1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
|
<!DOCTYPE HTML>
<html lang="en" class="light" dir="ltr">
<head>
<!-- Book generated using mdBook -->
<meta charset="UTF-8">
<title>Syntax - 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 ? "navy" : "light";
</script>
<!-- Work around some values being stored in localStorage wrapped in quotes -->
<script>
try {
var theme = localStorage.getItem('mdbook-theme');
var sidebar = localStorage.getItem('mdbook-sidebar');
if (theme.startsWith('"') && theme.endsWith('"')) {
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
}
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
}
} catch (e) { }
</script>
<!-- Set the theme before any content is loaded, prevents flash -->
<script>
var theme;
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
if (theme === null || theme === undefined) { theme = default_theme; }
var html = document.querySelector('html');
html.classList.remove('light')
html.classList.add(theme);
var body = document.querySelector('body');
body.classList.remove('no-js')
body.classList.add('js');
</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" class="active"><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"><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
sidebarScrollbox.scrollTop = sidebarScrollTop;
} else {
// scroll sidebar to current active section when navigating via "next/previous chapter" buttons
var activeSection = document.querySelector('#sidebar .active');
if (activeSection) {
activeSection.scrollIntoView({ block: 'center' });
}
}
</script>
<div id="page-wrapper" class="page-wrapper">
<div class="page">
<div id="menu-bar-hover-placeholder"></div>
<div id="menu-bar" class="menu-bar sticky">
<div class="left-buttons">
<label id="sidebar-toggle" class="icon-button" for="sidebar-toggle-anchor" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
<i class="fa fa-bars"></i>
</label>
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
<i class="fa fa-paint-brush"></i>
</button>
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
<li role="none"><button role="menuitem" class="theme" id="light">Light</button></li>
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
</ul>
<button id="search-toggle" class="icon-button" type="button" title="Search. (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="syntax-a-casual-and-formal-look"><a class="header" href="#syntax-a-casual-and-formal-look">Syntax: A Casual and Formal Look</a></h1>
<h2 id="call-syntax"><a class="header" href="#call-syntax">Call Syntax</a></h2>
<p>There is little difference between a function, macro, and operator call. There are only a few forms such calls can take, too, though notably more than most other languages (due to, among other things, uniform function call syntax): hence this section.</p>
<pre><code># The standard, unambiguous call.
routine(1, 2, 3, 4)
# The method call syntax equivalent.
1.routine(2, 3, 4)
# A block-based call. This is only really useful for macros taking in a body.
routine
1
2
3
4
# A parentheses-less call. This is only really useful for `print` and `dbg`.
# Only valid at the start of a line.
routine 1, 2, 3, 4
</code></pre>
<p>Binary operators have some special rules.</p>
<pre><code># Valid call syntaxes for binary operators. What can constitute a binary
# operator is constrained for parsing's sake. Whitespace is optional.
1 + 2
1+2
+ 1, 2 # Only valid at the start of a line. Also, don't do this.
+(1, 2)
</code></pre>
<p>As do unary operators.</p>
<pre><code># The standard call for unary operators. Postfix.
1?
?(1)
</code></pre>
<p>Method call syntax has a number of advantages: notably that it can be <em>chained</em>: acting as a natural pipe operator. Redundant parenthesis can also be omitted.</p>
<pre><code># The following statements are equivalent:
foo.bar.baz
foo().bar().baz()
baz(bar(foo))
baz
bar
foo
baz bar(foo)
baz foo.bar
</code></pre>
<h2 id="indentation-rules"><a class="header" href="#indentation-rules">Indentation Rules</a></h2>
<p>The tokens <code>=</code>, <code>then</code>, <code>do</code>, <code>of</code>, <code>else</code>, <code>block</code>, <code>const</code>, <code>block X</code>, and <code>X</code> (where <code>X</code> is an identifier) are <em>scope tokens</em>. They denote a new scope for their associated expressions (functions/macros/declarations, control flow, loops). The tokens <code>,</code>, <code>.</code> (notably not <code>...</code>), and all default binary operators (notably not <code>not</code>) are <em>continuation tokens</em>. An expression beginning or ending in one of them would always be a syntactic error.</p>
<p>Line breaks are treated as the end of a statement, with several exceptions.</p>
<pre><code class="language-puck">pub func foo() =
print "Hello, world!"
print "This is from a function."
pub func inline_decl() = print "Hello, world!"
