Add block parsing

Right now evaluating a block reduces it to just the last AST in it, will
fix later with environments
This commit is contained in:
greg 2016-01-01 00:52:48 -08:00
parent dd2b4893a4
commit fc11ee753d
2 changed files with 38 additions and 3 deletions

View File

@ -42,6 +42,12 @@ fn reduce_full(ast: AST) -> EvaluatorResult<AST> {
fn reduce_step(ast: AST) -> EvaluatorResult<AST> { fn reduce_step(ast: AST) -> EvaluatorResult<AST> {
use parser::AST::*; use parser::AST::*;
match ast { match ast {
Block(mut block_nodes) => {
match block_nodes.pop() {
None => Err(EvaluatorError { err: format!("Block with no statements") }),
Some(node) => reduce_full(node),
}
},
BinOp(left, op, right) => { BinOp(left, op, right) => {
let left = try!(reduce_full(*left)); let left = try!(reduce_full(*left));
let op = try!(reduce_full(*op)); let op = try!(reduce_full(*op));

View File

@ -9,6 +9,7 @@ pub enum AST {
BinOp(Box<AST>, Box<AST>, Box<AST>), BinOp(Box<AST>, Box<AST>, Box<AST>),
Number(f64), Number(f64),
Name(String), Name(String),
Block(Vec<AST>),
} }
impl fmt::Display for AST { impl fmt::Display for AST {
@ -30,6 +31,10 @@ pub type ParseResult<T> = Result<T, ParseError>;
/* grammar /* grammar
program : block EOF
block : (statement sep)+
sep : NEWLINE | SEMICOLON
statement: expr
expr : term ((PLUS|MIMUS) term)* expr : term ((PLUS|MIMUS) term)*
term : factor ((MUL | DIV) factor)* term : factor ((MUL | DIV) factor)*
factor : NUM | LPAREN expr RPAREN factor : NUM | LPAREN expr RPAREN
@ -98,12 +103,36 @@ impl Parser {
} }
fn parse(&mut self) -> ParseResult<AST> { fn parse(&mut self) -> ParseResult<AST> {
let r = self.expr(); let r = self.block();
try!(self.expect(Token::Newline));
try!(self.expect(Token::EOF)); try!(self.expect(Token::EOF));
r r
} }
fn block(&mut self) -> ParseResult<AST> {
use tokenizer::Token::*;
let mut block_nodes: Vec<AST> = Vec::new();
loop {
let s: AST = try!(self.statement());
block_nodes.push(s);
match self.lookahead() {
Some(Semicolon) | Some(Newline) => {
self.next();
if let Some(EOF) = self.lookahead() {
break
}
},
_ => break
}
}
Ok(AST::Block(block_nodes))
}
fn statement(&mut self) -> ParseResult<AST> {
let r = try!(self.expr());
Ok(r)
}
fn expr(&mut self) -> ParseResult<AST> { fn expr(&mut self) -> ParseResult<AST> {
use tokenizer::Token::*; use tokenizer::Token::*;
let mut lhs = try!(self.term()); let mut lhs = try!(self.term());
@ -157,7 +186,7 @@ impl Parser {
self.next(); self.next();
Ok(AST::Number(n)) Ok(AST::Number(n))
}, },
_ => parse_error!("Expected LParen or NumLiteral") x => parse_error!("Expected LParen or NumLiteral, got {:?}", x )
} }
} }
} }