Mastering Built-in Functions in REXX Programming Language: A Comprehensive Guide

Hello, fellow REXX enthusiasts! In this blog post REXX Built-in Functions guide, we will embark on an exciting journey into the world of a treas

ure trove of tools that can significantly enhance your programming efficiency and creativity. Built-in functions are pre-defined routines that perform specific tasks, saving you time and effort while writing code. Whether you’re manipulating strings, performing mathematical calculations, or handling input/output operations, REXX’s built-in functions are here to make your life easier. In this guide, we will explore the vast array of built-in functions available in REXX, categorize them for better understanding, and provide practical examples to demonstrate their usage. By the end of this post, you’ll have a solid grasp of how to leverage these powerful functions to write cleaner, more efficient, and dynamic REXX programs. So, let’s dive in and unlock the full potential of REXX built-in functions!

Introduction to Built-in Functions in REXX Programming Language

we’ll explore the world of Built-in Functions in the REXX programming language essential tools that enhance your productivity and streamline your coding experience. Built-in functions are pre-defined routines provided by the REXX language, designed to perform common tasks like string manipulation, mathematical computations, data conversion, and more. These functions save you time by eliminating the need to write complex logic from scratch. Whether you’re extracting substrings, formatting data, or performing arithmetic operations, REXX’s built-in functions provide a robust set of tools to simplify your programming. In this post, we’ll introduce you to the most widely used built-in functions, explain their syntax and use cases, and provide examples to help you understand how to leverage them effectively. By mastering these functions, you’ll unlock a deeper understanding of REXX’s capabilities, enabling you to write cleaner and more efficient code. Let’s dive in!

What are Built-in Functions in REXX Programming Language?

REXX (Restructured Extended Executor) is a high-level programming language designed for ease of learning and use. It provides numerous built-in functions that simplify tasks such as string manipulation, numerical operations, and data conversion. These built-in functions enhance productivity by reducing the amount of code required to perform common operations.

Here’s a detailed explanation of the categories of built-in functions in REXX:

String Manipulation Functions

String handling is a key feature of REXX, and it offers a variety of built-in functions to manipulate strings effectively.

• LEFT(string, length [, pad]): Extracts the leftmost characters of the specified length from a string. Optionally, you can add a pad character if the string is shorter than the specified length.
  • Example: LEFT('Hello', 3) → Hel
• RIGHT(string, length [, pad]): Extracts the rightmost characters of the specified length. Like LEFT, you can use a pad character.
  • Example: RIGHT('Hello', 4, '-') → -ello
• SUBSTR(string, start [, length [, pad]]): Extracts a substring starting at position start with an optional length and pad.
  • Example: SUBSTR('REXX Programming', 6, 11) → Programming
• LENGTH(string): Returns the length of the string.
  • Example: LENGTH('REXX') → 4
• POS(needle, haystack [, start]): Finds the position of a substring (needle) in a string (haystack), optionally starting from a specified position.
  • Example: POS('X', 'REXX') → 3
• WORD(string, n): Extracts the nth word from a string.
  • Example: WORD('REXX is easy', 2) → is
• STRIP(string [, option [, char]]): Removes leading, trailing, or both leading and trailing characters (char) from a string. Default option is ‘BOTH’ and default char is a space.
  • Example: STRIP(' REXX ') → REXX

Numerical and Arithmetic Functions

REXX supports arithmetic operations and numerical manipulations through these functions.

• ABS(number): Returns the absolute value of a number.
  • Example: ABS(-25) → 25
• MAX(num1, num2, …, numN): Returns the maximum value among the given numbers.
  • Example: MAX(10, 20, 15) → 20
• MIN(num1, num2, …, numN): Returns the minimum value among the given numbers.
  • Example: MIN(10, 20, 15) → 10
• ROUND(number, decimal_places): Rounds a number to the specified number of decimal places.
  • Example: ROUND(3.14159, 2) → 3.14
• TRUNC(number [, decimal_places]): Truncates a number to the specified number of decimal places.
  • Example: TRUNC(3.14159, 2) → 3.14

Data Conversion Functions

These functions help convert data types and values in REXX.

