First pass at putting EBNF grammar into rustdoc
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greg
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a8b9f5046e
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@ -47,7 +47,7 @@ mod builtin;
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mod reduced_ast;
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mod eval;
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/// All bits of state necessary to parse and execute a Schala program are stored in this struct.
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/// All the state necessary to parse and execute a Schala program are stored in this struct.
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/// `state` represents the execution state for the AST-walking interpreter, the other fields
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/// should be self-explanatory.
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pub struct Schala {
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@ -1,3 +1,151 @@
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//! # Parsing
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//! This module is where the recursive-descent parsing methods live.
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//!
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//!
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//! # Schala EBNF Grammar
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//! Terminal productions are in 'single quotes' or UPPERCASE if they are a class of tokens,
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//! or otherwise not representable in ASCII.
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//!
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//! ## Top level structure
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//!
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//! ```
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//! program := (statement delimiter)* EOF
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//! delimiter := NEWLINE | ";"
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//! statement := expression | declaration
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//! block := "{" (statement delimiter)* "}"
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//! declaration := type_declaration | func_declaration | binding_declaration | impl_declaration
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//! ```
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//! ## Declarations - Types
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//! ```
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//! type_declaration := "type" type_declaration_body
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//! type_declaration_body := "alias" type_alias | "mut"? type_singleton_name "=" type_body
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//! type_alias := IDENTIFIER "=" type_name
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//! type_body := variant_specifier ("|" variant_specifier)*
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//! variant_specifier := IDENTIFIER | IDENTIFIER "{" typed_identifier_list "}" | IDENTIFIER "(" type_name* ")"
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//! typed_identifier_list := typed_identifier*
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//! typed_identifier := IDENTIFIER type_anno
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//! ```
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//! ## Declaration - Functions
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//!
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//! ```
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//! func_declaration := func_signature func_body
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//! func_body := ε | nonempty_func_body
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//! nonempty_func_body := "{" (statement delimiter)* "}"
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//! func_signature := "fn" func_name formal_param_list type_anno+
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//! func_name := IDENTIFIER | operator
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//! formal_param_list := "(" (formal_param ",")* ")"
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//! formal_param := IDENTIFIER type_anno+
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//! ```
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//!
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//! ## Declaration - Variable bindings
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//! ```binding_declaration := "let" "mut"? IDENTIFIER "=" expresion```
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//!
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//! ## Declaration - Interface
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//!
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//! ```
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//! interface_declaration := "interface" type_singleton_name signature_block
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//! impl_declaration := "impl" type_singleton_name decl_block | "impl" type_singleton_name "for" type_name decl_block
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//! decl_block := "{" (func_declaration)* "}"
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//! signature_block := "{" (func_signature)* "}"
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//! ```
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//!
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//! ## Type Annotations
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//!
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//! ```
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//! type_anno := (":" type_name)+
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//! type_name := type_singleton_name | "(" type_names ")"
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//! type_names := ε | type_name (, type_name)*
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//! type_singleton_name = IDENTIFIER (type_params)*
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//! type_params := "<" type_name (, type_name)* ">"
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//! ```
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//!
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//! ## Expressions
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//! ```
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//! expression := precedence_expr type_anno+
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//! precedence_expr := prefix_expr
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//! prefix_expr := prefix_op call_expr
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//! prefix_op := "+" | "-" | "!" | "~"
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//! call_expr := index_expr ( "(" expr_list ")" )* | ε
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//! ```
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//!
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//! ```
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//! expr_list := expression ("," expression)* | ε
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//! index_expr := primary ( "[" (expression ("," (expression)* | ε) "]" )*
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//! primary := literal | paren_expr | if_expr | for_expr | while_expr | identifier_expr | lambda_expr | anonymous_struct | list_expr
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//! ```
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//!
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//! ## Primary expressions
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//!
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//! ```
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//! list_expr := "[" (expression, ",")* "]"
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//! lambda_expr := "\\" lambda_param_list type_anno+ nonempty_func_body
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//! lambda_param_list := formal_param_list | formal_param
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//! paren_expr := LParen paren_inner RParen
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//! paren_inner := (expression ",")*
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//! identifier_expr := named_struct | IDENTIFIER
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//! ```
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//!
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//! Expression literals
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//! ```
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//! literal := "true" | "false" | number_literal | STR_LITERAL
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//! named_struct := IDENTIFIER record_block
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//! record_block := "{" (record_entry, ",")* | "}" //TODO support anonymus structs, update syntax
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//! record_entry := IDENTIFIER ":" expression
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//! anonymous_struct := TODO
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//! ```
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//!
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//! A `float_literal` can still be assigned to an int in type-checking
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//! ```
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//! number_literal := int_literal | float_literal
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//! int_literal = ("0x" | "0b") digits
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//! float_literal := digits ("." digits)
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//! digits := (DIGIT_GROUP underscore)+
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//! ```
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//!