</code></pre>
<p>Indented lines following a line ending in a <em>scope token</em> are treated as belonging to a new scope. That is, indented lines following a line ending in a scope token form the body of the expression associated with the scope token.</p>
<p>Indentation is not obligatory after a scope token. However, this necessarily constrains the body of the associated expression to one line: no lines following will be treated as an extension of the body, only the expression associated with the original scope token. (This may change in the future.)</p>
<pre><code class="language-puck">pub func foo(really_long_parameter: ReallyLongType,
another_really_long_parameter: AnotherReallyLongType) = # no indentation! this is ok
print really_long_parameter # this line is indented relative to the first line
print really_long_type
</code></pre>
<p>Lines following a line ending in a <em>continuation token</em> (and, additionally <code>not</code> and <code>(</code>) are treated as a continuation of that line and can have any level of indentation (even negative). If they end in a scope token, however, the following lines must be indented relative to the indentation of the previous line.</p>
<pre><code class="language-puck">let really_long_parameter: ReallyLongType = ...
let another_really_long_parameter: AnotherReallyLongType = ...
really_long_parameter
.foo(another_really_long_parameter) # some indentation! this is ok
</code></pre>
<p>Lines <em>beginning</em> in a continuation token (and, additionally <code>)</code>), too, are treated as a continuation of the previous line and can have any level of indentation. If they end in a scope token, the following lines must be indented relative to the indentation of the previous line.</p>
<pre><code class="language-puck">pub func foo() =
print "Hello, world!"
pub func bar() = # this line is no longer in the above scope.
print "Another function declaration."
</code></pre>
<p>Dedented lines <em>not</em> beginning or ending with a continuation token are treated as no longer in the previous scope, returning to the scope of the according indentation level.</p>
<pre><code class="language-puck">if cond then this
else that
match cond
of this then ...
of that then ...
</code></pre>
<p>A line beginning with a scope token is treated as attached to the previous expression.</p>
<pre><code># Technically allowed. Please don't do this.
let foo
= ...
if cond then if cond then this
else that
for i
in iterable
do ...
match foo of this then ...
of that then ...
match foo of this
then ...
of that then ...
</code></pre>
<p>This <em>can</em> lead to some ugly possibilities for formatting that are best avoided.</p>
<pre><code># Much preferred.
let foo =
...
let foo = ...
if cond then
if cond then
this
else that
if cond then
if cond then this
else that
for i in iterable do
...
for i in iterable do ...
match foo
of this then ...
of that then ...
</code></pre>
<p>The indentation rules are complex, but the effect is such that long statements can be broken <em>almost</em> anywhere.</p>
<h2 id="expression-rules"><a class="header" href="#expression-rules">Expression Rules</a></h2>
<p>First, a word on the distinction between <em>expressions</em> and <em>statements</em>. Expressions return a value. Statements do not. That is all.</p>
<p>There are some syntactic constructs unambiguously recognizable as statements: all declarations, modules, and <code>use</code> statements. There are no syntactic constructs unambiguously recognizable as expressions. As calls returning <code>void</code> are treated as statements, and expressions that return a type could possibly return <code>void</code>, there is no explicit distinction between expressions and statements made in the parser: or anywhere before type-checking.</p>
<p>Expressions can go almost anywhere. Our indentation rules above allow for it.</p>
<pre><code># Some different formulations of valid expressions.
if cond then
this
else
that
if cond then this
else that
if cond
then this
else that
if cond then this else that
let foo =
if cond then
this
else
that
</code></pre>
<pre><code># Some different formulations of *invalid* expressions.
# These primarily break the rule that everything following a scope token
# (ex. `=`, `do`, `then`) not at the end of the line must be self-contained.
let foo = if cond then
this
else
that
let foo = if cond then this
else that
let foo = if cond then this
else that
# todo: how to handle this?
if cond then if cond then that
else that
# shrimple
if cond then
if cond then that
else that
# this should be ok
if cond then this
else that
match foo of
this then ...
of that then ...
