Index: readme.txt
==================================================================
--- readme.txt
+++ readme.txt
@@ -39,6 +39,38 @@
 
 
 
 <<How to Use>>
 
-  I don't know.
+  > polemy
+      starts REPL
+
+  > polemy foo.pmy
+      executes foo.pmy
+
+
+
+<<Memo of Language Spec>>
+
+syntax
+
+ E ::= ("var"|"let"|"def"|LAYER) ID "=" E ; E
+     | "fun" "(" PARAMS ")" "{" E "}"
+     | E "(" ARGS ")"
+
+     | LAYER "(" E ")"
+
+     | "(" E ")"
+     | E BINOP E
+     | "if" "(" E ")" "{" E "}"
+     | "if" "(" E ")" "{" E "}" "else "{" E "}"
+     | ("var"|"let"|"def"|LAYER) ID "(" PARAMS ")" "{" E "}"
+
+ARGS ::= ","-separated E's
+PARAMS ::= ","-separated VAR's
+LAYER ::= "@" ID
+
+if-then-else is a syntax sugar for a function call: if( E, fun(){E}, fun(){E} )
+binary ops (e.g., E + E) is a syntax sugar: +(E, E)
+
+comment is "# ... \n"
+