Readme added

Added a Readme file

diff --git a/Readme.md b/Readme.md
new file mode 100644 (file)
index 0000000..69a2db1
--- /dev/null
+++ b/Readme.md
@@ -0,0 +1,28 @@
+# evpf - postfix evaluator
+
+evpf (**ev**aluate **p**ost**f**ix is a simple postfix expression evaluator
+written as a learning project in rust. It supports both command line and 
+interactive mode.
+
+## Command line mode
+
+    evpf <expression>
+
+where `<expression>` is a postfix expression like `20 30 + 11 -` etc. 
+Currently only 4 operators are supported: `+`, `-`, `*` and `/`. (In command
+line mode, `*` has to be escaped using `\*` to work properly.)
+
+## Interactive mode
+
+Interactive mode displays a prompt where expressions can be evaluated by 
+typing into the prompt (line editing and session-history supported by 
+`rustyline`. 
+
+    evpf> 
+
+In interactive mode, apart from entering expressions, the following commands 
+are supported
+
+* `q` or `Q` - quit
+* `?` or `h` or `H` - help
+