From db854fb02faed099529ea6f363cf3cb56df5603a Mon Sep 17 00:00:00 2001
From: linsy king <linsy_king@sjtu.edu.cn>
Date: Wed, 5 Apr 2023 22:40:14 +0800
Subject: [PATCH] fix

---
 Readme.md         | 38 +++++++++++++++++++
 docs/Recursion.md | 93 +++++++++++++++++++++++++++++++++++++++++++++++
 docs/Syntax.md    |  2 +-
 3 files changed, 132 insertions(+), 1 deletion(-)
 create mode 100644 docs/Recursion.md

diff --git a/Readme.md b/Readme.md
index 03d9ab2..a409f00 100755
--- a/Readme.md
+++ b/Readme.md
@@ -18,6 +18,44 @@ There are **no** functions in Meow. Instead, we have *macros*. A macro is a piec
 
 The only available data type is **String**. (However, you can encode other data types inside String)
 
+## Code Style
+
+Meow:
+
+```meow
+encode(s) {
+    var rep = {
+        "$" = "\$";
+        "#" = "\#";
+        "\" = "\\";
+        s
+    };
+    "#$"+ rep +"$#"
+}
+
+fib(x) {
+    if(
+        eq0(x),
+        0(),
+        if(
+            leq(x, 2()),
+            1(),
+            add(
+                fib(pred(x)),
+                fib(pred(pred(x)))
+            )
+        )
+    )
+}
+```
+
+Catlet (Compiled result):
+
+```catlet
+encode s = cat cat "#$" let "$" "\$" let "#" "\#" let "\" "\\" s "$#"
+fib x = if eq0 x 0 if leq x 2 1 add fib pred x fib pred pred x
+```
+
 ## Simple Start
 
 ```bash
diff --git a/docs/Recursion.md b/docs/Recursion.md
new file mode 100644
index 0000000..73cf14c
--- /dev/null
+++ b/docs/Recursion.md
@@ -0,0 +1,93 @@
+# Recursion
+
+It's possible to do recursion **as long as** we use the *by name* catlet interpreter.
+
+## Lazy (by name) evaluation
+
+For example,
+
+```meow
+take(x) {
+    "abc"
+}
+
+inf_loop() {
+    inf_loop()
+}
+
+test() {
+    take(inf_loop())
+}
+```
+
+In the above code, `inf_loop` will be evaluated to itself. However, `take` will only evaluate `inf_loop` when it is used. So `test` will not cause infinite loop.
+
+Moreover, the strict evaluation will not happen if the replacement is impossible. For example,
+
+```meow
+test() {
+    "abc" = inf_loop();
+    "xyz"
+}
+```
+
+In the above code, `inf_loop` will not be evaluated because the replacement is impossible.
+
+However, if you write the code like this:
+
+```meow
+test() {
+    inf_loop() = "abc";
+    "xyz"
+}
+```
+
+This will cause infinite loop.
+
+## Factorial
+
+Now we can write factorial.
+
+```meow
+factorial(x) {
+    if(
+        eq(x, 1()),
+        1(),
+        mul(
+            x,
+            factorial(pred(x))
+        )
+    )
+}
+```
+
+Compile result:
+
+```catlet
+factorial x = if eq x 1 1 mul x factorial pred x
+```
+
+## Fibonacci
+
+```meow
+fib(x) {
+    if(
+        eq0(x),
+        0(),
+        if(
+            leq(x, 2()),
+            1(),
+            add(
+                fib(pred(x)),
+                fib(pred(pred(x)))
+            )
+        )
+    )
+}
+```
+
+Compile result:
+
+```catlet
+fib x = if eq0 x 0 if leq x 2 1 add fib pred x fib pred pred x
+```
diff --git a/docs/Syntax.md b/docs/Syntax.md
index b33e08f..fdf7b74 100644
--- a/docs/Syntax.md
+++ b/docs/Syntax.md
@@ -44,7 +44,7 @@ Different to many languages, `X=Y` requires that both `X` and `Y` are **expressi
 
 The replacement **only** takes place in the `in xxx`. Hence, in `let X in (let Y in Z)`, the replacement of `X` only takes place in `Z` rather than `Y` (but there is a way to let it happen in `Y`, see later explanation).
 
-`MacroApplication` is a macro name followed by a list of arguments, like `succ(a,b,c)`. The language is *by value*, so the arguments are evaluated before the macro is applied.
+`MacroApplication` is a macro name followed by a list of arguments, like `succ(a,b,c)`. The language is *by name*, so the arguments will be evaluated after the macro is applied.
 
 ## Evaluation Mode