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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> 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 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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>
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<h1 class="menu-title">The Puck Programming Language</h1>
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<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>
<blockquote>
<p>! This section is <strong>incomplete</strong>. Proceed with caution.</p>
</blockquote>
<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>elif</code> <code>else</code></li>
<li>pattern matching: <code>match</code> <code>of</code></li>
<li>loops: <code>loop</code> <code>while</code> <code>for</code> <code>in</code></li>
<li>blocks: <code>block</code> <code>break</code> <code>continue</code> <code>return</code></li>
<li>functions: <code>func</code> <code>mut</code> <code>static</code> <code>varargs</code></li>
<li>modules: <code>pub</code> <code>mod</code> <code>use</code> <code>as</code></li>
<li>error handling: <code>try</code> <code>catch</code> <code>finally</code></li>
<li>metaprogramming: <code>macro</code> <code>quote</code> <code>when</code></li>
<li>types: <code>type</code> <code>distinct</code> <code>ref</code></li>
<li>types: <code>struct</code> <code>tuple</code> <code>union</code> <code>enum</code> <code>interface</code></li>
<li>reserved:
<ul>
<li><code>impl</code> <code>object</code> <code>class</code> <code>concept</code> <code>auto</code> <code>empty</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></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>
</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>
<ul>
<li><code>i8</code> <code>i16</code> <code>i32</code> <code>i64</code> <code>i128</code></li>
<li><code>u8</code> <code>u16</code> <code>u32</code> <code>u64</code> <code>u128</code></li>
<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> (params)</li>
<li><code>;</code> (statements)</li>
<li><code>:</code> (types)</li>
<li><code>#</code> (comment)</li>
<li><code>_</code> (unused bindings)</li>
<li><code>|</code> (generics)</li>
<li><code>\</code> (string/char escaping)</li>
<li><code>()</code> (params, tuples)</li>
<li><code>{}</code> (scope, structs)</li>
<li><code>[]</code> (generics, lists)</li>
<li><code>""</code> (strings)</li>
<li><code>''</code> (chars)</li>
<li><code>``</code> (unquoting)</li>
<li>unused: <code>~</code> <code>@</code> <code>$</code> <code>%</code></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 Annotation? '=' Expr
Var ::= 'var' Pattern Annotation? ('=' Expr)?
Const ::= 'pub'? 'const' Pattern Annotation? '=' Expr
Pattern ::= Char | String | Number | Float | Ident | '(' Pattern (',' Pattern)* ')'
Ident '(' Pattern (',' Pattern)* ')'
</code></pre>
<h3 id="declarations"><a class="header" href="#declarations">Declarations</a></h3>
<pre><code>Func ::= 'pub'? 'func' Ident Generics? Parameters? Annotation? '=' Body
Macro ::= 'pub'? 'macro' Ident Generics? Parameters? Annotation? '=' Body
Generics ::= '[' Ident Annotation? (',' Ident Annotation?)* ']'
Parameters ::= '(' Ident Annotation? (',' Ident Annotation?)* ')'
Annotation ::= ':' Type
</code></pre>
<h3 id="types"><a class="header" href="#types">Types</a></h3>
<pre><code>TypeDecl ::= 'pub'? 'type' Ident Generics? '=' Type
Type ::= StructType | TupleType | EnumType | UnionType | Interface |
(('distinct' | 'ref' | 'ptr' | 'mut' | 'static') (Type | ('[' Type ']'))?)
StructType ::= 'struct' ('[' Ident ':' Type (',' Ident ':' Type)* ']')?
UnionType ::= 'union' ('[' Ident ':' Type (',' Ident ':' Type)* ']')?
TupleType ::= 'tuple' ('[' (Ident ':')? Type (',' (Ident ':')? Type)* ']')?
EnumType ::= 'enum' ('[' Ident ('=' Expr)? (',' Ident ('=' Expr)?)* ']')?
Interface ::= 'interface' ('[' Signature (',' Signature)* ']')?
Signature ::= Ident Generics? ('(' Type (',' Type)* ')')? Annotation?
</code></pre>
<h2 id="control-flow"><a class="header" href="#control-flow">Control Flow</a></h2>
<pre><code>If ::= 'if' Expr ':' Body ('elif' Expr ':' Body)* ('else' ':' Body)?
When ::= 'when' Expr ':' Body ('elif' Expr ':' Body)* ('else' ':' Body)?
Try ::= 'try' ':' Body
('except' Ident ('as' Ident)? (',' Ident ('as' Ident)?)*) ':' Body)*
('finally' ':' Body)?
Match ::= 'match' Expr ('of' Pattern (',' Pattern)* ('where' Expr)? ':' Body)+
Block ::= 'block' Ident? ':' Body
Block ::= 'static' ':' Body
Loop ::= 'loop' ':' Body
While ::= 'while' Expr ':' Body
For ::= 'for' Pattern 'in' Expr Body
</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>
<pre><code>Call ::= Ident ('[' Call (',' Call)* ']')? ('(' (Ident '=')? Call (',' (Ident '=')? Call)* ')')? |
Ident Call (',' Call)* |
Call Operator Call? |
Call ':' Body
Expr ::= Let | Var | Const | Func | Type | Mod | Use | Block | Static |
For | While | Loop | If | When | Try | Match | Call
Body ::= Expr | ('{' Expr (';' 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>
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