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diff --git a/docs/book/METAPROGRAMMING.html b/docs/book/METAPROGRAMMING.html new file mode 100644 index 0000000..92bb4cb --- /dev/null +++ b/docs/book/METAPROGRAMMING.html @@ -0,0 +1,290 @@ +<!DOCTYPE HTML> +<html lang="en" class="light" dir="ltr"> + <head> + <!-- Book generated using mdBook --> + <meta charset="UTF-8"> + <title>Metaprogramming - The Puck Programming Language</title> + + + <!-- Custom HTML head --> + + <meta name="description" content=""> + <meta name="viewport" content="width=device-width, initial-scale=1"> + <meta name="theme-color" content="#ffffff"> + + <link rel="icon" href="favicon.svg"> + <link rel="shortcut icon" href="favicon.png"> + <link rel="stylesheet" href="css/variables.css"> + <link rel="stylesheet" href="css/general.css"> + <link rel="stylesheet" href="css/chrome.css"> + <link rel="stylesheet" href="css/print.css" media="print"> + + <!-- Fonts --> + <link rel="stylesheet" href="FontAwesome/css/font-awesome.css"> + <link rel="stylesheet" href="fonts/fonts.css"> + + <!-- Highlight.js Stylesheets --> + <link rel="stylesheet" href="highlight.css"> + <link rel="stylesheet" href="tomorrow-night.css"> + <link rel="stylesheet" href="ayu-highlight.css"> + + <!-- Custom theme stylesheets --> + + </head> + <body class="sidebar-visible no-js"> + <div id="body-container"> + <!-- Provide site root to javascript --> + <script> + var path_to_root = ""; + var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? 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</script> + + <input type="checkbox" id="sidebar-toggle-anchor" class="hidden"> + + <!-- Hide / unhide sidebar before it is displayed --> + <script> + var body = document.querySelector('body'); + var sidebar = null; + var sidebar_toggle = document.getElementById("sidebar-toggle-anchor"); + if (document.body.clientWidth >= 1080) { + try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { } + sidebar = sidebar || 'visible'; + } else { + sidebar = 'hidden'; + } + sidebar_toggle.checked = sidebar === 'visible'; + body.classList.remove('sidebar-visible'); + body.classList.add("sidebar-" + sidebar); + </script> + + <nav id="sidebar" class="sidebar" aria-label="Table of contents"> + <div class="sidebar-scrollbox"> + <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> Basic Types</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.3.</strong> Functions and Calls</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.4.</strong> Boolean and Integer Operations</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.5.</strong> Conditionals and Control Flow</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> Loops and Iterators</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.8.</strong> Modules</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 and Threading</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">1.11.</strong> Advanced Types</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> Indentation Rules [todo]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">2.2.</strong> Reserved Keywords</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">2.3.</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> Using Modules</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">4.2.</strong> Implicit Modules</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">4.3.</strong> Defining Module Interfaces [todo]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">4.4.</strong> Defining an External API [todo]</div></li></ol></li><li class="chapter-item expanded "><a href="ERRORS.html"><strong aria-hidden="true">5.</strong> Error Handling</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">5.1.</strong> Errors as Monads</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">5.2.</strong> Errors as Catchable Exceptions</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">5.3.</strong> Errors and Void Functions [todo]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">5.4.</strong> Unrecoverable Exceptions</div></li></ol></li><li class="chapter-item expanded "><a href="ASYNC.html"><strong aria-hidden="true">6.</strong> Async System</a></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">6.1.</strong> Threading [todo]</div></li></ol></li><li class="chapter-item expanded "><a href="METAPROGRAMMING.html" class="active"><strong aria-hidden="true">7.</strong> Metaprogramming</a></li><li class="chapter-item expanded "><div><strong aria-hidden="true">8.</strong> Memory Management [todo]</div></li><li><ol class="section"><li class="chapter-item expanded "><div><strong aria-hidden="true">8.1.</strong> Reference Counting Optimizations</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">8.2.</strong> Annotations and Ownership</div></li></ol></li><li class="chapter-item expanded "><a href="INTEROP.html"><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, Swift, Nim</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">9.2.</strong> Java, Kotlin</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">9.3.</strong> Python, Racket, C</div></li></ol></li><li class="chapter-item expanded "><div><strong aria-hidden="true">10.</strong> Refinement Types [draft]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">11.</strong> Dependent Types [draft]</div></li><li class="chapter-item expanded "><div><strong aria-hidden="true">12.</strong> Effects System [draft]</div></li></ol> + </div> + <div id="sidebar-resize-handle" class="sidebar-resize-handle"> + <div class="sidebar-resize-indicator"></div> + </div> + </nav> + + <!-- Track and set sidebar scroll position --> + <script> + var sidebarScrollbox = document.querySelector('#sidebar .sidebar-scrollbox'); + sidebarScrollbox.addEventListener('click', function(e) { + if (e.target.tagName === 'A') { + sessionStorage.setItem('sidebar-scroll', sidebarScrollbox.scrollTop); + } + }, { passive: true }); + var sidebarScrollTop = sessionStorage.getItem('sidebar-scroll'); + sessionStorage.removeItem('sidebar-scroll'); + if (sidebarScrollTop) { + // preserve sidebar scroll position when navigating via links within sidebar + 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(Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar"> + <i class="fa fa-search"></i> + </button> + </div> + + <h1 class="menu-title">The Puck Programming Language</h1> + + <div class="right-buttons"> + <a href="print.html" title="Print this book" aria-label="Print this book"> + <i id="print-button" class="fa fa-print"></i> + </a> + + </div> + </div> + + <div id="search-wrapper" class="hidden"> + <form id="searchbar-outer" class="searchbar-outer"> + <input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header"> + </form> + <div id="searchresults-outer" class="searchresults-outer hidden"> + <div id="searchresults-header" class="searchresults-header"></div> + <ul id="searchresults"> + </ul> + </div> + </div> + + <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM --> + <script> + document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible'); + document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible'); + Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) { + link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1); + }); + </script> + + <div id="content" class="content"> + <main> + <h1 id="metaprogramming"><a class="header" href="#metaprogramming">Metaprogramming</a></h1> +<p>Puck has rich metaprogramming support, heavily inspired by Nim. Many features that would have to be at the compiler level in most languages (error propagation <code>?