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//! ## Patterns
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//! ```
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//! pattern := "(" (pattern, ",")* ")" | simple_pattern
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//! simple_pattern := pattern_literal | record_pattern | tuple_struct_pattern
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//! pattern_literal := "true" | "false" | signed_number_literal | STR_LITERAL | IDENTIFIER
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//! signed_number_literal := "-"? number_literal
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//! record_pattern := IDENTIFIER "{" (record_pattern_entry, ",")* "}"
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//! record_pattern_entry := IDENTIFIER | IDENTIFIER ":" Pattern
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//! tuple_struct_pattern := IDENTIFIER "(" (pattern, ",")* ")"
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//! ```
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//!
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//! ```
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//! expr_or_block := "{" (statement delimiter)* "}" | expr
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//! ```
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//!
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//! ## If-expressions
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//! ```
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//! if_expr := "if" discriminator ("then" condititional | "is" simple_pattern_match | guard_block)
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//! discriminator := precedence_expr (operator)+
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//! conditional := expr_or_block else_clause
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//! simple_pattern_match := pattern "then" conditional
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//! else_clause := ε | "else" expr_or_block
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//! guard_block := "{" (guard_arm, ",")* "}"
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//! guard_arm := guard "->" expr_or_block
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//! guard := "is" pattern | (operator)+ precedence_expr
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//! ```
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//!
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//! ## While expressions
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//! ```
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//! while_expr := "while" while_cond "{" (statement delimiter)* "}"
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//! while_cond := ε | expression | expression "is" pattern //TODO maybe is-expresions should be primary
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//! ```
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//!
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//! //TODO this implies there must be at least one enumerator, which the parser doesn"t support right
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//! //this second, and maybe should fail later anyway
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//! ## For-expressions
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//! ```
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//! for_expr := "for" (enumerator | "{" enumerators "}") for_expr_body
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//! for_expr_body := "return" expression | "{" (statement delimiter)* "}"
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//! enumerators := enumerator ("," enumerators)*
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//! enumerator := identifier "<-" expression | identifier "=" expression //TODO add guards, etc.
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//! ```
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//!
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use std::rc::Rc;
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use std::iter::Peekable;
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use std::vec::IntoIter;
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@ -10,6 +158,7 @@ use crate::ast::*;
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use crate::builtin::{BinOp, PrefixOp};
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/// Represents a parsing error
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#[derive(Debug)]
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pub struct ParseError {
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pub msg: String,
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@ -22,6 +171,7 @@ impl ParseError {
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}
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}
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/// Represents either a successful parsing result or a ParseError
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pub type ParseResult<T> = Result<T, ParseError>;
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#[derive(Debug)]
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@ -31,6 +181,7 @@ pub struct ParseRecord {
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level: u32,
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}
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/// Main data structure for doing parsing.
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pub struct Parser {
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token_handler: TokenHandler,
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parse_record: Vec<ParseRecord>,
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@ -69,6 +220,7 @@ impl TokenHandler {
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}
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impl Parser {
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/// Create a new parser initialized with some tokens.
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pub fn new(initial_input: Vec<Token>) -> Parser {
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Parser {
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token_handler: TokenHandler::new(initial_input),
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@ -78,6 +230,7 @@ impl Parser {
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}
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}
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/// Parse all loaded tokens up to this point.
