Neon
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Advanced Features

1. Operator Overloading (Revisited)

You can override operators for containers (as shown earlier) and modules.

Example: Complex Numbers

# Define a Complex container
c1 = Complex(real: 1, imag: 2)
c2 = Complex(real: 3, imag: 4)

# Overload +
function Complex~add(a, b) do
    return (Complex(real: a>>real + b>>real, imag: a>>imag + b>>imag))
end

# Overload *
function Complex~mul(a, b) do
    realPart = a>>real * b>>real - a>>imag * b>>imag
    imagPart = a>>real * b>>imag + a>>imag * b>>real
    return (Complex(real: realPart, imag: imagPart))
end

# Now use overloaded operators
c3 = c1 + c2  # → Complex(4, 6)
c4 = c1 * c2  # → Complex(-5, 10)

2. Display Overloading

Override how containers are printed or converted to strings.

Example: Custom print for a Container

function Person~repr(p) do
    return (p>>firstName + " " + p>>lastName + " (" + str(p>>age) + ")")
end

alice = Person(firstName: "Alice", lastName: "Smith", age: 30)
print(alice)  # → "Alice Smith (30)"

3. The eval Function

Evaluates a string as Neon code and returns the result.

Example

result = eval("2 + 3 * 4")  # → 14
x = 10
result = eval("x * 2")       # → 20

Warning

4. The safeExec Function

Runs a Neon program in an isolated environment with given arguments.

Syntax

safeExec("filename.ne", [arg1, arg2, ...])

Example

safeExec("script.ne", ["arg1", 42])

5. The ~ Character in Modules

6. The help Function

Get information about objects, modules, or variables.

Examples

help("modules")      # List all modules
help("variables")    # List all variables and their types
help("Math")         # List all objects in the Math module
help(add)           # Show help for the add function
help(42)            # Show type of 42 (Integer)

7. Graphics (TI-EZ80 Only)

Neon provides a graphics extension for TI-EZ80 calculators (TI-83 Premium CE, TI-84 Plus CE).

Initialization

init(Graphics)  # Must be called first

Predefined Container Types

Type Fields Description
Point x, y A point on a polygon outline.
Circle x, y, r (radius), c (color), f (filled) A circle.
Rect x, y, w (width), h (height), c (color), f (filled) A rectangle.
Line x0, y0, x1, y1, c (color) A line.
Text t (text), x, y, fg (foreground color), bg (background color), s (size) Text.
Triangle x0, y0, x1, y1, x2, y2, c (color) A triangle (always filled).
Polygon p (points), c (color) A polygon (list of Points).
Ellipse x, y, a, b, c (color), f (filled) An ellipse (a = horizontal radius, b = vertical radius).
FloodFill x, y, c (color) Fills an area with a color.

Colors

Example: Drawing Shapes

init(Graphics)

# Draw a red circle
circle = Circle(x: 100, y: 100, r: 50, c: rgb(255, 0, 0), f: True)
draw(circle)

# Draw a green rectangle
rect = Rect(x: 50, y: 50, w: 80, h: 40, c: rgb(0, 255, 0), f: False)
draw(rect)

# Draw a line
line = Line(x0: 0, y0: 0, x1: 319, y1: 239, c: rgb(0, 0, 255))
draw(line)

# Draw text
text = Text(t: "Hello, Neon!", x: 10, y: 20, fg: rgb(255, 255, 255), bg: rgb(0, 0, 0), s: 1)
draw(text)

Keyboard Input

Use getKey() to read key presses.

Key Codes (TI-EZ80)

Example: Simple Game Loop

init(Graphics)

# Player position
playerX = 100
playerY = 100

while (True) do
    # Clear screen (draw a black rectangle)
    draw(Rect(x: 0, y: 0, w: 320, h: 240, c: 0, f: True))

    # Draw player (white circle)
    draw(Circle(x: playerX, y: playerY, r: 10, c: rgb(255, 255, 255), f: True))

    # Handle input
    key = getKey()
    if (key == 24) then  # 7 key
        playerY -= 5
    elif (key == 25) then  # 8 key
        playerY += 5
    elif (key == 33) then  # 2 key
        playerX -= 5
    elif (key == 34) then  # 3 key
        playerX += 5
    elif (key == 41) then  # ON key
        break
    end

    # Keep player on screen
    if (playerX < 0) then playerX = 0 end
    if (playerX > 319) then playerX = 319 end
    if (playerY < 0) then playerY = 0 end
    if (playerY > 239) then playerY = 239 end

end

8. File I/O

Neon provides functions to read and write files.

