From 007fdc2ed598fdbdc615fd7cd73caeccb0cba2d2 Mon Sep 17 00:00:00 2001
From: linsy king <linsy_king@sjtu.edu.cn>
Date: Thu, 6 Apr 2023 13:50:11 +0800
Subject: [PATCH] feat: - add hd and tl - add if for better efficency

---
 examples/syn.meow | 30 +++++++++++++++++++---
 src/cat.rs        | 63 +++++++++++++++++++++++++++++++++++++++++++----
 src/expr.lalrpop  |  2 +-
 src/parse.lalrpop |  2 +-
 4 files changed, 87 insertions(+), 10 deletions(-)

diff --git a/examples/syn.meow b/examples/syn.meow
index a644e63..392c6a3 100644
--- a/examples/syn.meow
+++ b/examples/syn.meow
@@ -1,6 +1,6 @@
-true() {"T"}
+T() {"T"}
 
-false() {"F"}
+F() {"F"}
 
 0() {"0"}
 
@@ -116,7 +116,15 @@ in(x,y) {
 }
 
 not(x) {
-    if(x, false(), true())
+    if(x, F(), T())
+}
+
+or(x,y) {
+    if(x,T(), y)
+}
+
+and(x,y) {
+    if(x,y,F())
 }
 
 eq0(x) {
@@ -261,3 +269,19 @@ fib(x) {
         )
     )
 }
+
+tl(x) {
+    var en = {
+        "#$" + enraw(hd(x)) = "#$";
+        encode(x)
+    };
+    decode(en)
+}
+
+wd(x) {
+    if(
+        or(eq(x, ""), eq(hd(x)," ")),
+        "",
+        hd(x) + wd(tl(x))
+    )
+}
diff --git a/src/cat.rs b/src/cat.rs
index b2bb271..b5480da 100644
--- a/src/cat.rs
+++ b/src/cat.rs
@@ -42,6 +42,27 @@ impl Context {
                         body: Vec::new(),
                     }),
                 ),
+                (
+                    "hd".to_string(),
+                    Symbol::Macro(Macro {
+                        args: vec!["x".to_string()],
+                        body: Vec::new(),
+                    }),
+                ),
+                (
+                    "tl".to_string(),
+                    Symbol::Macro(Macro {
+                        args: vec!["x".to_string()],
+                        body: Vec::new(),
+                    }),
+                ),
+                (
+                    "if".to_string(),
+                    Symbol::Macro(Macro {
+                        args: vec!["x".to_string(), "x".to_string(), "x".to_string()],
+                        body: Vec::new(),
+                    }),
+                ),
             ]),
             rules: Vec::new(),
         }
@@ -61,8 +82,8 @@ fn eval_macap(mac: &Macro, args: &Vec<Vec<Tok>>, context: &Box<Context>) -> Stri
 
 fn clear_context(context: &Context) -> Context {
     // clear the context
-    let mut newcontext = Context::new();
-    newcontext.symbols = context
+    let mut newcontext = context.clone();
+    newcontext.symbols = newcontext
         .symbols
         .iter()
         .filter(|(_, v)| match v {
@@ -71,13 +92,14 @@ fn clear_context(context: &Context) -> Context {
         })
         .map(|(k, v)| (k.clone(), v.clone()))
         .collect();
+    newcontext.rules.clear();
     newcontext
 }
 
 fn clear_rules(context: &Context) -> Context {
     // clear the context
-    let mut newcontext = Context::new();
-    newcontext.symbols = context.symbols.clone();
+    let mut newcontext = context.clone();
+    newcontext.rules.clear();
     newcontext
 }
 
@@ -98,7 +120,7 @@ fn apply_rule(x: &String, rules: &Vec<Rule>, context: &mut Box<Context>) -> Stri
 
 fn eval_strict(expr: &mut Vec<Tok>, context: &mut Box<Context>) -> String {
     // Take one argument from the expression
-    // println!("eval strict: {:?}", expr);
+    // println!("[strict] {:?}", expr);
     let first = eat_one_para(expr);
     match &first {
         Tok::Literal(lit) => lit.clone(),
@@ -124,6 +146,37 @@ fn eval_strict(expr: &mut Vec<Tok>, context: &mut Box<Context>) -> String {
                     let y = eval_strict(expr, cleancontext);
                     x + y.as_str()
                 }
+                "hd" => {
+                    // Head of a string
+                    let cleancontext = &mut Box::new(clear_rules(context));
+                    let x = eval_strict(expr, cleancontext);
+                    if x.is_empty() {
+                        String::new()
+                    } else {
+                        x.chars().next().unwrap().to_string()
+                    }
+                }
+                "tl" => {
+                    // Tail of a string
+                    let cleancontext = &mut Box::new(clear_rules(context));
+                    let x = eval_strict(expr, cleancontext);
+                    if x.is_empty() {
+                        String::new()
+                    } else {
+                        x.chars().skip(1).collect()
+                    }
+                }
+                "if" => {
+                    let cleancontext = &mut Box::new(clear_rules(context));
+                    let x = eval_strict(expr, cleancontext);
+                    let y = &mut eval_lazy(expr, cleancontext);
+                    let z = &mut eval_lazy(expr, cleancontext);
+                    if &x == "T" {
+                        eval_strict(y, cleancontext)
+                    } else {
+                        eval_strict(z, cleancontext)
+                    }
+                }
                 _ => {
                     let sym = context
                         .symbols
diff --git a/src/expr.lalrpop b/src/expr.lalrpop
index 3e8842a..c94b092 100644
--- a/src/expr.lalrpop
+++ b/src/expr.lalrpop
@@ -12,7 +12,7 @@ Tokz: Tok = {
 }
 
 VarName: String = {
-    r"[a-z0-9_]*" => String::from_str(<>).unwrap(),
+    r"[a-zA-Z0-9_]*" => String::from_str(<>).unwrap(),
 }
 
 Literal: String = {
diff --git a/src/parse.lalrpop b/src/parse.lalrpop
index 124ec72..df6aa98 100644
--- a/src/parse.lalrpop
+++ b/src/parse.lalrpop
@@ -61,7 +61,7 @@ VarDef: (String, String) = {
 }
 
 VarName: String = {
-    r"[a-z0-9_]*" => String::from_str(<>).unwrap()
+    r"[a-zA-Z0-9_]*" => String::from_str(<>).unwrap()
 }
 
 Literal: String = {