Question

(Postfix Evaluator Modification) Modify the postfix evaluator program of Exercise 22.13 so that it can process integer operands larger than 9

Short answer

To handle integer operands larger than 9, the Postfix Evaluator program needs to be modified to correctly parse multi-digit tokens, store larger integers, and accurately perform operations with them.

Step-by-step solution

Understand the Problem

The original Postfix Evaluator can only handle single-digit integers. The task is to modify the program to handle multi-digit integers.

Identify the Original Limitations

Identify why the original program is limited to single-digit integers. It may have to do with how the program parses input tokens or makes assumptions about the length of operands.

Modify Token Parsing

Adjust the program's parsing mechanism so that it can recognize multi-digit numbers as single tokens rather than individual characters.

Update Operand Storing

Make sure the data structure for storing operands can accommodate integers larger than 9.

Modify the Evaluation Algorithm

Update the algorithm responsible for performing operations so that it does not assume operands are single digits.

Test with Multi-Digit Operands

After modifying, test the program with multi-digit operands to ensure it evaluates them correctly.

Key concepts

Java Programming

Java programming is a foundational skill for creating a postfix evaluator. Understanding the language's syntax, data types, and methods is crucial for such a task. Java is widely known for its platform independence and object-oriented features, making it an excellent choice for developing reliable and maintainable applications. In the context of the given exercise, Java's robust standard library can greatly simplify the implementation of the evaluator by providing classes and methods to handle complex data structures and string manipulation, which are essential when dealing with token parsing and algorithm development.

Integer Operands

An integer operand in programming is a whole number that can be used in arithmetic operations. In the context of a postfix evaluator, operands are the data that need to be processed according to the operations specified in the postfix expression. Ensuring that the evaluator can handle integer operands larger than 9 is critical as it expands the evaluator's capabilities to process real-world problems where numbers are not restricted to single-digit values. This enhancement involves adjusting how the program reads and interprets strings of digits to maintain their sequence as a single integer value, rather than as separate tokens.

Algorithm Development

Algorithm development is key to creating an efficient and accurate postfix evaluator. It involves designing a step-by-step procedure to solve a particular problem, in this case, evaluating expressions written in postfix notation. Modifying the algorithm to handle integer operands larger than 9 requires thoughtful consideration of how the operands are stored and manipulated during the evaluation process. Ensuring that the data structure used to store the operands can handle larger and variable-sized integers without causing overflow or data loss is part of this development process.

Token Parsing

Token parsing is the process of breaking down a string of characters into meaningful pieces, or tokens, that a program can work with. In a postfix evaluator, tokens are generally operators like '+', '-', '*', '/', and operands which are the numbers. For the evaluator to process multi-digit integers correctly, it must effectively identify where one token ends and another begins. This may involve implementing a state machine within the parsing function or using regular expressions to match patterns that represent multi-digit integers, ensuring that these tokens are then correctly converted into numerical data types for further processing.

Data Structures

Data structures are essential for organizing and storing data in a program. In the case of postfix evaluation, a stack is typically the data structure of choice because it matches the last-in-first-out (LIFO) nature of postfix operations. When modifying the postfix evaluator to handle larger integers, it is crucial to ensure that the stack used can accommodate the expanded operand size. Depending on the language, this might involve using a stack of a larger or dynamic data type that can hold bigger numbers or objects if required.