I love the REPL in the Julia programming language. What makes me love it is combination of many small things which makes it practical: (1) remember past written

I love the REPL in the Julia programming language. What makes me love it is combination of many small things which makes it practical: (1) remember past written statements (2) completes both functions/types/variables and previously written statements (3) Whenever you write strings you get directory and file name completions. This is amazingly handy when doing some kind of scripting job. (4) The ability to jump into shell mode and help mode by just writing a single character. (5) The integration between the Julia REPL and Unix shell. When in shell mode my Julia variables are accessible as normal shell variables. It is really the combination of all these things which makes it feel very productive to work with.