first basic parser

src/parser.rs

@@ -2,7 +2,7 @@ use {
     std::iter::Peekable,
     crate::{
         lexer::{LTIRLexer, LTIRToken, LexError},
-        expr::LTExpr
+        expr::{LTExpr, Statement}
     }
 };
 
@@ -14,20 +14,140 @@ pub enum ParseError {
     UnexpectedToken
 }
 
+pub fn parse_expect<It>(
+    tokens: &mut Peekable<LTIRLexer<It>>,
+    expected_token: LTIRToken
+) -> Result< (), ParseError >
+where It: Iterator<Item = char>
+{
+    match tokens.next() {
+        Some(Ok(t)) => {
+            if t == expected_token {
+                Ok(())
+            } else {
+                Err(ParseError::UnexpectedToken)
+            }
+        },
+        Some(Err(err)) => Err(ParseError::LexError(err)),
+        None => Err(ParseError::UnexpectedEnd)
+    }
+}
+
+pub fn parse_symbol<It>(
+    tokens: &mut Peekable<LTIRLexer<It>>
+) -> Result< String, ParseError >
+where It: Iterator<Item = char>
+{
+    match tokens.next() {
+        Some(Ok(LTIRToken::Symbol(name))) => Ok(name),
+        Some(Ok(_)) => Err(ParseError::UnexpectedToken),
+        Some(Err(err)) => Err(ParseError::LexError(err)),
+        None => Err(ParseError::UnexpectedEnd),
+    }
+}
+
 pub fn parse_statement<It>(
     tokens: &mut Peekable<LTIRLexer<It>>
 ) -> Result< crate::expr::Statement, ParseError >
 where It: Iterator<Item = char>
 {
-    Err(ParseError::UnexpectedEnd)
+    if let Some(peektok) = tokens.peek() {
+        match peektok {
+            Ok(LTIRToken::Symbol(sym)) => {
+                match sym.as_str() {
+                    "!" => {
+                        tokens.next();
+                        let name = parse_symbol(tokens)?;
+                        let val_expr = parse_expr(tokens)?;
+                        let _ = parse_expect(tokens, LTIRToken::StatementSep)?;
+
+                        Ok(Statement::Assignment {
+                            var_id: name,
+                            val_expr
+                        })
+                    }
+                    "while" => {
+                        tokens.next();
+                        let _ = parse_expect(tokens, LTIRToken::ExprOpen)?;
+                        let cond = parse_expr(tokens)?;
+                        let _ = parse_expect(tokens, LTIRToken::ExprClose)?;
+                        Ok(Statement::WhileLoop {
+                            condition: cond,
+                            body: parse_block(tokens)?
+                        })
+                    }
+                    "return" => {
+                        tokens.next();
+                        let expr = parse_expr(tokens)?;
+                        let _ = parse_expect(tokens, LTIRToken::StatementSep)?;
+                        Ok(Statement::Return(parse_expr(tokens)?))
+                    }
+                    _ => {
+                        let expr = parse_expr(tokens)?;
+                        let _ = parse_expect(tokens, LTIRToken::StatementSep)?;
+                        Ok(Statement::Expr(expr))
+                    }
+                }
+            }
+            Ok(_) => {
+                let expr = parse_expr(tokens)?;
+                let _ = parse_expect(tokens, LTIRToken::StatementSep)?;
+                Ok(Statement::Expr(expr))
+            },
+            Err(err) => Err(ParseError::LexError(err.clone()))
+        }
+    } else {
+        Err(ParseError::UnexpectedEnd)
+    }
 }
 
