From 252295fea959e7f37d06a53d693717e59b7ab7e8 Mon Sep 17 00:00:00 2001
From: xushiwei <x@goplus.org>
Date: Tue, 24 Sep 2024 19:34:52 +0800
Subject: [PATCH] mini spec: func

---
 doc/spec-mini.md | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/doc/spec-mini.md b/doc/spec-mini.md
index cef5cd4f6..565d73ddf 100644
--- a/doc/spec-mini.md
+++ b/doc/spec-mini.md
@@ -1686,7 +1686,26 @@ println
 
 ## Functions
 
-TODO
+A function declaration binds an identifier, the function name, to a function.
+
+```go
+FunctionDecl = "func" FunctionName Signature [ FunctionBody ] .
+FunctionName = identifier .
+FunctionBody = Block .
+```
+
+If the function's [signature](#function-types) declares result parameters, the function body's statement list must end in a [terminating statement](#terminating-statements).
+
+```go
+func IndexRune(s string, r rune) int {
+	for i, c := range s {
+		if c == r {
+			return i
+		}
+	}
+	// invalid: missing return statement
+}
+```
 
 ## Packages