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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../index.html">The Puck Programming Language</a></li><li class="chapter-item expanded "><a href="OVERVIEW.html"><strong aria-hidden="true">1.</strong> Basic Usage</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">1.1.</strong> Variables and Comments</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.2.</strong> Functions and Indentation</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.3.</strong> Uniform Function Call Syntax</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.4.</strong> Basic Types</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.5.</strong> Conditionals and Pattern Matching</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.6.</strong> Error Handling</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.7.</strong> Blocks and Loops</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.8.</strong> Module System</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.9.</strong> Compile-time Programming</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.10.</strong> Async System and Threading</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.11.</strong> Memory Management</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.12.</strong> Types System</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.13.</strong> Structs and Tuples</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.14.</strong> Unions and Enums</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.15.</strong> Classes</div></li></ol></li><li class="chapter-item expanded "><a href="SYNTAX.html"><strong aria-hidden="true">2.</strong> Syntax</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">2.1.</strong> Call Syntax</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">2.2.</strong> Indentation Rules</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">2.3.</strong> Expression Rules</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">2.4.</strong> Reserved Keywords</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">2.5.</strong> A Formal Grammar</div></li></ol></li><li class="chapter-item expanded "><a href="TYPES.html"><strong aria-hidden="true">3.</strong> Type System</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">3.1.</strong> Basic Types</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">3.2.</strong> Parameter Types</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">3.3.</strong> Reference Types</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">3.4.</strong> Abstract Types</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">3.5.</strong> Advanced Types</div></li></ol></li><li class="chapter-item expanded "><a href="MODULES.html"><strong aria-hidden="true">4.</strong> Module System</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">4.1.</strong> What are modules?</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">4.2.</strong> Using modules</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">4.3.</strong> Implicit modules</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">4.4.</strong> Defining interfaces [todo]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">4.5.</strong> Defining an external API [todo]</div></li></ol></li><li class="chapter-item expanded "><a href="MEMORY_MANAGEMENT.html"><strong aria-hidden="true">5.</strong> Memory Management [todo]</a></li><li class="chapter-item expanded "><a href="METAPROGRAMMING.html"><strong aria-hidden="true">6.</strong> Metaprogramming</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">6.1.</strong> Scope</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">6.2.</strong> Usage</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">6.3.</strong> Quoting [todo]</div></li></ol></li><li class="chapter-item expanded "><a href="ERRORS.html"><strong aria-hidden="true">7.</strong> Error Handling</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">7.1.</strong> Errors as monads</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">7.2.</strong> Errors as checked exceptions</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">7.3.</strong> Errors as effects [todo]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">7.4.</strong> Unrecoverable Exceptions</div></li></ol></li><li class="chapter-item expanded "><a href="ASYNC.html"><strong aria-hidden="true">8.</strong> Async System</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">8.1.</strong> Effects System [todo]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">8.2.</strong> Threading [todo]</div></li></ol></li><li class="chapter-item expanded "><a href="INTEROP.html" class="active"><strong aria-hidden="true">9.</strong> Language Interop [draft]</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">9.1.</strong> Rust</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">9.2.</strong> Swift, Nim</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">9.3.</strong> Java, Kotlin</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">9.4.</strong> Python, Racket, C</div></li></ol></li><li class="chapter-item expanded "><div><strong aria-hidden="true">10.</strong> Effects System [draft]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">11.</strong> Refinement Types [draft]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">12.</strong> Dependent Types [draft]</div></li><li class="chapter-item expanded "><a href="EXAMPLES.html"><strong aria-hidden="true">13.</strong> Examples</a></li></ol>
