"b" is for "bindings"

I'm learning Erlang. It's been fun! The Erlang shell is a great environment for poking around. You get there by typing erl into the terminal.

Erlang/OTP 24 [erts-12.0.3] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit] [dtrace]

Eshell V12.0.3  (abort with ^G)
1>

It might feel familiar if you've used the console in a web browser or a REPL in another language. Like the browser console, Erlang's shell environment includes handy shortcuts for shell-related activities. These are their stories.

"b" as in "bindings"

Variables in Erlang are immutable. You can't change 'em. I knew that going in, but it often trips me up in the shell.

1> One = 1.
1
2> Two = One + One.
2
3> One = 2.
** exception error: no match of right hand side value 2

Once you define a variable, you can't set it again. Immutable. Right. But sometimes, in a long shell session, I clear my screen or just forgot what variables I set.

Try b/0. It prints out all the variables defined in the current session along with their assigned values.

4> b().
One = 1
Two = 2
ok```

## "f" as in "forget"

Even better, `f/1` will _unbind_ a variable you want to reuse.

```erl-repl
12> b().
One = 1
Two = 2
ok
13> f(One).
ok
14> One = 2.
2

And if you need a clean slate, f/0 removes all variable bindings in the session.

16> b().
One = 2
Two = 2
ok
17> f().
ok
18> b().
ok

That's all for now. To learn more about the erlang shell, get straight into the docs.