Add import statement parsing

easy.reid

@@ -2,6 +2,7 @@
 
 import std::print;
 
+let test = 5;
 let arithmetic = 3 + 2 * 5 + 1 * 2;
 let multiplier = 5 * 2;
 

src/lexer.rs

@@ -1,10 +1,5 @@
 use std::{fmt::Debug, iter::Peekable, str::Chars};
 
-pub static EASIEST: &str = include_str!("../easiest.reid");
-// pub static EASY: &str = include_str!("../easy.reid");
-// pub static MEDIUM: &str = include_str!("../medium.reid");
-// pub static HARD: &str = include_str!("../hard.reid");
-
 static DECIMAL_NUMERICS: &[char] = &['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'];
 
 pub fn tokenize<T: Into<String>>(to_tokenize: T) -> Result<Vec<FullToken>, String> {
@@ -50,6 +45,7 @@ pub fn tokenize<T: Into<String>>(to_tokenize: T) -> Result<Vec<FullToken>, Strin
                 // Check for keywords
                 let variant = match value.as_str() {
                     "let" => Token::LetKeyword,
+                    "import" => Token::ImportKeyword,
                     _ => Token::Identifier(value),
                 };
                 variant
@@ -69,6 +65,11 @@ pub fn tokenize<T: Into<String>>(to_tokenize: T) -> Result<Vec<FullToken>, Strin
             // Single character tokens
             '=' => Token::Equals,
             ';' => Token::Semicolon,
+            ':' => Token::Colon,
+            '+' => Token::Plus,
+            '*' => Token::Times,
+            '(' => Token::ParenOpen,
+            ')' => Token::ParenClose,
             // Invalid token
             _ => Err(format!(
                 "Unknown token '{}' at {}, {}",
@@ -110,12 +111,24 @@ pub type Position = (u32, u32);
 
 #[derive(Debug, Eq, PartialEq, Clone)]
 pub enum Token {
-    LetKeyword,
-    Semicolon,
-    Equals,
+    // Values
     Identifier(String),
     /// Number with at most one decimal point
     DecimalValue(String),
+
+    // Keywords
+    LetKeyword,
+    ImportKeyword,
+
+    // Symbols
+    Semicolon,
+    Equals,
+    Colon,
+    Plus,
+    Times,
+    ParenOpen,  // (
+    ParenClose, // )
+
     Eof,
 }
 

src/main.rs

@@ -1,13 +1,24 @@
-use crate::{lexer::EASIEST, parser::LetStatement, token_stream::TokenStream};
+use crate::{lexer::Token, parser::TopLevelStatement, token_stream::TokenStream};
+
+pub static EASIEST: &str = include_str!("../easiest.reid");
+pub static EASY: &str = include_str!("../easy.reid");
+pub static MEDIUM: &str = include_str!("../medium.reid");
+pub static HARD: &str = include_str!("../hard.reid");
 
 mod lexer;
 mod parser;
 mod token_stream;
 
 fn main() {
-    let tokens = lexer::tokenize(EASIEST).unwrap();
+    let tokens = lexer::tokenize(EASY).unwrap();
+
+    dbg!(&tokens);
+
     let mut token_stream = TokenStream::from(&tokens);
 
-    dbg!(token_stream.parse::<LetStatement>().ok());
-    dbg!(token_stream.parse::<LetStatement>().ok());
+    while let Ok(statement) = token_stream.parse::<TopLevelStatement>() {
+        dbg!(&statement);
+    }
+
+    dbg!(token_stream.expect(Token::Eof).ok());
 }

src/parser.rs

@@ -27,6 +27,22 @@ impl Parseable for Expression {
     }
 }
 
+#[derive(Debug)]
+pub enum TopLevelStatement {
+    Let(LetStatement),
+    Import(ImportStatement),
+}
+
+impl Parseable for TopLevelStatement {
+    fn parse(mut stream: TokenStream) -> Result<Self, ()> {
+        Ok(match stream.peek() {
+            Some(Token::LetKeyword) => TopLevelStatement::Let(stream.parse()?),
+            Some(Token::ImportKeyword) => TopLevelStatement::Import(stream.parse()?),
+            _ => Err(())?,
+        })
+    }
+}
+
 #[derive(Debug)]
 pub struct LetStatement(String, Expression);
 
@@ -45,3 +61,31 @@ impl Parseable for LetStatement {
         }
     }
 }
+
+#[derive(Debug)]
+pub struct ImportStatement(Vec<String>);
+
+impl Parseable for ImportStatement {
+    fn parse(mut stream: TokenStream) -> Result<Self, ()> {
+        stream.expect(Token::ImportKeyword)?;
+
+        let mut import_list = Vec::new();
+
+        if let Some(Token::Identifier(name)) = stream.next() {
+            import_list.push(name);
+            while stream.expect(Token::Colon).is_ok() && stream.expect(Token::Colon).is_ok() {
+                if let Some(Token::Identifier(name)) = stream.next() {
+                    import_list.push(name);
+                } else {
+                    Err(())?
+                }
+            }
+        } else {
+            Err(())?
+        }
+
+        stream.expect(Token::Semicolon)?;
+
+        Ok(ImportStatement(import_list))
+    }
+}