The interactive session
nx with no arguments at a terminal, or nx repl anywhere, opens a prompt:
Nexium 1.0.2 (nx repl, zig bundled with nx) on windows
Type :help for commands, :quit to exit.
> let xs = [3, 1, 2]
> import std.lists
> lists.max(i32, xs[..])
?i32: 3
> fn twice(x: i32) -> i32 { return x * 2 }
> twice(21)
i32: 42
> var s = String.from("nex")
> s.append("ium")
> s
String: "nexium"How it works#
Each line becomes part of a program: declarations (fn, struct, enum, import, ...) at the top level, everything else inside a main. The whole program is re-checked on every line, so the prompt reports exactly what the compiler would: type errors, effect violations, use after move. Only the new statements are executed, by the compiler's interpreter (the same one that runs comptime), against the values kept from earlier lines. A line that fails to check is not kept; a line that panics is reported and not kept.
An expression on its own prints its type and value. let and var bindings persist. Lines with unclosed brackets continue on the next prompt.
Commands#
| command | effect |
|---|---|
:help | the summary |
:quit, :q, exit | leave |
:vars | the kept bindings and their values |
:items | the declared items |
:load FILE | add the items of a file to the session |
:reset | start over |
Limits#
The interpreter covers the language but not the platform: @cImport calls, for parallel, using arena, and artifacts need a compiled program (nx run); the message names the expression that could not be evaluated. Values that only exist at compile time (function values, pointers) are not kept between lines. Speed is interpreted speed; measure with nx run.
In the session the program may do I/O (println, io.read_file, io.read_line, os.env, time.now, time.sleep), which comptime in a compiled program never may.