Functions

Function Description
readFile(filename) Reads a file and returns its content as a string.
writeFile(filename, content) Writes a string to a file (overwrites if exists).
detectFiles(prefix) Returns a list of filenames whose contents begin with prefix.

Example

# Write to a file
writeFile("hello.txt", "Hello, Neon!")

# Read from a file
content = readFile("hello.txt")
print(content)  # → "Hello, Neon!"

# List files starting with "data"
files = detectFiles("data")
print(files)  # e.g., ["data1.txt", "data2.txt"]

On TI-EZ80

9. Special Variables and Constants

Variable Description
Pi The mathematical constant π (~3.14159).
__name__ "__main__" in the main script, otherwise the filename.
__platform__ Platform ("LINUX_AMD64", "WINDOWS_AMD64", "TI_EZ80").
__version__ Neon interpreter version.
__args__ List of command-line arguments (in execution mode).
Ans Last result in console mode.

Example

print("Running on " + __platform__)
print("Neon version: " + __version__)
print("Pi: " + str(Pi))

10. The setColor Function

Change the text color in the console.

Example

setColor("red")
print("This is red text!")
setColor("blue")
print("This is blue text!")
setColor("default")  # Reset to default

Best Practices

  1. Use meaningful variable names:

    # Bad
x = 10
y = 20

# Good
width = 10
height = 20

  2. Comment your code:

    # Calculate the sum of a list
function sumList(lst) do
    total = 0
    foreach (num, lst) do
        total += num
    end
    return (total)
end

  3. Use functions to avoid repetition:

    # Bad (repeated code)
print("Hello, Alice!")
print("Hello, Bob!")

# Good
function greet(name) do
    print("Hello, " + name + "!")
end
greet("Alice")
greet("Bob")

  4. Handle errors gracefully:

    try
    result = 10 / 0
except (DivisionByZero) do
    print("Error: Division by zero!")
end

  5. Use local() to avoid side effects:

    function safeModify(x) do
    local(x)  # Prevents modifying global x
    x += 1
    return (x)
end

  6. Use await() for passive waiting in concurrent code:

    # Bad (active waiting)
while (not condition) do
    pass
end

# Good (passive waiting)
await(condition)

  7. Use atomic blocks for thread-safe operations:

    atomic
    sharedCounter += 1
end

  8. Organize code into modules:

    # In math.ne
function Math~add(a, b) do
    return (a + b)
end

# In main.ne
import "math"
result = Math~add(2, 3)

Exercises

Beginner

  1. Write a program that prints the sum of two numbers entered by the user.
  2. Write a function isEven(n) that returns True if n is even, False otherwise.
  3. Write a loop that prints the first 10 Fibonacci numbers.
  4. Write a program that checks if a word is a palindrome (e.g., "radar").

Intermediate

  1. Write a function factorial(n) that calculates the factorial of n (recursively or iteratively).
  2. Write a program that finds the largest number in a list.
  3. Write a function reverseString(s) that reverses a string without using the reverse function.
  4. Write a program that counts the number of vowels in a string.

Advanced

  1. Write a recursive function to calculate the nth Fibonacci number.
  2. Write a program that sorts a list of numbers (implement bubble sort or quicksort).
  3. Write a concurrent program that calculates the sum of numbers from 1 to 1000 in parallel (split the work between 2 processes).
  4. Write a module for a Vector2D container with add, sub, and mul (scalar multiplication) operations.
  5. Write a TI-EZ80 graphics program that draws a bouncing ball.
  6. Write a program that reads a file, counts the number of words, and writes the result to another file.

Resources

Congratulations! You’ve now learned the fundamentals (and advanced features) of the Neon programming language. Happy coding!

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