1 files changed, 91 insertions, 0 deletions
diff --git a/dhall/src/parser.rs b/dhall/src/parser.rs
new file mode 100644
index 0000000..057fce2
--- /dev/null
+++ b/dhall/src/parser.rs
@@ -0,0 +1,91 @@
+use lalrpop_util;
+
+use crate::grammar;
+use crate::grammar_util::BoxExpr;
+use crate::lexer::{Lexer, LexicalError, Tok};
+use crate::core::{bx, Expr};
+
+pub type ParseError<'i> = lalrpop_util::ParseError<usize, Tok<'i>, LexicalError>;
+
+pub fn parse_expr(s: &str) -> Result<BoxExpr, ParseError>  {
+    grammar::ExprParser::new().parse(Lexer::new(s))
+}
+
+use pest::Parser;
+use pest::error::Error;
+use pest::iterators::Pair;
+use crate::generated_parser::{DhallParser, Rule};
+
+fn debug_pair(pair: Pair<Rule>) {
+    fn aux(indent: usize, pair: Pair<Rule>) {
+        let indent_str = "| ".repeat(indent);
+        println!(r#"{}{:?}: "{}""#, indent_str, pair.as_rule(), pair.as_str());
+        for p in pair.into_inner() {
+            aux(indent+1, p);
+        }
+    }
+    aux(0, pair)
+}
+
+pub fn parse_expr_pest(s: &str) -> Result<BoxExpr, Error<Rule>>  {
+    let parsed_expr = DhallParser::parse(Rule::complete_expression, s)?.next().unwrap();
+    debug_pair(parsed_expr.clone());
+    // println!("{}", parsed_expr.clone());
+
+    fn parse_pair(pair: Pair<Rule>) -> BoxExpr {
+        match pair.as_rule() {
+            Rule::natural_literal => bx(Expr::NaturalLit(str::parse(pair.as_str().trim()).unwrap())),
+            Rule::plus_expression => {
+                let mut inner = pair.into_inner().map(parse_pair);
+                let first_expr = inner.next().unwrap();
+                inner.fold(first_expr, |acc, e| bx(Expr::NaturalPlus(acc, e)))
+            }
+            Rule::times_expression => {
+                let mut inner = pair.into_inner().map(parse_pair);
+                let first_expr = inner.next().unwrap();
+                inner.fold(first_expr, |acc, e| bx(Expr::NaturalTimes(acc, e)))
+            }
+            r => panic!("{:?}", r),
+        }
+    }
+
+    Ok(parse_pair(parsed_expr))
+}
+
+
+#[test]
+fn test_parse() {
+    use crate::core::Expr::*;
+    let expr = "((22 + 3) * 10)";
+    println!("{:?}", parse_expr(expr));
+    match parse_expr_pest(expr) {
+        Err(e) => println!("{}", e),
+        ok => println!("{:?}", ok),
+    }
+    assert_eq!(parse_expr_pest(expr).unwrap(), parse_expr(expr).unwrap());
+    assert!(false);
+
+    println!("test {:?}", parse_expr("3 + 5 * 10"));
+    assert!(parse_expr("22").is_ok());
+    assert!(parse_expr("(22)").is_ok());
+    assert_eq!(parse_expr("3 + 5 * 10").ok(),
+               Some(Box::new(NaturalPlus(Box::new(NaturalLit(3)),
+                                Box::new(NaturalTimes(Box::new(NaturalLit(5)),
+                                                      Box::new(NaturalLit(10))))))));
+    // The original parser is apparently right-associative
+    assert_eq!(parse_expr("2 * 3 * 4").ok(),
+               Some(Box::new(NaturalTimes(Box::new(NaturalLit(2)),
+                                 Box::new(NaturalTimes(Box::new(NaturalLit(3)),
+                                                       Box::new(NaturalLit(4))))))));
+    assert!(parse_expr("((((22))))").is_ok());
+    assert!(parse_expr("((22)").is_err());
+    println!("{:?}", parse_expr("\\(b : Bool) -> b == False"));
+    assert!(parse_expr("\\(b : Bool) -> b == False").is_ok());
+    println!("{:?}", parse_expr("foo.bar"));
+    assert!(parse_expr("foo.bar").is_ok());
+    assert!(parse_expr("[] : List Bool").is_ok());
+
+    // println!("{:?}", parse_expr("< Left = True | Right : Natural >"));
+    // println!("{:?}", parse_expr(r#""bl${42}ah""#));
+    // assert!(parse_expr("< Left = True | Right : Natural >").is_ok());
+}