</code>, <code>std.fmt.print</code>, <code>async</code>/<code>await</code>) are instead implemented as macros within the standard library.</p> +<p>Macros take in fragments of the AST within their scope, transform them with arbitrary compile-time code, and spit back out transformed AST fragments to be injected and checked for validity. This is similar to what Nim and the Lisp family of languages do. +By keeping an intentionally minimal AST, some things not possible to express in literal code may be expressible in the AST: in particular, bindings can be injected in many places they could not be injected in ordinarily. (A minimal AST also has the benefit of being quite predictable.)</p> +<p>Macros may not change Puck's syntax: the syntax is flexible enough. Code is syntactically checked (parsed), but <em>not</em> semantically checked (typechecked) before being passed to macros. This may change in the future<!-- (to require arguments to be semantically correct)-->. Macros have the same scope as other routines, that is:</p> +<p><strong>function scope</strong>: takes the arguments within or following a function call</p> +<pre><code class="language-puck">macro print(params: varargs) = + for param in params: + result.add(quote(stdout.write(`params`.str))) + +print(1, 2, 3, 4) +print "hello", " ", "world", "!" +</code></pre> +<p><strong>block scope</strong>: takes the expression following a colon as a single argument</p> +<pre><code class="language-puck">macro my_macro(body) + +my_macro: + 1 + 2 + 3 + 4 +</code></pre> +<p><strong>operator scope</strong>: takes one or two parameters either as a postfix (one parameter) or an infix (two parameters) operator</p> +<pre><code class="language-puck">macro +=(a, b) = + quote: + `a` = `a` + `b` + +a += b +</code></pre> +<p>Macros typically take a list of parameters <em>without</em> types, but they optionally may be given a type to constrain the usage of a macro. Regardless: as macros operate at compile time, their parameters are not instances of a type, but rather an <code>Expr</code> expression representing a portion of the <em>abstract syntax tree</em>. +Similarly, macros always return an <code>Expr</code> to be injected into the abstract syntax tree despite the usual absence of an explicit return type, but the return type may be specified to additionally typecheck the returned <code>Expr</code>.</p> +<pre><code class="language-puck"></code></pre> +<p>As macros operate at compile time, they may not inspect the <em>values</em> that their parameters evaluate to. However, parameters may be marked with <code>static[T]</code>: in which case they will be treated like parameters in functions: as values. (note static parameters may be written as <code>static[T]</code> or <code>static T</code>.) There are many restrictions on what might be <code>static</code> parameters. Currently, it is constrained to literals i.e. <code>1</code>, <code>"hello"</code>, etc, though this will hopefully be expanded to any function that may be evaluated statically in the future.</p> +<pre><code class="language-puck">macro ?[T, E](self: Result[T, E]) = + quote: + match self + of Okay(x): x + of Error(e): return Error(e) + +func meow: Result[bool, ref Err] = + let a = stdin.get()? +</code></pre> +<p>The <code>quote</code> macro is special. It takes in literal code and returns that code <strong>as the AST</strong>. Within quoted data, backticks may be used to break out in order to evaluate and inject arbitrary code: though the code must evaluate to an expression of type <code>Expr</code>. <!-- Variables (of type `Expr`) may be *injected* into the literal code by wrapping them in backticks. This reuse of backticks does mean that defining new operators is impossible within quoted code. --></p> +<pre><code class="language-puck"></code></pre> +<p>The <code>Expr</code> type is available from <code>std.ast</code>, as are many helpers, and combined they provide the construction of arbitrary syntax trees (indeed, <code>quote</code> relies on and emits types of it). It is a <code>union</code> type with its variants directly corresponding to the variants of the internal AST of Puck.</p> +<pre><code class="language-puck"></code></pre> +<p>Construction of macros can be difficult: and so several helpers are provided to ease debugging. The <code>Debug</code> and <code>Display</code> interfaces are implemented for abstract syntax trees: <code>dbg</code> will print a representation of the passed syntax tree as an object, and <code>print</code> will print a best-effort representation as literal code. Together with <code>quote</code> and optionally with <code>static</code>, these can be used to quickly get the representation of arbitrary code.</p> + + </main> + + <nav class="nav-wrapper" aria-label="Page navigation"> + <!-- Mobile navigation buttons --> + <a rel="prev" href="ASYNC.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> + <i class="fa fa-angle-left"></i> + </a> + + <a rel="next prefetch" href="INTEROP.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> + <i class="fa fa-angle-right"></i> + </a> + + <div style="clear: both"></div> + </nav> + </div> + </div> + + <nav class="nav-wide-wrapper" aria-label="Page navigation"> + <a rel="prev" href="ASYNC.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> + <i class="fa fa-angle-left"></i> + </a> + + <a rel="next prefetch" href="INTEROP.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> + <i class="fa fa-angle-right"></i> + </a> + </nav> + + </div> + + <!-- Livereload script (if served using the cli tool) --> + <script> + const wsProtocol = location.protocol === 'https:' ? 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