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This program, as a whole, loads a bimmy++ program from a file on disk, and represents it as a Python list (or as an integer). Every program consists of a single expression, where an expression is either a list describing a computation that needs to be done, or an integer. If an expression is a computation, it will be a list of length 3. The first item in the list will be a string describing the computation to do -- either "add", "sub", "mul" or "div". The other two items in the list (at indices 1 and 2) will themselves be expressions in that same way. They might be integers, or they might be more computations that need to be done. (and so on, recursively!) So the two functions you need to finish are: 1. validate Takes anything at all (any Python value) and returns True if that value is a valid bimmy++ expression. A Python value is a valid bimmy++ expression if it is either an integer or a list describing a computation (in the way described above -- make sure to recursively check the children!). This function will always either return True or raise a ValueError. For style points (which don't affect your grade, just your reputation), put helpful error messages in your ValueError objects! 2. evaluate Takes a valid bimmy++ expression and evaluates it! (you only have to handle valid bimmy++ expressions here -- they have already been validated by validate, above) If the expression is an integer, just return that integer! If the expression describes a computation (ie, it is a list), then recursively evaluate its children (the operands for the computation). "add", "sub", and "mul" are pretty straightforward, but some care needs to be taken with "div". Make sure that "div" does integer division (use Python's // operator), and if you are about to divide by 0, raise a ValueError with the message "divide by zero".

This program, as a whole, loads a bimmy++ program from a file on disk, and represents it as a Python list (or as an integer). Every program consists of a single expression, where an expression is either a list describing a computation that needs to be done, or an integer. If an expression is a computation, it will be a list of length 3. The first item in the list will be a string describing the computation to do -- either "add", "sub", "mul" or "div". The other two items in the list (at indices 1 and 2) will themselves be expressions in that same way. They might be integers, or they might be more computations that need to be done. (and so on, recursively!) So the two functions you need to finish are: 1. validate Takes anything at all (any Python value) and returns True if that value is a valid bimmy++ expression. A Python value is a valid bimmy++ expression if it is either an integer or a list describing a computation (in the way described above -- make sure to recursively check the children!). This function will always either return True or raise a ValueError. For style points (which don't affect your grade, just your reputation), put helpful error messages in your ValueError objects! 2. evaluate Takes a valid bimmy++ expression and evaluates it! (you only have to handle valid bimmy++ expressions here -- they have already been validated by validate, above) If the expression is an integer, just return that integer! If the expression describes a computation (ie, it is a list), then recursively evaluate its children (the operands for the computation). "add", "sub", and "mul" are pretty straightforward, but some care needs to be taken with "div". Make sure that "div" does integer division (use Python's // operator), and if you are about to divide by 0, raise a ValueError with the message "divide by zero".

Database System Concepts
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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This program, as a whole, loads a bimmy++ program from a file on disk, and represents it as a Python list (or as an integer). Every program consists of a single expression, where an expression is either a list describing a computation that needs to be done, or an integer. If an expression is a computation, it will be a list of length 3. The first item in the list will be a string describing the computation to do -- either "add", "sub", "mul" or "div". The other two items in the list (at indices 1 and 2) will themselves be expressions in that same way. They might be integers, or they might be more computations that need to be done. (and so on, recursively!) So the two functions you need to finish are: 1. validate Takes anything at all (any Python value) and returns True if that value is a valid bimmy++ expression. A Python value is a valid bimmy++ expression if it is either an integer or a list describing a computation (in the way described above -- make sure to recursively check the children!). This function will always either return True or raise a ValueError. For style points (which don't affect your grade, just your reputation), put helpful error messages in your ValueError objects! 2. evaluate Takes a valid bimmy++ expression and evaluates it! (you only have to handle valid bimmy++ expressions here -- they have already been validated by validate, above) If the expression is an integer, just return that integer! If the expression describes a computation (ie, it is a list), then recursively evaluate its children (the operands for the computation). "add", "sub", and "mul" are pretty straightforward, but some care needs to be taken with "div". Make sure that "div" does integer division (use Python's // operator), and if you are about to divide by 0, raise a ValueError with the message "divide by zero".
Transcribed Image Text:This program, as a whole, loads a bimmy++ program from a file on disk, and represents it as a Python list (or as an integer). Every program consists of a single expression, where an expression is either a list describing a computation that needs to be done, or an integer. If an expression is a computation, it will be a list of length 3. The first item in the list will be a string describing the computation to do -- either "add", "sub", "mul" or "div". The other two items in the list (at indices 1 and 2) will themselves be expressions in that same way. They might be integers, or they might be more computations that need to be done. (and so on, recursively!) So the two functions you need to finish are: 1. validate Takes anything at all (any Python value) and returns True if that value is a valid bimmy++ expression. A Python value is a valid bimmy++ expression if it is either an integer or a list describing a computation (in the way described above -- make sure to recursively check the children!). This function will always either return True or raise a ValueError. For style points (which don't affect your grade, just your reputation), put helpful error messages in your ValueError objects! 2. evaluate Takes a valid bimmy++ expression and evaluates it! (you only have to handle valid bimmy++ expressions here -- they have already been validated by validate, above) If the expression is an integer, just return that integer! If the expression describes a computation (ie, it is a list), then recursively evaluate its children (the operands for the computation). "add", "sub", and "mul" are pretty straightforward, but some care needs to be taken with "div". Make sure that "div" does integer division (use Python's // operator), and if you are about to divide by 0, raise a ValueError with the message "divide by zero".
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