Completion of def is_valid function
` ` ` PYTHON
# DO * NOT * WRITE YOUR NAME TO MAINTAIN ANONYMITY FOR PLAGIARISM DETECTION
# Prompts the user for an arity (a natural number) n and a word.
# Call the symbol a word consisting of nothing but alphabetic characters
# and underscores.
# Checks that the word is valid, in that it satisfies the following
# inductive definition:
# - a symbol, with Spaces charges at both ends, is a valid word.
# - a word of the form (w_1, s... , s w_n) denoting a symbol and
# w_1,... , w_n denoting valid words, with Spaces charges at both ends and
# around parentheses and commas, is a valid word.
The import sys
Def is_valid (word, arity) :
Return False
# REPLACE THE RETURN STATEMENT ABOVE WITH YOUR CODE
Try:
Arity=int (input (' input an arity: '))
If arity & lt; 0:
Raise ValueError
Except, ValueError:
Print (' Incorrect arity, giving up... ')
Sys. The exit ()
Word=input (' input a word: ')
If is_valid (word, arity) :
Print (' The word is valid.)
The else:
Print (' The word is invalid.)
` ` `
Example:
Quizzes 3
COMP9021 all OF PROGRAMMING
$python3 quiz_3. Py
Input an arity: 0
Input a word: f_1
The word is invalid.
$python3 quiz_3. Py
Input an arity: 0
Input a word: ()
The word is invalid.
$python3 quiz_3. Py
Input an arity: 0
Input a word: function_of_arity_one (hello)
The word is invalid.
$python3 quiz_3. Py
Input an arity: 1
Input a word: f)
The word is invalid.
$python3 quiz_3. Py
Input an arity: 1
Input a word: f [a]
The word is invalid.
$python3 quiz_3. Py
Input an arity: 2
Input a word: f (a, g, b))
The word is invalid.
$python3 quiz_3. Py
Input an arity: 3
Input a word: constant
The word is invalid.
$python3 quiz_3. Py
Input an arity: 3
Input a word: f ((a, b, c))
The word is invalid.
$python3 quiz_3. Py
Input an arity: 3
Input a word: f (g (a, a), f (a, b))
The word is invalid.
$python3 quiz_3. Py
Input an arity: 3
Input a word: f (g (a, b, c), g (a, b, c), g (a, b, c)
The word is invalid.
$python3 quiz_3. Py
Input an arity: 3
Input a word: f (a, g (a, b, f (a, b, c)), b, c)
The word is invalid.
Date: Term 3, 2020.
2 COMP9021 all OF PROGRAMMING
$python3 quiz_3. Py
Input an arity: 0
Input a word: a
The word is valid.
$python3 quiz_3. Py
Input an arity: 1
Input a word: function_of_arity_one (hello)
The word is valid.
$python3 quiz_3. Py
Input an arity: 2
Input a word: F (g (a, a), F (a, b))
The word is valid.
$python3 quiz_3. Py
Input an arity: 3
Input a word: ff (ff (ff (a, b, ff (aa, bb, cc)), b, ff (a, b, c)), b, ff (a, ff (a, b, c), c))
The word is valid.
$python3 quiz_3. Py
Input an arity: 4
Input a word: f (a, FF (a, b, FFF (a, b, c, and FfFf (a, b, c, d)), FfFf (a, b, c, d)), c, d)
The word is valid.
