REPL

REPL

The dscript repl command starts an interactive read-eval-print loop backed by a persistent ScriptEngine. Variables, functions, and classes you declare in one line are available in all subsequent lines.

Running

dscript repl

Or via dotnet run:

dotnet run --project DScript.Cli -- repl

Session example

DScript 0.1.0 REPL  (type .exit to quit, .help for commands)

> var x = 10
> x + 5
15
> function square(n) { return n * n; }
> square(7)
49
> var nums = [1, 2, 3, 4, 5]
> nums.map(n => n * 2)
[ 2, 4, 6, 8, 10 ]
> .exit
bye.

How input is handled

The REPL distinguishes between statements and expressions:

• Lines that begin with var, let, const, function, or class, or that end with ;, are treated as statements and executed with engine.Execute(). No value is printed.
• Everything else is treated as an expression, evaluated with engine.EvalComplex(), and its result printed (unless the result is undefined).

This means you can omit the trailing semicolon when typing expressions you want to see the value of.

Built-in commands

Command	Description
.help	Show the list of REPL commands
.exit or .quit	End the session
Ctrl-C or Ctrl-D	End the session (EOF)

Standard library

The REPL loads DScript.Extras automatically, so console.log, Math, JSON, and all other standard-library globals are available immediately.

Persistent state

All globals survive across inputs within a single session. You can build up a script incrementally:

> function fib(n) { return n <= 1 ? n : fib(n-1) + fib(n-2); }
> fib(10)
55
> var result = fib(15)
> result
610

Error handling

Errors are caught and printed to stderr without ending the session:

> undeclaredVariable
Error: 'undeclaredVariable' is not defined
> 1 / 0
Infinity