add pest

pest/src/main.rs

@@ -0,0 +1,18 @@
+extern crate pest_derive;
+extern crate pest;
+
+use pest::Parser as PestParser;
+use pest_derive::Parser;
+
+#[derive(Parser)]
+#[grammar = "sample.pest"]
+struct SampleParser;
+
+
+fn main() {
+    let mut pairs = SampleParser::parse(Rule::expression, "111+222").unwrap_or_else(|e| panic!("{}", e));
+    println!("{:?}", pairs);
+    let a = pairs.next().unwrap().as_str().parse::<i64>().unwrap();
+    pairs.next();
+    let b = pairs.next().unwrap().as_str().parse::<i64>().unwrap();
+}

pest/src/sample.pest

@@ -0,0 +1,2 @@
+number = { ('0'..'9')+ }
+expression = { number ~ "+" ~ number }