add peg

peg/Cargo.lock

@@ -0,0 +1,59 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "peg"
+version = "0.1.0"
+dependencies = [
+ "peg 0.6.2",
+]
+
+[[package]]
+name = "peg"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9075875c14bb21f25f11cad4b6ad2e4dd443b8fb83900b2fbdd6ebd744b82e97"
+dependencies = [
+ "peg-macros",
+ "peg-runtime",
+]
+
+[[package]]
+name = "peg-macros"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c24c165fd39e995246140cc78df55c56c6733ba87e6658cb3e197b8856c62852"
+dependencies = [
+ "peg-runtime",
+ "proc-macro2",
+ "quote",
+]
+
+[[package]]
+name = "peg-runtime"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0c1a2897e69d986c7986747ebad425cf03746ec5e3e09bb3b2600f91301ba864"
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "beae6331a816b1f65d04c45b078fd8e6c93e8071771f41b8163255bbd8d7c8fa"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aa563d17ecb180e500da1cfd2b028310ac758de548efdd203e18f283af693f37"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "unicode-xid"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"

peg/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "peg"
+version = "0.1.0"
+authors = ["Hatter Jiang <jht5945@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+peg = "0.6.2"
+

peg/src/main.rs

@@ -0,0 +1,52 @@
+peg::parser!{
+    grammar list_parser() for str {
+      rule number() -> u32
+        = n:$(['0'..='9']+) { n.parse().unwrap() }
+      
+      pub rule list() -> Vec<u32>
+        = "[" l:number() ** "," "]" { l }
+    }
+}
+
+pub trait Node : std::fmt::Debug { fn eval(&self) -> i64; }
+
+#[derive(Debug)]
+struct NumberNode { val: i64, }
+impl Node for NumberNode {
+    fn eval(&self) -> i64 { self.val }
+}
+
+#[derive(Debug)]
+struct AddNode { left: Box<dyn Node>, right: Box<dyn Node>, }
+impl Node for AddNode {
+    fn eval(&self) -> i64 { self.left.eval() + self.right.eval() }
+}
+
+#[derive(Debug)]
+struct SubNode { left: Box<dyn Node>, right: Box<dyn Node>, }
+impl Node for SubNode {
+    fn eval(&self) -> i64 { self.left.eval() - self.right.eval() }
+}
+
+peg::parser!{
+    grammar expression() for str {
+        rule number() -> Box<dyn Node>
+            = n:$(['0'..='9']+) { Box::new(NumberNode{ val: n.parse().unwrap() }) }
+
+        pub rule calculate() -> Box<dyn Node> = precedence!{
+            x:(@) "+" y:@ { Box::new(AddNode{ left: x, right: y, }) }
+            x:(@) "-" y:@ { Box::new(SubNode{ left: x, right: y, }) }
+            --
+            "(" v:calculate() ")" { v }
+            n:number() {n}
+        }
+    }
+}
+
+fn main() {
+    println!("{:?}", list_parser::list("[1,1,2,3,5,8]"));
+
+    let a = expression::calculate("111+444-333");
+    println!("{:?}", a);
+    println!("{}", a.unwrap().eval());
+}