</code></pre>
<h2 id="reserved-keywords"><a class="header" href="#reserved-keywords">Reserved Keywords</a></h2>
<p>The following keywords are reserved:</p>
<ul>
<li>variables: <code>let</code> <code>var</code> <code>const</code></li>
<li>control flow: <code>if</code> <code>then</code> <code>elif</code> <code>else</code></li>
<li>pattern matching: <code>match</code> <code>of</code></li>
<li>error handling: <code>try</code> <code>with</code> <code>finally</code></li>
<li>loops: <code>while</code> <code>do</code> <code>for</code> <code>in</code></li>
<li>blocks: <code>loop</code> <code>block</code> <code>break</code> <code>continue</code> <code>return</code></li>
<li>modules: <code>pub</code> <code>mod</code> <code>use</code> <code>as</code></li>
<li>functions: <code>func</code> <code>varargs</code></li>
<li>metaprogramming: <code>macro</code> <code>quote</code> <code>when</code></li>
<li>ownership: <code>lent</code> <code>mut</code> <code>ref</code> <code>refc</code></li>
<li>types: <code>type</code> <code>struct</code> <code>tuple</code> <code>union</code> <code>enum</code> <code>class</code></li>
</ul>
<p>The following keywords are not reserved, but liable to become so.</p>
<ul>
<li><code>impl</code> <code>object</code> <code>interface</code> <code>concept</code> <code>auto</code> <code>effect</code> <code>case</code></li>
<li><code>suspend</code> <code>resume</code> <code>spawn</code> <code>pool</code> <code>thread</code> <code>closure</code> <code>static</code></li>
<li><code>cyclic</code> <code>acyclic</code> <code>sink</code> <code>move</code> <code>destroy</code> <code>copy</code> <code>trace</code> <code>deepcopy</code></li>
</ul>
<p>The following identifiers are in use by the standard prelude:</p>
<ul>
<li>logic: <code>not</code> <code>and</code> <code>or</code> <code>xor</code> <code>shl</code> <code>shr</code> <code>div</code> <code>mod</code> <code>rem</code></li>
<li>logic: <code>+</code> <code>-</code> <code>*</code> <code>/</code> <code><</code> <code>></code> <code><=</code> <code>>=</code> <code>==</code> <code>!=</code> <code>is</code></li>
<li>async: <code>async</code> <code>await</code></li>
<li>types: <code>int</code> <code>uint</code> <code>float</code> <code>i[\d]+</code> <code>u[\d]+</code>
<ul>
<li><code>f32</code> <code>f64</code> <code>f128</code></li>
<li><code>dec64</code> <code>dec128</code></li>
</ul>
</li>
<li>types: <code>bool</code> <code>byte</code> <code>char</code> <code>str</code></li>
<li>types: <code>void</code> <code>never</code></li>
<li>strings: <code>&</code> (string append)</li>
</ul>
<p>The following punctuation is taken:</p>
<ul>
<li><code>=</code> (assignment)</li>
<li><code>.</code> (chaining)</li>
<li><code>,</code> (parameters)</li>
<li><code>;</code> (statements)</li>
<li><code>:</code> (types)</li>
<li><code>#</code> (comment)</li>
<li><code>@</code> (attributes)</li>
<li><code>_</code> (unused bindings)</li>
<li><code>|</code> (generics)</li>
<li><code>\</code> (string/char escaping)</li>
<li><code>()</code> (parameters, tuples)</li>
<li><code>[]</code> (generics, lists)</li>
<li><code>{}</code> (scope, structs)</li>
<li><code>""</code> (strings)</li>
<li><code>''</code> (chars)</li>
<li><code>``</code> (unquoting)</li>
<li>unused on qwerty: <code>~</code> <code>%</code> <code>^</code> <code>$</code>
<ul>
<li>perhaps leave <code>$</code> unused. but <code>~</code>, <code>%</code>, and <code>^</code> totally could be...</li>
