Pre- and Post-Conditions
Definition
Pre-conditions
The requirements that must be met before a function or algorithm is executed.
Definition
Post-conditions
The outcomes that must be true after the function or algorithm has completed.
- Pre-conditions describe the starting state before the execution of an algorithm.
- Post-conditions describe the final state after the execution of an algorithm.
- Cooking a meal
- Pre-condition: All ingredients are available.
- Post-condition: The meal is cooked and ready to be served.
- Calculating the square root
- Pre-condition: The input number is non-negative.
- Post-condition: The output is the square root of the input number.
Why Are Pre- and Post-Conditions Important?
In computer science, such conditions are helpful for:
- Algorithm design: Ensuring that each step of an algorithm is logically sound.
- Software development: Defining clear interfaces between modules or components.
- Testing and debugging: Identifying and fixing errors by verifying that pre- and post-conditions are met.
More examples
Pre-conditions:
- Mathematical Operations: Before calculating the square root of a number, a pre-condition might be that the input must be non-negative.
- Data Structures: When accessing an element in an array, a pre-condition could be that the index is within the array's bounds.
- Algorithmic Assumptions: A sorting algorithm might assume that the input is a list of comparable elements.
