Assignments, numbers, funcalls

rust/src/main.rs

@@ -0,0 +1,5 @@
+mod parser;
+
+fn main() {
+    println!("Hello, world!");
+}

rust/src/parser.rs

@@ -0,0 +1,95 @@
+#[derive(Debug,PartialEq)]
+pub enum Statement {
+    Assignment(String, Expression),
+    Funcall(Funcall),
+}
+
+#[derive(Debug,PartialEq)]
+pub enum Expression {
+    Id(String),
+    Num(f64),
+    Funcall(Funcall)
+}
+#[derive(Debug,PartialEq)]
+pub struct Funcall {
+    id: String,
+    args: Vec<Expression>,
+}
+
+peg::parser! {
+    grammar deelang_parser() for str {
+	pub rule program() -> Vec<Statement>
+	    = __* s:statement()* eof() { s }
+	pub rule statement() -> Statement
+	    = i:id() "<-" _ e:expr() __* { Statement::Assignment(i, e) } /
+	    f:funcall() __* { Statement::Funcall(f)}
+	rule expr() -> Expression
+	    = f:funcall() _ { Expression::Funcall(f) } /
+	    i:id() _ { Expression::Id(i) } /
+	    n:num() _ { Expression::Num(n) } 
+	rule id() -> String
+	    = i:$(letter() (letter() / digit() / ['?'|'.'|'-'])*) _ { i.to_string() }
+	rule num() -> f64
+	    = n:$(digit()+ "."? digit()* / "." digit()+) _ { n.to_string().parse().unwrap() }
+	rule funcall() -> Funcall
+	    = i:id() "(" _ e:(expr() ** ("," _)) ")" _ { Funcall{id: i, args: e} }
+	rule letter()
+	    = ['A'..='Z'] / ['a'..='z']
+	rule digit()
+	    = ['0'..='9']
+	rule _ // Non-meaningful whitespace
+	    = ['\t'|' ']*
+	rule __ // Blank lines and lines containing only comments
+	    = comment() &eof() / comment() newline() / newline()
+	rule comment()
+	    = "#" (!newline() [_])* &(newline() / eof())
+	rule newline()
+	    = "\r\n" / "\r" / "\n"
+	rule eof()
+	    = ![_]
+    }
+}
+
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    
+    #[test]
+    fn test_comments() {
+	let expected = vec![];
+	let prgm = "## This is a comment";
+	assert_eq!(deelang_parser::program(prgm).unwrap(), expected);
+    }
+
+    #[test]
+    fn test_funcall() {
+	let expected = vec![
+	    Statement::Funcall(Funcall{id: "pear".to_string(), args: vec![]}),
+ 	    Statement::Funcall(Funcall {
+ 		id: "pear".to_string(),
+ 		args: vec![Expression::Id("x".to_string()), Expression::Id("y".to_string())],
+ 	    })
+	];
+	let prgm = r"pear()
+pear(x, y)";
+	assert_eq!(deelang_parser::program(prgm).unwrap(), expected);
+    }
+
+    #[test]
+    fn test_assignment() {
+	let prgm = r"apple <- 1
+apple <- pear(x, y)";
+	let expected = vec![
+	    Statement::Assignment("apple".to_string(),
+				  Expression::Num(1.0)),
+	    Statement::Assignment("apple".to_string(),
+				  Expression::Funcall(Funcall {
+				      id: "pear".to_string(),
+				      args: vec![
+					  Expression::Id("x".to_string()),
+					  Expression::Id("y".to_string())
+				      ]}))];
+	assert_eq!(deelang_parser::program(prgm).unwrap(), expected);
+    }
+}