</ul>
</li>
</ul>
<h2 id="a-formal-grammar"><a class="header" href="#a-formal-grammar">A Formal Grammar</a></h2>
<p>We now shall take a look at a more formal description of Puck's syntax.</p>
<p>Syntax rules are described in <a href="https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_form">extended Backus–Naur form</a> (EBNF): however, most rules surrounding whitespace, and scope, and line breaks, are modified to how they would appear after a lexing step.</p>
<h3 id="identifiers"><a class="header" href="#identifiers">Identifiers</a></h3>
<pre><code>Ident ::= (Letter | '_') (Letter | Digit | '_')*
Letter ::= 'A'..'Z' | 'a'..'z' | '\x80'..'\xff' # todo
Digit ::= '0'..'9'
</code></pre>
<h3 id="literals"><a class="header" href="#literals">Literals</a></h3>
<pre><code>Int ::= '-'? (DecLit | HexLit | OctLit | BinLit)
Float ::= '-'? DecLit '.' DecLit
BinLit ::= '0b' BinDigit ('_'? BinDigit)*
OctLit ::= '0o' OctDigit ('_'? OctDigit)*
HexLit ::= '0x' HexDigit ('_'? HexDigit)*
DecLit ::= Digit ('_'? Digit)*
BinDigit ::= '0'..'1'
OctDigit ::= '0'..'7'
HexDigit ::= Digit | 'A'..'F' | 'a'..'f'
</code></pre>
<h3 id="chars-strings-and-comments"><a class="header" href="#chars-strings-and-comments">Chars, Strings, and Comments</a></h3>
<pre><code>CHAR ::= '\'' (PRINT - '\'' | '\\\'')* '\''
STRING ::= SINGLE_LINE_STRING | MULTI_LINE_STRING
COMMENT ::= SINGLE_LINE_COMMENT | MULTI_LINE_COMMENT | EXPRESSION_COMMENT
SINGLE_LINE_STRING ::= '"' (PRINT - '"' | '\\"')* '"'
MULTI_LINE_STRING ::= '"""' (PRINT | '\n' | '\r')* '"""'
SINGLE_LINE_COMMENT ::= '#' PRINT*
MULTI_LINE_COMMENT ::= '#[' (PRINT | '\n' | '\r' | MULTI_LINE_COMMENT)* ']#'
EXPRESSION_COMMENT ::= '#;' SINGLE_STMT
PRINT ::= LETTER | DIGIT | OPR |
'"' | '#' | "'" | '(' | ')' | # notably the dual of OPR
',' | ';' | '[' | ']' | '_' |
'`' | '{' | '}' | ' ' | '\t'
</code></pre>
<h3 id="values"><a class="header" href="#values">Values</a></h3>
<pre><code>Value ::= Int | Float | String | Char | Array | Tuple | Struct
Array ::= '[' (Expr (',' Expr)*)? ']'
Tuple ::= '(' (Ident '=')? Expr (',' (Ident '=')? Expr)* ')'
Struct ::= '{' Ident '=' Expr (',' Ident '=' Expr)* '}'
</code></pre>
<h3 id="variables"><a class="header" href="#variables">Variables</a></h3>
<pre><code>Decl ::= Let | Var | Const | Func | Type
Let ::= 'let' Pattern (':' Type)? '=' Expr
Var ::= 'var' Pattern (':' Type)? ('=' Expr)?
Const ::= 'pub'? 'const' Pattern (':' Type)? '=' Expr
Pattern ::= (Ident ('as' Ident)?) | Char | String | Number | Float |
Ident? '(' Pattern (',' Pattern)* ')'
</code></pre>
<h3 id="declarations"><a class="header" href="#declarations">Declarations</a></h3>
<pre><code>Func ::= 'pub'? 'func' Ident Generics? Parameters? (':' Type)? '=' Body
Macro ::= 'pub'? 'macro' Ident Generics? Parameters? (':' Type)? '=' Body
Generics ::= '[' Ident (':' Type)? (',' Ident (':' Type)?)* ']'
Parameters ::= '(' Ident (':' Type)? (',' Ident (':' Type)?)* ')'
</code></pre>
<p>All arguments to functions must have a type. This is resolved at the semantic level, however. (Arguments to macros may lack types. This signifies a generic node.)</p>
<h3 id="types"><a class="header" href="#types">Types</a></h3>
<pre><code>TypeDecl ::= 'pub'? 'type' Ident Generics? '=' Type
Type ::= TypeStruct | TypeTuple | TypeEnum | TypeUnion | SugarUnion |
TypeClass | (Modifier* (Type | ('[' Type ']')))
TypeStruct ::= 'struct' ('[' Ident ':' Type (',' Ident ':' Type)* ']')?