• FORMAT(number [, before [, after [, exponent]]]): Converts a number into a formatted string with optional specifications for decimal places, alignment, and exponent.
  • Example: FORMAT(123.456, 6, 2) → ' 123.46'
• D2X(number [, length]): Converts a decimal number to a hexadecimal representation, optionally specifying the length.
  • Example: D2X(255) → 'FF'
• X2D(hexadecimal): Converts a hexadecimal value back to a decimal.
  • Example: X2D('FF') → 255
• C2X(string): Converts a character string to its hexadecimal representation.
  • Example: C2X('AB') → '4142'
• X2C(hexadecimal): Converts a hexadecimal string back to its character representation.
  • Example: X2C('4142') → 'AB'

Logical and Comparison Functions

These functions allow comparisons and logical operations on data.

• COMPARE(string1, string2): Compares two strings lexicographically.
  • Example: COMPARE('abc', 'ABC') → 1 (Case-sensitive)
• DATATYPE(value [, type]): Determines if a value matches the specified data type (e.g., ‘NUM’, ‘CHAR’).
  • Example: DATATYPE('123', 'NUM') → 1
• SIGN(number): Returns -1, 0, or 1 depending on whether the number is negative, zero, or positive.
  • Example: SIGN(-25) → -1

Date and Time Functions

REXX can handle date and time-related operations using these functions.

• DATE([option]): Returns the current date in the specified format (option could be ‘S’, ‘E’, ‘B’, etc.).
  • Example: DATE('S') → 20250124 (Standard format)
• TIME([option]): Returns the current time in the specified format.
  • Example: TIME('L') → 12:34:56 (Local time)
• DELTA_TIME(start_time, end_time): Calculates the difference between two time values.

Miscellaneous Functions

These functions serve unique purposes.

• RANDOM(min, max [, seed]): Generates a random number within the specified range.
  • Example: RANDOM(1, 100) → Random number between 1 and 100.
• TRACE(setting): Enables or disables tracing of REXX instructions for debugging.
  • Example: TRACE('R') → Enables results tracing.
• SOURCELINE([line_number]): Returns the source line at the specified line_number in the program.
  • Example: SOURCELINE(1) → The first line of the program.
• VERSION(): Returns the version of the REXX interpreter being used.
  • Example: VERSION() → 'REXX-Regina_3.10'

Why do we need Built-in Functions in REXX Programming Language?

Built-in functions are a fundamental feature of the REXX (Restructured Extended Executor) programming language. They are pre-defined routines that perform specific tasks and return a value, making it easier to write efficient, readable, and maintainable code. Below is a detailed explanation of why built-in functions are essential in REXX, with each point explained in 4–5 lines and indexed for clarity.

1. Simplify Common Tasks

Built-in functions are designed to handle routine programming tasks, such as string manipulation, arithmetic operations, and input/output handling. Without these functions, you would need to write complex logic from scratch, which can be time-consuming and error-prone. For example, the LENGTH function calculates the length of a string in one line, eliminating the need for loops or custom logic.

2. Improve Code Readability

Using built-in functions makes your code more concise and easier to understand. The names of these functions often describe their purpose, making the code self-explanatory. For instance, UPPER("hello") clearly indicates that the string is being converted to uppercase, improving the clarity of your code.

3. Save Development Time

Built-in functions allow you to perform complex tasks with just a single line of code. This saves significant development time, as you don’t need to write and test custom logic for common operations. For example, generating a random number with RANDOM(1, 100) is much faster than implementing a random number generator from scratch.

4. Ensure Reliability and Accuracy

Built-in functions are part of the REXX language and are thoroughly tested and optimized. This ensures that they work correctly and efficiently, reducing the risk of errors in your code. For example, the SUBSTR function reliably extracts substrings without requiring manual boundary checks.

5. Enhance Productivity

By leveraging built-in functions, you can focus on solving higher-level problems rather than writing code for basic tasks. This enhances your productivity and allows you to build more complex and feature-rich programs. For instance, the LINEIN function simplifies file reading, letting you focus on processing the data.

6. Promote Code Reusability

Built-in functions are reusable components that can be used across multiple programs. This promotes code reusability and reduces duplication of effort. For example, the FORMAT function can be used in any program to format numbers consistently.

