Built-in Functions

Flexa provides a set of built-in functions that are always available, regardless of which libraries you import. These functions cover common tasks like input/output, string and array manipulation, and system operations. In this section, we’ll explore these functions and how to use them effectively.

Overview of Built-in Functions

Here are the main built-in functions in Flexa:

  1. print: Writes one or more values to the console without a newline.
  2. println: Writes one or more values to the console followed by a newline.
  3. read: Reads a line of input from the console; can optionally display one or more prompt messages.
  4. readch: Reads a single character from the console; can also accept prompt messages.
  5. len: Returns the length of a string or array.
  6. sleep: Pauses the program for a specified number of milliseconds.
  7. system: Executes a system command.

Using Built-in Functions

1. print

The print function writes a message to the console without adding a newline at the end.

Syntax

print(message);

Example

print("Hello, ");
print("Flexa!");
// Output: Hello, Flexa!

2. println

The println function writes a message to the console and adds a newline at the end.

Syntax

println(message);

Example

println("Hello, Flexa!");
// Output: Hello, Flexa! (followed by a newline)

3. read

The read function reads a line of input from the console.

Syntax

var input = read();

Example

println("Enter your name:");
var name = read();
println("Hello, " + name + "!");

4. readch

The readch function reads a single character from the console.

Syntax

var char = readch();

Example

println("Press any key:");
var key = readch();
println("You pressed: ", key);

5. len

The len function returns the length of a string or array.

Syntax

var length = len(value);

Example

var str = "Hello, Flexa!";
var arr = {1, 2, 3, 4, 5};

println("Length of string: ", len(str)); // Output: 13
println("Length of array: ", len(arr));  // Output: 5

6. sleep

The sleep function pauses the program for a specified number of milliseconds.

Syntax

sleep(milliseconds);

Example

println("Starting in 3 seconds...");
sleep(3000); // Pause for 3 seconds
println("Go!");

7. system

The system function executes a system command.

Syntax

var result = system(command);

Example

var result = system("ls -l"); // Lists files in the current directory (Unix-based systems)
println(result);

Input and Output with Multiple Parameters

The functions print, println, read, and readch in Flexa support zero or more arguments. This means you can pass any number of values to these functions, and they will automatically concatenate and format them.

This makes input and output highly flexible and convenient, especially for debugging or building dynamic messages.

Examples

println(); // Prints just a newline

println("Hello"); // Prints: Hello

println("Hello,", " ", "world!", 42); 
// Prints: Hello, world!42

var name = "John";
var age = 30;
print("Name: ", name, ", Age: ", age);
// Output: Name: John, Age: 30

var key = readch("Press any key to continue...");
println("You pressed:", " ", key);

You can also use read() without arguments for a prompt-less input:

var input = read(); // Waits for user input without printing anything

var response = read("Type something: ");
println("You typed:", response);

Examples of Built-in Functions

Example 1: Basic Input/Output

println("What is your name?");
var name = read();
println("Hello, " + name + "!");

println("Press any key to exit...");
var key = readch();
println("You pressed: " + key);

Example 2: Measuring Array Length

var numbers = {1, 2, 3, 4, 5};
println("The array has ", len(numbers), " elements.");

Example 3: Using sleep for Delays

println("Starting countdown:");
for (var i = 5; i >= 1; i--) {
  println(i);
  sleep(1000); // Wait 1 second
}
println("Blast off!");

Example 4: Executing System Commands

println("Listing files in the current directory:");
var result = system("dir"); // Windows
// var result = system("ls -l"); // Unix-based systems
println(result);

Best Practices

  1. Use println for Debugging: Use println to print debug messages during development. 
    println("Debug: Current value = " + value);
  2. Validate Input: Always validate input from the user to avoid unexpected behavior. 
    using flx.std.utils; // is_number

var age = read();
if (is_number(age)) {
  println("Your age is: ", age);
} else {
  println("Invalid input. Please enter a number.");
}

  3. Avoid Blocking Calls: Use sleep judiciously to avoid blocking the program for too long.

  4. Handle System Command Output: Be cautious when using system, as it executes commands directly on the operating system.

What’s Next?

Now that you’re familiar with the built-in functions, it’s time to explore advanced examples that combine multiple features of Flexa. Head over to the Advanced Examples section to see Flexa in action.

← Back to Built-in Libraries Next: Advanced Examples →