Aaditya-T/microProject-Sem1

This is a micro project made by me for first semester of Computer Engineering, Diploma at BBIT!

String Expression Calculator

This is a micro project made by Aaditya Thakkar.

main()

The main function is the entry point of the program and coordinates the overall flow of the program.

The algorithm works as follows:

1. Takes an input string from the user, and stores it in a variable.
2. Calls the tokenize function, passing the input string as an argument.
3. The tokenize function tokenizes the input string into an array of tokens, where each token is either an operator or an operand.
4. The main function calls the eval1 function passing the number of tokens as an argument.
5. The eval1 function evaluates the '^' and '!' operators by iterating through the tokens array from left to right and performs the power and factorial operation respectively on the operands that come before and after the operator. It also evaluates the brackets with the help of a temp array.
6. The main function calls the eval2 function passing the number of tokens as an argument.
7. The eval2 function evaluates the '*','/' and '%' operators by iterating through the tokens array from left to right and performs the multiplication, division and modulus operation respectively on the operands that come before and after the operator.
8. The main function calls the eval3 function passing the number of tokens as an argument.
9. The eval3 function evaluates the '+' and '-' operators by iterating through the tokens array from left to right and performs the addition and subtraction operation respectively on the operands that come before and after the operator.
10. Finally, the main function prints the final result of the evaluation.

tokenize() function -> int (numtokens)

The algorithm used in the tokenize function is a simple tokenizing algorithm that separates the input string into an array of tokens, where each token is either an operator or an operand.

The algorithm works as follows:

1. Initialize two variables, i and numBracks, to 0. i is used as an index for the tokens array, and numBracks is used to keep track of the number of brackets in the input string.
2. Use a while loop to iterate through the input string character by character.
3. Within the while loop, use the isdigit function to check if the current character is a digit. If it is, use the strtol function to convert the string of digits to a long integer and store the result in the tokens array.
4. If the current character is an operator (+, -, *, /, ^, !, %, (, or )), store the operator in the tokens array. Also, increment the numBracks variable if the operator is (.
5. If the current character is a space, ignore it and continue to the next character.
6. If the current character is any other type of character, print an error message and exit the program.
7. Continue the while loop until the end of the input string is reached.
8. After the while loop, check if the numBracks variable is greater than 1. If it is, print an error message and exit the program.
9. Finally, return the number of tokens in the tokens array.

This function returns the number of tokens present in the expression

eval() functions -> int (numtokens)

The algorithm used in the eval1, eval2, and eval3 functions is a simple left-to-right evaluation algorithm with operator precedence.

The algorithm works as follows:

1. eval1() function:

• Iterates through the tokens array from left to right.
• Looks for '^' and '!' operators.
• When it finds an operator, it performs the power and factorial operation respectively on the operands that come before and after the operator.
• The tokens array is updated by removing the operator and the right operand, and storing the result in the left operand.
• Additionally, this function also evaluates the brackets present in the expression first and then stores the result in the same array.

2. eval2() function:

• Iterates through the tokens array from left to right.
• Looks for '*','/' and '%' operators.
• When it finds an operator, it performs the multiplication, division and modulus operation respectively on the operands that come before and after the operator.
• The tokens array is updated by removing the operator and the right operand, and storing the result in the left operand.

3. eval3() function:

• Iterates through the tokens array from left to right.
• Looks for '+' and '-' operators.
• When it finds an operator, it performs the addition and subtraction operation respectively on the operands that come before and after the operator.
• The tokens array is updated by removing the operator and the right operand, and storing the result in the left operand.

The functions then print the updated tokens array and return the number of tokens. All the functions return the number of tokens left at the end of the process.