 pub fn parse_block<It>(
     tokens: &mut Peekable<LTIRLexer<It>>
+) -> Result< Vec<Statement>, ParseError >
+where It: Iterator<Item = char>
+{
+    let _ = parse_expect(tokens, LTIRToken::BlockOpen)?;
+
+    let mut statements = Vec::new();
+    while let Some(peektok) = tokens.peek() {
+        match peektok {
+            Ok(LTIRToken::BlockClose) => {
+                tokens.next();
+                return Ok(statements)
+            }
+            Ok(_) => { statements.push( parse_statement(tokens)? ); }
+            Err(err) => { return Err(ParseError::LexError(err.clone())); }
+        }
+    }
+
+    Err(ParseError::UnexpectedEnd)
+}
+
+pub fn parse_atom<It>(
+    tokens: &mut Peekable<LTIRLexer<It>>
 ) -> Result< crate::expr::LTExpr, ParseError >
 where It: Iterator<Item = char>
 {
-    Err(ParseError::UnexpectedEnd)
+    match tokens.next() {
+        Some(Ok(LTIRToken::Symbol(sym))) => {
+            Ok(LTExpr::symbol(sym.as_str()))
+        }
+        Some(Ok(LTIRToken::Char(c))) => {
+            Ok(LTExpr::lit_uint(c as u64))
+        }
+        Some(Ok(LTIRToken::Num(n))) => {
+            Ok(LTExpr::lit_uint(n as u64))
+        }
+        Some(Ok(_)) => {
+            Err(ParseError::UnexpectedToken)
+        }
+        Some(Err(err)) => {
+            Err(ParseError::LexError(err))
+        }
+        None => {
+            Err(ParseError::UnexpectedEnd)
+        }
+    }
 }
 
 pub fn parse_expr<It>(
@@ -37,27 +157,73 @@ where It: Iterator<Item = char>
 {
     let mut children = Vec::new();
 
-    match tokens.next() {
-        Some(Ok(LTIRToken::ExprOpen)) => {
-            if let Ok(subexpr) = parse_expr( tokens ) {
-                
-            } else {
-                
+    while let Some(tok) = tokens.peek() {
+        match tok {
+            Ok(LTIRToken::Lambda) => {
+                if children.len() == 0 {
+                    tokens.next();
+                    let name = parse_symbol(tokens)?;
+                    let body = parse_expr(tokens)?;
+
+                    return Ok(LTExpr::Abstraction{
+                        arg_id: name,
+                        arg_type: None,
+                        val_expr: Box::new(body)
+                    });
+                } else {
+                    return Err(ParseError::UnexpectedToken);
+                }
             }
-/*
-            Err(ParseError::UnexpectedEnd)
-        */
-        },
-        Some(Ok(LTIRToken::BlockOpen)) => {
-            /*
-            Err(ParseError::UnexpectedEnd)
-            */
+            Ok(LTIRToken::ExprOpen) => {
+                tokens.next();
+                while let Some(peektok) = tokens.peek() {
+                    match peektok {
+                        Ok(LTIRToken::ExprClose) => {
+                            tokens.next();
+                            break;
+                        }
+                        _ => {}
+                    }
+                    children.push(parse_expr(tokens)?);
+                }
+            },
+            Ok(LTIRToken::ExprClose) => { break; }
+            Ok(LTIRToken::BlockOpen) => { children.push( LTExpr::block(parse_block(tokens)?)); }
+            Ok(LTIRToken::BlockClose) => { break; }
+            Ok(LTIRToken::StatementSep) => { break; }
+            Ok(LTIRToken::Symbol(name)) => {
+                match name.as_str() {
+                    "if" => {
+                        tokens.next();
+                        let _ = parse_expect(tokens, LTIRToken::ExprOpen)?;
+                        let cond = parse_expr(tokens)?;
+                        let _ = parse_expect(tokens, LTIRToken::ExprClose)?;
+                        let if_expr = LTExpr::block(parse_block(tokens)?);
+                        let mut else_expr = LTExpr::block(vec![]);
+
+                        if let Some(peektok) = tokens.peek() {
+                            if let Ok(LTIRToken::Symbol(name)) = peektok {
+                                if name == "else" {
+                                    tokens.next();
+                                    else_expr = parse_expr(tokens)?;
+                                }
+                            }
+                        }
+
+                        children.push(LTExpr::Branch{
+                            condition: Box::new(cond),
+                            if_expr: Box::new(if_expr),
+                            else_expr: Box::new(else_expr)
+                        });
+                    }
+                    name => {
+                        children.push(parse_atom(tokens)?);
+                    }
+                }
+            }
+            Ok(atom) => { children.push(parse_atom(tokens)?); }
+            Err(err) => { return Err(ParseError::LexError(err.clone())); }
         }
-        /*
-        _ => Err(ParseError::UnexpectedToken),
-        None => Err(ParseError::UnexpectedEnd)
-        */
-        _ => {}
     }
 
     if children.len() > 0 {