From b5fc8a4a2aeda36e0f49ee7106051f0beee0d81d Mon Sep 17 00:00:00 2001
From: Per Lindgren <per.lindgren@ltu.se>
Date: Thu, 5 Sep 2019 16:44:27 +0200
Subject: [PATCH] examples/main.rs
---
examples/main.rs | 61 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 61 insertions(+)
create mode 100644 examples/main.rs
diff --git a/examples/main.rs b/examples/main.rs
new file mode 100644
index 0000000..ce47c7d
--- /dev/null
+++ b/examples/main.rs
@@ -0,0 +1,61 @@
+extern crate nom;
+
+use nom::combinator::map_res;
+use nom::{
+ branch::alt,
+ bytes::complete::tag,
+ character::complete::{digit1, multispace0},
+ combinator::map,
+ error::{context, VerboseError, VerboseErrorKind},
+ sequence::{preceded, tuple},
+ IResult,
+};
+
+#[derive(Debug, PartialEq)]
+pub enum Op {
+ Add,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum Expr {
+ Num(i32),
+ BinOp(Box<Expr>, Op, Box<Expr>),
+}
+
+pub fn parse_i32(i: &str) -> IResult<&str, Expr> {
+ map(digit1, |digit_str: &str| {
+ Expr::Num(digit_str.parse::<i32>().unwrap())
+ })(i)
+}
+
+fn parse_expr(input: &str) -> IResult<&str, Expr> {
+ preceded(
+ multispace0,
+ alt((
+ map(
+ tuple((parse_i32, preceded(multispace0, tag("+")), parse_expr)),
+ |(l, _, r)| Expr::BinOp(Box::new(l), Op::Add, Box::new(r)),
+ ),
+ parse_i32,
+ )),
+ )(input)
+}
+
+// cargo test
+#[test]
+fn test_parse_i32_1() {
+ let res = parse_expr("2");
+ assert!(res == Ok(("", Expr::Num(1))))
+}
+
+#[test]
+fn test_parse_i32_2() {
+ let _ = parse_expr("1a").is_ok();
+}
+
+fn main() {
+ println!("{:?}", parse_expr("1"));
+ println!("{:?}", parse_expr("1+2 + 3"));
+ println!("{:?}", parse_expr(" 1+ 1a"));
+ println!("{:?}", parse_expr("11111111111111111111111111"));
+}
--
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