7. Handle Complex Operations Easily

Some tasks, such as formatting numbers or manipulating dates, can be complex to implement from scratch. Built-in functions simplify these tasks by providing ready-made solutions. For example, the DATE() function returns the current date in various formats, eliminating the need for custom date-handling logic.

8. Standardize Code

Using built-in functions ensures that your code follows a standard approach, making it easier for other developers to understand and maintain. For example, the LOWER function is a standard way to convert strings to lowercase, ensuring consistency across programs.

9. Reduce Code Complexity

Built-in functions help reduce the complexity of your code by encapsulating intricate logic into simple, easy-to-use routines. Instead of writing lengthy and complicated code for tasks like string manipulation or mathematical calculations, you can use a single function call. For example, the SUBSTR function extracts a substring in one line, avoiding the need for loops and conditional checks.

10. Facilitate Rapid Prototyping

Built-in functions enable rapid prototyping by allowing you to quickly implement and test ideas without spending time on low-level details. For instance, you can use the RANDOM function to generate test data or the DATE and TIME functions to add timestamps to your program outputs. This speeds up the development process and helps you iterate on your designs more efficiently.

Example of Built-in Functions in REXX Programming Language

REXX provides a rich library of built-in functions that simplify common programming tasks. Below are practical examples of built-in functions categorized by their functionality. Each example demonstrates how to use the function and includes the expected output.

1. String Manipulation Functions

Example LENGTH Function

The LENGTH function returns the length of a string.

text = "Hello, REXX!"
length = LENGTH(text)
SAY "Length of the string: " length  /* Output: Length of the string: 12 */

Example SUBSTR Function

The SUBSTR function extracts a substring from a string.

text = "Hello, REXX!"
substring = SUBSTR(text, 8, 4)  /* Extracts "REXX" */
SAY "Substring: " substring  /* Output: Substring: REXX */

Example UPPER and LOWER Functions

The UPPER function converts a string to uppercase, and the LOWER function converts it to lowercase.

text = "Hello, REXX!"
upper_text = UPPER(text)
lower_text = LOWER(text)
SAY "Uppercase: " upper_text  /* Output: Uppercase: HELLO, REXX! */
SAY "Lowercase: " lower_text  /* Output: Lowercase: hello, rexx! */

Example STRIP Function

The STRIP function removes leading and trailing spaces from a string.

text = "   Hello, REXX!   "
stripped_text = STRIP(text)
SAY "Stripped Text: '"stripped_text"'"  /* Output: Stripped Text: 'Hello, REXX!' */

 2. Arithmetic Functions

Example ABS Function

The ABS function returns the absolute value of a number.

num = -15
absolute_value = ABS(num)
SAY "Absolute Value: " absolute_value  /* Output: Absolute Value: 15 */

Example MAX and MIN Functions

The MAX function returns the larger of two numbers, and the MIN function returns the smaller.

num1 = 10
num2 = 20
max_num = MAX(num1, num2)
min_num = MIN(num1, num2)
SAY "Maximum: " max_num  /* Output: Maximum: 20 */
SAY "Minimum: " min_num  /* Output: Minimum: 10 */

Example RANDOM Function

The RANDOM function generates a random number between two specified values.

3. Input/Output Functions

Example LINEIN and LINEOUT Functions

The LINEIN function reads a line from a file, and the LINEOUT function writes a line to a file.

/* Writing to a file */
LINEOUT("output.txt", "Hello, REXX!")

/* Reading from a file */
line = LINEIN("output.txt")
SAY "File Content: " line  /* Output: File Content: Hello, REXX! */

4. Conversion Functions

Example DATE and TIME Functions

The DATE function returns the current date, and the TIME function returns the current time.

current_date = DATE()
current_time = TIME()
SAY "Today's Date: " current_date  /* Output: Today's Date: 28 Oct 2023 */
SAY "Current Time: " current_time  /* Output: Current Time: 14:35:10 */

Example FORMAT Function

The FORMAT function formats a number according to specified rules.

number = 123.456
formatted_num = FORMAT(number, 2)  /* Formats to 2 decimal places */
SAY "Formatted Number: " formatted_num  /* Output: Formatted Number: 123.46 */

