Benky

Benky is a small programming language with its own lexer, parser, and interpreter, written in Dart. Programs are saved as .benky files and run with the benky command-line tool.

benky run main.benky

---

Installation

There are two roles here: building the benky tool, and using it. You only need Dart for the first one.

Option A — Build it yourself (you need Dart once)

1. Install the Dart SDK: https://dart.dev/get-dart

2. From the project folder:

   dart pub get
   dart compile exe bin/benky.dart -o benky

   This produces a single standalone native executable called benky (or benky.exe on Windows). It does not require Dart to run — the Dart runtime is statically baked into the binary. You can copy this one file to any machine of the same OS/architecture and it will run with nothing else installed.

3. Put it on your PATH so you can call it from anywhere:

   • macOS/Linux: sudo mv benky /usr/local/bin/benky
   • Windows: move benky.exe into a folder that's on your PATH (e.g. C:\Tools\, then add that folder to PATH via System Settings → Environment Variables).

Option B — Just use the compiled exe (no Dart needed)

If someone hands you the benky (or benky.exe) binary directly — no Dart SDK, no pub get, nothing else to install. Just:

benky run main.benky

That's the whole point of compiling it with dart compile exe: it's a real, independent compiler/runtime in one file, the same way a C program compiles to an .exe that doesn't need a C compiler to run.

---

Usage

benky run main.benky          # run a benky program

Errors print to stderr with a line number and a non-zero exit code (65 for syntax errors, 70 for runtime errors).

---

Language syntax

Comments

# everything after a # to end of line is a comment

Variables

let x = 5          # declare (required before use)
x = x + 1           # reassign

Literals

5            # number (stored as a double)
3.14
"hello"      # string — supports escapes: \n \t \r \" \\
true
false

Operators

+  -  *  /  %        # arithmetic (+ also concatenates strings)
==  !=               # equality
<  >  <=  >=         # comparison
=                    # assignment
-x                   # unary negation
( )                  # grouping

print

print "hello"
print "line one\nline two"

if / else / else if

if x > 4 {
  print "big"
} else if x > 0 {
  print "medium"
} else {
  print "small"
}

while loops

let i = 0
while i < 3 {
  print i
  i = i + 1
}

Functions

fun add(a, b) {
  return a + b
}

let result = add(2, 3)

return with no value ends the function early.

throw

fun divide(a, b) {
  if b == 0 {
    throw "cannot divide by zero"
  }
  return a / b
}

Throwing prints Uncaught error: <value> and exits the program with code 70. There is no try/catch yet — every throw is unrecoverable.

Built-in functions

Function	Description
len(s)	length of a string
str(v)	convert a value to a string
num(s)	parse a string into a number
http_get(url)	blocking HTTP GET, returns the response body as a string

Terminal UI built-ins

These draw directly into the terminal window using ANSI escape codes — no GUI window, just live text drawn in your existing cmd/terminal.

Function	Description
ui_clear()	clear the screen
ui_hide_cursor() / ui_show_cursor()	toggle cursor visibility
ui_text(x, y, text, color?)	print text at a position (supports \n for multi-line)
ui_box(x, y, w, h, title?, color?)	draw a bordered box
ui_button(x, y, label, color?)	draw a [ label ] button (visual only — no click handling)
ui_input(x, y, prompt?)	blocking read of a line of input at a position

Valid color names: black red green yellow blue magenta cyan white.

Example:

ui_clear()
ui_box(2, 1, 40, 5, "My App", "cyan")
ui_text(5, 3, "Hello there!", "green")
let name = ui_input(2, 6, "Name: ")
ui_text(2, 8, "Hi, " + name + "!", "magenta")

---

What's not in Benky yet

No lists/arrays, no maps/objects, no classes, no for loops, no &&/|| logical operators, no try/catch, no modules/imports, no closures over outer function scopes (functions only see globals

• their own locals). These are the natural next features if you want to keep growing the language.

---

Project layout

benky/
  bin/benky.dart            CLI entry point ("benky run main.benky")
  lib/src/token.dart        token definitions
  lib/src/lexer.dart        text -> tokens
  lib/src/ast.dart          AST node classes
  lib/src/parser.dart       tokens -> AST
  lib/src/interpreter.dart  walks the AST and executes it
  lib/src/ui.dart           terminal UI drawing primitives
  main.benky                example program