TypeUnion ::= 'union' ('[' Ident ':' Type (',' Ident ':' Type)* ']')?
SugarUnion ::= '(' Ident ':' Type (',' Ident ':' Type)* ')'
TypeTuple ::= 'tuple' ('[' (Ident ':')? Type (',' (Ident ':')? Type)* ']')?
TypeEnum ::= 'enum' ('[' Ident ('=' Expr)? (',' Ident ('=' Expr)?)* ']')?
TypeClass ::= 'class' ('[' Signature (',' Signature)* ']')?
Modifier ::= 'ref' | 'refc' | 'ptr' | 'lent' | 'mut' | 'const'
Signature ::= Ident Generics? ('(' Type (',' Type)* ')')? (':' Type)?
</code></pre>
<h2 id="control-flow"><a class="header" href="#control-flow">Control Flow</a></h2>
<pre><code>If ::= 'if' Expr 'then' Body ('elif' Expr 'then' Body)* ('else' Body)?
When ::= 'when' Expr 'then' Body ('elif' Expr 'then' Body)* ('else' Body)?
Try ::= 'try' Body ('with' Pattern (',' Pattern)* 'then' Body)+ ('finally' Body)?
Match ::= 'match' Expr ('of' Pattern (',' Pattern)* ('where' Expr)? 'then' Body)+
While ::= 'while' Expr 'do' Body
For ::= 'for' Pattern 'in' Expr 'do' Body
Loop ::= 'loop' Body
Block ::= 'block' Ident? Body
Const ::= 'const' Body
Quote ::= 'quote' QuoteBody
</code></pre>
<h2 id="modules"><a class="header" href="#modules">Modules</a></h2>
<pre><code>Mod ::= 'pub'? 'mod' Ident '=' Body
Use ::= 'use' Ident ('.' Ident)* ('.' ('[' Ident (',' Ident)* ']'))?
</code></pre>
<h3 id="operators"><a class="header" href="#operators">Operators</a></h3>
<pre><code>Operator ::= 'and' | 'or' | 'not' | 'xor' | 'shl' | 'shr' |
'div' | 'mod' | 'rem' | 'is' | 'in' | Opr+
Opr ::= '=' | '+' | '-' | '*' | '/' | '<' | '>' |
'@' | '$' | '~' | '&' | '%' | '|' |
'!' | '?' | '^' | '.' | ':' | '\\'
</code></pre>
<h2 id="calls-and-expressions"><a class="header" href="#calls-and-expressions">Calls and Expressions</a></h2>
<p>This section is (quite) inaccurate due to complexities with respect to significant indentation. Heed caution.</p>
<pre><code>Call ::= Ident ('[' Call (',' Call)* ']')? ('(' (Ident '=')? Call (',' (Ident '=')? Call)* ')')? |
Ident Call (',' Call)* |
Call Operator Call? |
Call Body
Stmt ::= Let | Var | Const | Func | Type | Mod | Use | Expr
Expr ::= Block | Const | For | While | Loop | If | When | Try | Match | Call
Body ::= (Stmt ';')* Expr
</code></pre>
<hr />
<p>References:</p>
<ul>
<li><a href="https://www.joshwcomeau.com/javascript/statements-vs-expressions/">Statements vs. Expressions</a></li>
<li><a href="https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html">Swift's Lexical Structure</a></li>
<li><a href="https://nim-lang.github.io/Nim/manual.html">The Nim Programming Language</a></li>
<li><a href="https://pgrandinetti.github.io/compilers/">Pietro's Notes on Compilers</a></li>
</ul>
</main>
<nav class="nav-wrapper" aria-label="Page navigation">
<!-- Mobile navigation buttons -->
<a rel="prev" href="OVERVIEW.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="TYPES.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="OVERVIEW.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="TYPES.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>
<script>
window.playground_copyable = true;
</script>
<script src="elasticlunr.min.js"></script>
<script src="mark.min.js"></script>
<script src="searcher.js"></script>
<script src="clipboard.min.js"></script>
<script src="highlight.js"></script>
<script src="book.js"></script>
<!-- Custom JS scripts -->
</div>
</body>
</html>
|