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<h1 class="menu-title">The Puck Programming Language</h1>
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<h1 id="interop-with-other-languages"><a class="header" href="#interop-with-other-languages">Interop with Other Languages</a></h1>
<blockquote>
<p>! This section is a <strong>draft</strong>. Many important details have yet to be ironed out.</p>
</blockquote>
<p>A major goal of Puck is <em>minimal-overhead language interoperability</em> while maintaining type safety.</p>
<h2 id="the-problems-of-interop"><a class="header" href="#the-problems-of-interop">The problems of interop</a></h2>
<p>There are three issues that complicate language interop:</p>
<ol>
<li>The language of communication, i.e. the C ABI.</li>
<li>Conflicting type systems, i.e. Python vs. Rust</li>
<li>Conflicting memory management systems, i.e. tracing / reference counting vs. ownership</li>
</ol>
<p>For the first, Puck is being written at the same time as the crABI ABI spec is in development. crABI promises a C-ABI-compatible, cross-language ABI spec: which would <em>dramatically</em> simplify the task of linking to object files produced by other languages (so long as languages actually conform to the ABI). It is being led by the Rust language team, and both Nim and Swift developers have expressed interest in it, which bodes quite well for its future.</p>
<p>For the second, Puck has a type system of similar capability to that of Rust, Nim, and Swift: and thus interop with those languages should be a straightforward exchange of types. Its type system is strictly more powerful than that of Python or C, and so interop requires additional help. Its type system is equally as powerful as but somewhat orthogonal to Java's, and so interop will be a little more difficult.</p>
<p>For the third: Puck uses what amounts to a combination of ownership and reference counting: and thus it is exchangeable in this regard with Rust. Nim and Swift, by contrast, use reference counting: which is not directly compatible with ownership, as attempting to use an owned type as a GC'd reference will immediately lead to a use-after-free. Puck may have to explore some form of gradual typing at linking-time to accommodate making its functions available for use. Using functions from GC'd languages, however, is perfectly doable with the <code>refc</code> type: though this may necessitate copying object graphs over the call boundary.</p>
<p>There is additional significant work being put into the use of Wasm as a language runtime. Wasm allows for - among other things - the <em>sharing</em> of garbage collectors, which means that any garbage-collected language compiling to it can simply use the primitive <code>refc</code> type to denote a garbage-collected reference. This does not, however, immediately work off the bat with ownership: as ownership necessitates certain invariants that garbage collection does not preserve. There is active research into fixing this: notably RichWasm, which retrofits a structural type system with ownership atop Wasm. Such extensions necessitate the runtime environment to implement them, however, and so Puck may have to explore some form of gradual typing for the broader Wasm ecosystem.</p>
<h2 id="usability"><a class="header" href="#usability">Usability</a></h2>
<pre><code class="language-puck">use std.io
use rust.os.linux
use nim.os.sleep
...
</code></pre>
<p>Languages often focus on interop from purely technical details. This <em>is</em> very important: but typically little thought is given to usability (and often none can be, for necessity of compiler support), and so using foreign function interfaces very much feel like using <em>foreign</em> function interfaces. Puck attempts to change that.</p>
<pre><code class="language-puck">@[form(this-function)]
pub func this_function() = ...
</code></pre>
<p>A trivial concern is that identifiers are not always the same across languages: for example, in Racket <code>this-function</code> is a valid identifier, while in Puck the <code>-</code> character is disallowed outright. Matters of convention are issues, too: in Puck, <code>snake_case</code> is preferred for functions and <code>PamelCase</code> for types, but this is certainly not always the case. Puck addresses this at an individual level by attributes allowing for rewriting: and at a language level by consistent rewrite rules.</p>
<p>...todo...</p>
<hr />
<p>Existing systems to learn from:</p>
<ul>
<li><a href="https://doc.rust-lang.org/reference/abi.html">The Rust ABI</a></li>
<li><a href="https://www.hobofan.com/rust-interop/">rust-interop</a></li>
<li><a href="https://github.com/eqrion/cbindgen">CBindGen</a></li>
<li><a href="https://github.com/chinedufn/swift-bridge">swift-bridge</a></li>
<li><a href="https://kotlinlang.org/docs/native-c-interop.html">Kotlin C interop</a></li>
<li><a href="https://github.com/crackcomm/rust-lang-interop">rust-lang-interop</a></li>
<li><a href="https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier">extern in Rust</a></li>
<li><a href="https://github.com/yglukhov/nimpy">NimPy</a></li>
<li><a href="https://github.com/yglukhov/jnim">JNim</a></li>
<li><a href="https://github.com/PMunch/futhark">Futhark</a></li>
<li><a href="https://lib.haxe.org/p/callfunc/">Haxe's <code>callfunc</code></a></li>
</ul>
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