REPL stands for “Read Eval Print Loop”. Basically it’s the console for evaluating Mwnci commands.
The REPL reads input, sends it to the interpreter for evaluation, prints the result/output of the interpreter and starts again. Read, Eval, Print, Loop.
To start with the REPL, just type mwnci and press enter
nobby@reggie> mwnci Mwnci 0.1.9.r14-20241208-042504 mwnci>
If all is well, then you will see something similar to the above, with the cursor waiting patiently at the end of mwnci>
We can now enter our first command, so we’ll start with the standard “Hello World”
Mwnci 0.1.9.r14-20241208-042504
mwnci> println("Hello World")
mwnci>
And majestically, another prompt appears. So where’s the output?
Due to a (very) bad decision by the author, a command or group of commands needs to be delimited by a colon (:) before anything is evaluated (executed).
Mwnci 0.1.9.r14-20241208-042504
mwnci> println("Hello World")
mwnci> :
Hello World
null
mwnci>
The last return value is also shown. In this case it’s null because the println command doesn’t need a return response other than output the requested text.
The colon doesn’t need to be on a separate line.
Mwnci 0.1.9.r14-20241208-042504
mwnci> println("Hello World")
mwnci> :
Hello World
null
mwnci> println("Hello World"):
Hello World
null
Now we can show how the colon works after entering several mwnci commands
mwnci> foreach n in 1..10 {
mwnci> println(n)
mwnci> }:
1
2
3
4
5
6
7
8
9
10
null
mwnci>
There is command line history for the REPL, using emacs bindings. So if you us the up arrow you can go back a line at a time. In this case a line is the succession of commands prior to the last colon. So if we press the up arrow you will see
mwnci> foreach n in 1..10 {
mwnci> println(n)
mwnci> }:
1
2
3
4
5
6
7
8
9
10
null
mwnci> foreach n in 1..10 { println(n) }
To exit the REPL and get back to the command line
mwnci> exit(): nobby@reggie>