Command Processing System Explanation

Overview

The program is a text-based command processing system written in C that simulates buying and selling items, querying inventory, and tracking the location of people. It processes commands entered by the user and executes actions based on the given instructions.

Key Points

• The program uses a structured approach to process commands and manage inventories and locations.
• The functionality is flexible, supporting multiple actions, queries, and conditional statements.
• It efficiently validates user input and provides feedback if the commands are not correctly formatted.
• The test cases demonstrate the system's ability to handle complex interactions and maintain accurate inventory records.

Code Explanation

Header Inclusions and Definitions

The program includes several standard headers:

• stdio.h: For input/output operations.
• string.h: For string manipulation.
• stdlib.h: For dynamic memory management.
• ctype.h: For character handling.

Macros are defined to set limits for word lengths, number of words, keywords, and keyword lengths:

• MAX_WORD_LENGTH: Maximum length of a word.
• MAX_WORDS: Maximum number of words.
• NUM_KEYWORDS: Number of keywords used in commands.
• MAX_KEYWORD_LENGTH: Maximum length of a keyword.

Keyword Array

An array of 19 keywords is defined, such as "sell," "buy," "go," "to," "from," "and," etc. These keywords are essential for interpreting commands entered by the user.

Data Structures

• Item: Represents an item with a name and quantity.
• Subject: Represents a person with a name, location, previousLocation, inventoryCount, and an array of Item structures.
• Location: Represents a location with a name.

Global Variables

• people, locationlist, itemlist: Arrays to store people, locations, and items, respectively.
• locationcnt, itemcnt, people_count: Counters to track the number of locations, items, and people.

Helper Functions

• containsNumber and isFullNumber: Check if a string contains or is entirely composed of numbers.
• isIntheList: Checks if a string is present in a given list.
• isInKeywords: Checks if a string is a keyword.
• ifFinder, atFinder, hasFinder: Find the indices of keywords like "if", "at", and "has" in the word array.
• comparator: Compares two integers.
• findPerson and findPersonsItem: Find a person or an item in a person's inventory.
• buy and sell: Execute buying and selling operations for people and items.

Main Function

The main loop reads user input, tokenizes the input into words, and processes the commands.

• Validity Check: Validates the input command format and ensures that it follows the correct syntax and semantics.
• Question Processing: Handles queries about total items, locations, and inventory.
• Condition Handling: Evaluates conditional statements using "if", "at", and "has" for logical operations.
• Sentence Execution: Executes buy, sell, and go commands based on the parsed and validated input.

Test Cases and Outputs

Here are examples of test cases from the "input_01.txt" with commands and their expected outputs:

Some Test Cases from "input_01.txt"

Input:
Galadriel and Elrond and Cirdan buy 100 Nenya and 100 Narya and 100 Vilya

Output:
OK

Input:
Cirdan total ?

Output:
100 Nenya and 80 Vilya and 80 Narya

Input:
Balrog total ?

Output:
10 Narya and 10 Vilya

Input:
Balrog and Cirdan sell 10 Vilya to Legolas

Output:
OK

Input:
Balrog and Cirdan sell 10 Vilya to Legolas

Output:
OK

Input:
Balrog and Cirdan total Narya ?

Output:
90