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tur repl — REPL Reference

tur repl launches an interactive Turmeric read-eval-print loop.

tur repl

Starting and stopping

$ tur repl
Turmeric v0.x.0  (type :help for help, :quit to exit)
>

Exit with :quit, :q, or Ctrl-D.

Evaluating expressions

Type any Turmeric expression and press Enter. The result is printed on the next line.

> (+ 1 2)
3
> (* 6 7)
42
> "hello"
"hello"

Top-level definitions persist across expressions:

> (defn square [x :int] :int (* x x))
> (square 9)
81

Multi-line input

If the parentheses in the current input are not balanced, the REPL keeps reading additional lines (shown with a indent prompt) until the expression is complete:

> (let [x 10
        y 20]
    (+ x y))
30

To abandon an incomplete expression, enter a blank line.

Meta-commands

Meta-commands begin with : and are processed before evaluation.

:help

Prints a summary of all meta-commands.

> :help
Meta-commands:
  :help               show this help
  :quit  :q           exit the REPL
  :type <expr>        print inferred type without evaluating
  :doc  <sym>         print documentation for a symbol or builtin
  :reload <file>      evaluate a .tur file into the current session

:quit / :q

Exits the REPL. Equivalent to Ctrl-D.

:type <expr>

Elaborates <expr> and prints the inferred type without evaluating it.

> :type (+ 1 2)
:int
> :type (fn [x :int] :int x)
(:int -> :int)

:doc <sym>

Prints brief documentation for a known builtin or user-defined symbol.

> :doc println
println — print a value followed by a newline
> :doc +
+ — integer or float addition

For user-defined functions the signature is printed:

> (defn square [x :int] :int (* x x))
> :doc square
square : (Int -> Int)

:reload <file>

Evaluates the contents of <file> into the current session. Useful for loading a script into the REPL without restarting.

> :reload src/utils.tur
reloaded src/utils.tur

If the file cannot be opened or contains an error, a diagnostic is printed and the session continues.

Output format

Value type Example output
Integer 42
Float 3.14
Boolean true / false
String (:cstr) "hello"
Nil (nothing printed — nil results are silent)
Closure #<fn square>
Struct #<struct Point>
Future #<future pending> / #<future resolved>
Error error: <message> (to stderr)

Colour output

ANSI colour is enabled automatically when both stdout and stderr are connected to a terminal. Diagnostics (type errors, parse errors) are highlighted in colour when enabled.

To force-disable colour, redirect output through a pipe:

tur repl 2>/dev/null | cat

Editing and history

If the binary was built with editline support (the default on macOS and most Linux distributions), the REPL provides:

Without editline, raw fgets input is used with no history or editing.

Non-interactive use

:reload can be piped in to run a script and then drop to the REPL, or to run a script non-interactively:

# Run a file and exit
printf ':reload myfile.tur\n:quit\n' | tur repl

# Capture output only (discard banner)
printf ':reload myfile.tur\n:quit\n' | tur repl 2>/dev/null \
    | sed '1d'   # strip the banner line

See also