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pub fn parse(&mut self) -> ParseResult<AST> {
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self.program()
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}
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@ -155,128 +308,10 @@ macro_rules! delimited {
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};
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}
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/* Schala EBNF Grammar */
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/* Terminal productions are in 'single quotes' or UPPERCASE if they are a class
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* or not representable in ASCII
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/* Top-level Structure */
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program := (statement delimiter)* EOF
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delimiter := NEWLINE | ';'
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statement := expression | declaration
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block := '{' (statement delimiter)* '}'
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declaration := type_declaration | func_declaration | binding_declaration | impl_declaration
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/* Declarations - Types */
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type_declaration := 'type' type_declaration_body
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type_declaration_body := 'alias' type_alias | 'mut'? type_singleton_name '=' type_body
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type_alias := IDENTIFIER '=' type_name
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type_body := variant_specifier ('|' variant_specifier)*
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variant_specifier := IDENTIFIER | IDENTIFIER '{' typed_identifier_list '}' | IDENTIFIER '(' type_name* ')'
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typed_identifier_list := typed_identifier*
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typed_identifier := IDENTIFIER type_anno
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/* Declaration - Functions */
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func_declaration := func_signature func_body
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func_body := ε | nonempty_func_body
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nonempty_func_body := '{' (statement delimiter)* '}'
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func_signature := 'fn' func_name formal_param_list type_anno+
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func_name := IDENTIFIER | operator
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formal_param_list := '(' (formal_param ',')* ')'
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formal_param := IDENTIFIER type_anno+
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/* Declaration - Variable bindings */
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binding_declaration := 'let' 'mut'? IDENTIFIER '=' expresion
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/* Declaration - Interface */
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interface_declaration := 'interface' type_singleton_name signature_block
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impl_declaration := 'impl' type_singleton_name decl_block | 'impl' type_singleton_name 'for' type_name decl_block
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decl_block := '{' (func_declaration)* '}'
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signature_block := '{' (func_signature)* '}'
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/* Type annotations */
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type_anno := (':' type_name)+
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type_name := type_singleton_name | '(' type_names ')'
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type_names := ε | type_name (, type_name)*
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type_singleton_name = IDENTIFIER (type_params)*
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type_params := '<' type_name (, type_name)* '>'
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/* Expressions */
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expression := precedence_expr type_anno+
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precedence_expr := prefix_expr
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prefix_expr := prefix_op call_expr
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prefix_op := '+' | '-' | '!' | '~'
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call_expr := index_expr ( '(' expr_list ')' )* | ε
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expr_list := expression (',' expression)* | ε
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index_expr := primary ( '[' (expression (',' (expression)* | ε) ']' )*
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primary := literal | paren_expr | if_expr | for_expr | while_expr | identifier_expr | lambda_expr | anonymous_struct | list_expr
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/* Primary Expressions */
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list_expr := '[' (expression, ',')* ']'
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lambda_expr := '\' lambda_param_list type_anno+ nonempty_func_body
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lambda_param_list := formal_param_list | formal_param
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paren_expr := LParen paren_inner RParen
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paren_inner := (expression ',')*
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identifier_expr := named_struct | IDENTIFIER
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/* Expression - Literals */
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literal := 'true' | 'false' | number_literal | STR_LITERAL
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named_struct := IDENTIFIER record_block
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record_block := '{' (record_entry, ',')* | '}' //TODO support anonymus structs, update syntax
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record_entry := IDENTIFIER ':' expression
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anonymous_struct := TODO
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// a float_literal can still be assigned to an int in type-checking
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number_literal := int_literal | float_literal
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int_literal = ('0x' | '0b') digits
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float_literal := digits ('.' digits)
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digits := (DIGIT_GROUP underscore)+
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/* Pattern syntax */
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pattern := '(' (pattern, ',')* ')' | simple_pattern
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simple_pattern := pattern_literal | record_pattern | tuple_struct_pattern
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pattern_literal := 'true' | 'false' | signed_number_literal | STR_LITERAL | IDENTIFIER
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signed_number_literal := '-'? number_literal
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record_pattern := IDENTIFIER '{' (record_pattern_entry, ',')* '}'
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record_pattern_entry := IDENTIFIER | IDENTIFIER ':' Pattern
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tuple_struct_pattern := IDENTIFIER '(' (pattern, ',')* ')'
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expr_or_block := '{' (statement delimiter)* '}' | expr
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/* Expression - If */
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if_expr := 'if' discriminator ('then' condititional | 'is' simple_pattern_match | guard_block)
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discriminator := precedence_expr (operator)+
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conditional := expr_or_block else_clause
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simple_pattern_match := pattern 'then' conditional
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else_clause := ε | 'else' expr_or_block
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guard_block := '{' (guard_arm, ',')* '}'
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guard_arm := guard '->' expr_or_block
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guard := 'is' pattern | (operator)+ precedence_expr
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/* Expression - While */
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while_expr := 'while' while_cond '{' (statement delimiter)* '}'
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while_cond := ε | expression | expression 'is' pattern //TODO maybe is-expresions should be primary
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//TODO this implies there must be at least one enumerator, which the parser doesn't support right
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//this second, and maybe should fail later anyway
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/* Expression - For */
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for_expr := 'for' (enumerator | '{' enumerators '}') for_expr_body
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for_expr_body := 'return' expression | '{' (statement delimiter)* '}
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enumerators := enumerator (',' enumerators)*
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enumerator := identifier '<-' expression | identifier '=' expression //TODO add guards, etc.
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*/
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impl Parser {
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/// `program := (statement delimiter)* EOF`
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/// `delimiter := NEWLINE | ';'`
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#[recursive_descent_method]
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fn program(&mut self) -> ParseResult<AST> {
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let mut statements = Vec::new();
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@ -295,6 +330,7 @@ impl Parser {
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Ok(AST(statements))
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}
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/// `statement := expression | declaration`
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#[recursive_descent_method]
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fn statement(&mut self) -> ParseResult<Statement> {
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//TODO handle error recovery here
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