5. Miscellaneous Functions

Example WORD and WORDS Functions

The WORD function extracts the nth word from a string, and the WORDS function returns the number of words in a string.

text = "REXX is a powerful language"
second_word = WORD(text, 2)  /* Extracts "is" */
word_count = WORDS(text)     /* Counts the number of words */
SAY "Second Word: " second_word  /* Output: Second Word: is */
SAY "Number of Words: " word_count  /* Output: Number of Words: 5 */

Example DELWORD Function

The DELWORD function deletes the nth word from a string.

text = "REXX is a powerful language"
new_text = DELWORD(text, 3)  /* Deletes the third word ("a") */
SAY "Updated Text: " new_text  /* Output: Updated Text: REXX is powerful language */

Putting It All Together: A Complete Example

Here’s a complete example that demonstrates the use of multiple built-in functions:

/* Complete Example: Using Built-in Functions */
text = "  REXX is fun!  "
num1 = -10
num2 = 25

/* String Manipulation */
SAY "Original Text: '"text"'"
SAY "Trimmed Text: '"STRIP(text)"'"  /* Removes leading/trailing spaces */
SAY "Uppercase: " UPPER(text)        /* Converts to uppercase */
SAY "Substring: " SUBSTR(text, 6, 5) /* Extracts "is fu" */

/* Arithmetic Operations */
SAY "Absolute Value of "num1": " ABS(num1)      /* Returns 15 */
SAY "Maximum of "num1" and "num2": " MAX(num1, num2)  /* Returns 20 */
SAY "Random Number between 1 and 100: " RANDOM(1, 100)

/* Conversion Functions */
SAY "Today's Date: " DATE()                   /* Returns current date */
SAY "Current Time: " TIME()                   /* Returns current time */
SAY "Formatted Number: " FORMAT(123.456, 2)   /* Returns 123.46 */

/* Miscellaneous Functions */
SAY "Number of Words: " WORDS(text)           /* Returns 5 */
SAY "Second Word: " WORD(text, 2)             /* Returns "is" */

Advantages of Built-in Functions in REXX Programming Language

These advantages make built-in functions indispensable in REXX programming, helping you write cleaner, more efficient, and maintainable code.

1. Simplify Common Tasks: Built-in functions handle routine tasks like string manipulation, arithmetic operations, and input/output handling. This eliminates the need to write complex logic from scratch, saving time and effort. For example, the LENGTH function calculates the length of a string in one line.
2. Improve Code Readability: Built-in functions make code more concise and easier to understand. Their names often describe their purpose, making the code self-explanatory. For instance, UPPER("hello") clearly indicates the string is being converted to uppercase.
3. Save Development Time: Built-in functions allow you to perform complex tasks with minimal code. This speeds up development, as you don’t need to write and test custom logic for common operations. For example, RANDOM(1, 100) generates a random number in one line.
4. Ensure Reliability and Accuracy: Built-in functions are part of the REXX language and are thoroughly tested and optimized. This ensures they work correctly and efficiently, reducing the risk of errors. For example, SUBSTR reliably extracts substrings without manual boundary checks.
5. Enhance Productivity: By leveraging built-in functions, you can focus on solving higher-level problems rather than writing code for basic tasks. This boosts productivity and allows you to build more complex programs. For instance, LINEIN simplifies file reading.
6. Promote Code Reusability: Built-in functions are reusable components that can be used across multiple programs. This reduces duplication of effort and promotes consistency. For example, the FORMAT function can format numbers in any program.
7. Handle Complex Operations Easily: Built-in functions simplify complex tasks like formatting numbers or manipulating dates. For example, the DATE() function returns the current date in various formats, eliminating the need for custom date-handling logic.
8. Standardize Code: Using built-in functions ensures your code follows a standard approach, making it easier for others to understand and maintain. For example, LOWER is a standard way to convert strings to lowercase.
9. Reduce Code Complexity: Built-in functions encapsulate intricate logic into simple routines, reducing code complexity. For example, SUBSTR extracts substrings without requiring loops or conditional checks.
10. Facilitate Rapid Prototyping: Built-in functions enable quick implementation and testing of ideas. For example, RANDOM can generate test data, and DATE/TIME can add timestamps, speeding up the development process.

