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 a message to the console without a newline.
  2. println: Writes a message to the console with a newline.
  3. read: Reads a line of input from the console.
  4. readch: Reads a single character from the console.
  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);

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 →