria-hidden="true">10.6.15.</strong> Untracked dependency</a></li><li class="chapter-item expanded "><a href="plumbing/terminology/verified.html"><strong aria-hidden="true">10.6.16.</strong> Verified</a></li></ol></li></ol></li><li class="chapter-item expanded "><li class="part-title">Appendices</li><li class="chapter-item expanded "><a href="meta.html"><strong aria-hidden="true">11.</strong> Meta: about the book itself</a></li></ol> </div>
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<h1 class="menu-title">Salsa</h1>
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<h1 id="tutorial-calc"><a class="header" href="#tutorial-calc">Tutorial: calc</a></h1>
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<p>This tutorial walks through an end-to-end example of using Salsa.
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It does not assume you know anything about salsa,
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but reading the <a href="./overview.html">overview</a> first is probably a good idea to get familiar with the basic concepts.</p>
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<p>Our goal is define a compiler/interpreter for a simple language called <code>calc</code>.
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The <code>calc</code> compiler takes programs like the following and then parses and executes them:</p>
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<pre><code>fn area_rectangle(w, h) = w * h
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fn area_circle(r) = 3.14 * r * r
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print area_rectangle(3, 4)
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print area_circle(1)
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print 11 * 2
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</code></pre>
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<p>When executed, this program prints <code>12</code>, <code>3.14</code>, and <code>22</code>.</p>
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<p>If the program contains errors (e.g., a reference to an undefined function), it prints those out too.
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And, of course, it will be reactive, so small changes to the input don't require recompiling (or rexecuting, necessarily) the entire thing.</p>
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