Disadvantages of Built-in Functions in REXX Programming Language

These disadvantages highlight the limitations of built-in functions in REXX, emphasizing the need to balance their use with custom logic for more complex or specific tasks.

1. Limited Customization: Built-in functions are pre-defined and cannot be modified to suit specific needs. If a function does not fully meet your requirements, you may need to write additional code. For example, SUBSTR cannot handle advanced pattern matching or custom extraction rules.
2. Overhead in Learning: While built-in functions simplify coding, they require you to learn their syntax and behavior. Beginners may find it overwhelming to memorize the large number of functions and their parameters, such as the nuances of FORMAT or DATE.
3. Performance Overhead: Excessive or inappropriate use of built-in functions can introduce performance overhead. For example, repeatedly calling RANDOM in a loop for large datasets can slow down your program significantly.
4. Limited Functionality for Advanced Tasks: Built-in functions are designed for common tasks and may not support advanced or specialized operations. For instance, REXX lacks built-in functions for complex mathematical computations like matrix operations or statistical analysis.
5. Platform Dependency: Some built-in functions may behave differently across different implementations of REXX, such as IBM REXX or Open Object REXX. This can lead to compatibility issues when migrating code between platforms.
6. Lack of Flexibility: Built-in functions are rigid and cannot be extended or customized. If you need a function for a specific task not covered by built-in functions, you must write your own custom function, such as sorting arrays.
7. Debugging Challenges: Debugging can be challenging if a built-in function does not behave as expected. Since you cannot see the internal implementation, identifying the root cause of an issue may require extensive testing.
8. Limited Error Handling: Built-in functions may not provide detailed error messages or handling mechanisms. If a function fails or produces incorrect results, you may need to write additional code to handle errors, such as boundary checks for SUBSTR.
9. Over-reliance on Built-in Functions: Overusing built-in functions can lead to code that is difficult to maintain or optimize. For example, relying too heavily on UPPER or LOWER for case-insensitive comparisons may result in inefficient code.
10. Lack of Modern Features: REXX is an older language, and its built-in functions may lack modern features found in newer programming languages. For example, REXX does not have built-in support for regular expressions or advanced data structures like hash maps.

Future Development and Enhancement of Built-in Functions in REXX Programming Language

These future developments and enhancements would significantly improve the functionality, performance, and versatility of built-in functions in REXX, making it a more powerful tool for a wide range of programming tasks.

1. Support for Modern Data Structures: Future enhancements could include built-in functions for modern data structures like hash maps, sets, and dynamic arrays. This would make REXX more versatile for handling complex data manipulation tasks efficiently.
2. Advanced String Manipulation: Adding functions for advanced string operations, such as regular expressions, would greatly enhance REXX’s capabilities. This would allow for more powerful pattern matching and text processing.
3. Improved Mathematical Functions: Expanding the library to include advanced mathematical functions, such as matrix operations, statistical analysis, and numerical integration, would make REXX more suitable for scientific and engineering applications.
4. Enhanced Error Handling: Future versions could introduce more robust error-handling mechanisms within built-in functions. This would include detailed error messages and the ability to handle exceptions gracefully, improving debugging and reliability.
5. Cross-Platform Consistency: Ensuring that built-in functions behave consistently across different implementations of REXX (e.g., IBM REXX, Open Object REXX) would reduce compatibility issues and make it easier to migrate code between platforms.
6. Performance Optimization: Optimizing the performance of built-in functions, especially for large datasets and high-performance computing tasks, would make REXX more competitive with modern programming languages.
7. Integration with External Libraries: Enhancing REXX to better integrate with external libraries and APIs would expand its functionality. This could include built-in support for JSON, XML parsing, and web services.
8. User-Defined Function Enhancements: Allowing users to define and register their own functions as built-in functions would provide greater flexibility. This would enable developers to extend REXX’s capabilities without modifying the core language.
9. Improved Date and Time Functions: Adding more sophisticated date and time manipulation functions, such as time zone handling and calendar operations, would make REXX more useful for applications requiring complex date-time calculations.
10. Enhanced Input/Output Capabilities: Expanding the input/output functions to support more file formats, network communication, and real-time data processing would make REXX more adaptable to modern computing environments.