From 0e3cd664aff7230c8e5ef1f42bde64431a0464d8 Mon Sep 17 00:00:00 2001
From: Natapat Samutpong <natapat.samutpong@gmail.com>
Date: Thu, 24 Feb 2022 19:33:14 +0700
Subject: [PATCH] some c backend

---
 example/ex.hyc     | 19 +++++-------
 src/back/c.rs      | 76 ++++++++++++++++++++++++++++++++++++++++++++++
 src/back/mod.rs    |  2 ++
 src/front/parse.rs |  5 +--
 src/main.rs        |  9 +++++-
 5 files changed, 97 insertions(+), 14 deletions(-)
 create mode 100644 src/back/c.rs
 create mode 100644 src/back/mod.rs

diff --git a/example/ex.hyc b/example/ex.hyc
index 7bf81af..6d64d19 100644
--- a/example/ex.hyc
+++ b/example/ex.hyc
@@ -1,12 +1,9 @@
-let foo = if 1 == 1 then
-        5
-    else
-        10
-    end;
+let foo = 1;
+let bar = true;
+let baz = "qux";
 
-do
-    print(1);
-end;
-
-fun bar a b = a + b;
-let baz = bar(34 35);
\ No newline at end of file
+if (bar == true) then
+    print(baz);
+else
+    print("quux");
+end;
\ No newline at end of file
diff --git a/src/back/c.rs b/src/back/c.rs
new file mode 100644
index 0000000..2c115ad
--- /dev/null
+++ b/src/back/c.rs
@@ -0,0 +1,76 @@
+use crate::front::parse::Expr;
+
+pub struct Codegen {
+    pub emitted: String,
+}
+
+impl Codegen {
+    pub fn new() -> Self {
+        Self {
+            emitted: String::new(),
+        }
+    }
+
+    fn emit(&mut self, s: String) {
+        self.emitted.push_str(s.as_str());
+    }
+
+    pub fn gen(&mut self, exprs: &[Expr]) {
+        self.emit("#include <stdio.h>\n#include <stdbool.h>\nint main() {\n".to_string());
+        for expr in exprs {
+            self.gen_expr(expr);
+        }
+        self.emit("return 0;\n}\n".to_string());
+    }
+    
+    fn gen_expr(&mut self, expr: &Expr) {
+        match expr {
+            Expr::Let { name, value } => {
+                match &**value {
+                    Expr::Int(i)     => self.emit(format!("int {} = {};\n", name, i)),
+                    Expr::Float(f)   => self.emit(format!("double {} = {};\n", name, f)),
+                    Expr::Boolean(b) => self.emit(format!("bool {} = {};\n", name, b)),
+                    Expr::String(s)  => self.emit(format!("char *{} = \"{}\";\n", name, s)),
+                    _ => todo!(),
+                }
+            },
+            Expr::Call { name, args } => {
+                match &**name {
+                    Expr::Ident(func) => {
+                        match func.as_str() {
+                            "print" => {
+                                self.emit(format!("printf({});\n", match &args[0] {
+                                    Expr::String(s) => format!("\"{}\"", s),
+                                    Expr::Ident(s) => s.to_string(),
+                                    _ => todo!(),
+                                }));
+                            },
+                            _ => todo!(),
+                        }
+                    },
+                    _ => todo!(),
+                }
+            },
+            Expr::If { cond, then, else_ } => {
+                self.emit("if ".to_string());
+                self.gen_expr(&cond);
+                self.emit(" {\n".to_string());
+                self.gen_expr(&then);
+                self.emit("} else {\n".to_string());
+                self.gen_expr(&else_);
+                self.emit("}\n".to_string());
+            },
+            Expr::Binary { left, op, right } => {
+                self.emit("(".to_string());
+                self.gen_expr(&left);
+                self.emit(format!(" {} ", op.to_string()));
+                self.gen_expr(&right);
+                self.emit(")".to_string());
+            },
+            Expr::Ident(s) => self.emit(s.to_string()),
+            Expr::Boolean(b) => self.emit(format!("{}", b)),
+            _ => { println!("{:?}", expr); todo!() },
+        }
+    }
+
+}
\ No newline at end of file
diff --git a/src/back/mod.rs b/src/back/mod.rs
new file mode 100644
index 0000000..fe2aa9b
--- /dev/null
+++ b/src/back/mod.rs
@@ -0,0 +1,2 @@
+/// C compiler backend
+pub mod c;
\ No newline at end of file
diff --git a/src/front/parse.rs b/src/front/parse.rs
index 60d2f51..b9ab89b 100644
--- a/src/front/parse.rs
+++ b/src/front/parse.rs
@@ -26,6 +26,7 @@ pub fn lexer() -> impl Parser<char, Vec<(Token, Span)>, Error = Simple<char>> {
     let int = text::int(10)
         .map(|s: String| Token::Int(s.parse().unwrap()));
 
+    // TODO: this is not working somehow
     let float = text::int(10)
         .then_ignore(just('.'))
         .chain::<char, _, _>(text::digits(10))
@@ -315,7 +316,7 @@ impl Expr {
             Self::String(x)  => out.push_str(&format!("\"{}\"", x)),
             Self::Ident(x)   => out.push_str(&x),
 
-            Self::Unary{ op, expr }         => out.push_str(&format!("({} {})", op, expr.to_sexpr())),
+            Self::Unary{ op, expr } => out.push_str(&format!("({} {})", op, expr.to_sexpr())),
             Self::Binary{ op, left, right } => out.push_str(
                 &format!("({} {} {})", op, left.to_sexpr(), right.to_sexpr())
             ),
@@ -328,7 +329,7 @@ impl Expr {
                 &format!("(fun {} ({})\n  {})", name, args.join(" "), body.to_sexpr())),
 
             Self::If { cond, then, else_ } => out.push_str(
-                &format!("(if {}\n  {}\n  {})", cond.to_sexpr(), then.to_sexpr(), else_.to_sexpr())),
+                &format!("(if {} {} {})", cond.to_sexpr(), then.to_sexpr(), else_.to_sexpr())),
             
             Self::Do { body } => out.push_str(
                 &format!("(do {})", body.iter().map(|x| x.to_sexpr()).collect::<Vec<_>>().join(" "))),
diff --git a/src/main.rs b/src/main.rs
index 289cc84..7b65804 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -12,6 +12,10 @@ use args::{Args, Options};
 pub mod front;
 use front::parse::{lexer, parser};
 
+/// Back-end of the language.
+/// Contains code generator.
+pub mod back;
+
 fn main() {
     let args = Args::parse();
     match args.options {
@@ -24,7 +28,10 @@ fn main() {
                 if parse_error.is_empty() {
                     match ast {
                         Some(ast) => {
-                            println!("{}", ast.iter().map(|e| e.to_sexpr()).collect::<Vec<String>>().join("\n\n"));
+                            // println!("{}", ast.iter().map(|e| e.to_sexpr()).collect::<Vec<String>>().join("\n\n"));
+                            let mut codegen = back::c::Codegen::new();
+                            codegen.gen(&ast);
+                            print!("{}", codegen.emitted);
                         },
                         None => println!("no ast :("),
                     };