Given the following definition of doubleEvens

when you invoke it as follows

what is the result?

Question

Given the following definition of doubleEvens

when you invoke it as follows

what is the result?

BlackTom AI · Accepted Answer

Let's walk through how doubleEvens processes the input step by step so each option can be evaluated clearly.
Option 1: "[2, 4, 6, 8]". This would be the result if we mapped x * 2 over the entire input list without filtering out odd numbers first. Since the function filters even numbers only, this would be incorrect because 1 and any odd elements would still be present in the input, and their doubling would not be produced in this ordering. Therefore, this option misrepresents the effect of the filter stage.
Option 2: "[4, 8]". The function first filters the list to keep elements where x mod 2 == 0, i.e., the even numbers. Starting with [1, 2, 3, 4], the filter yields [2, 4]. Then the map (\x -> x * 2) is applied to that filtered list, producing [4, 8]. This matches the sequential application of filter followed by map exactly, so this option is a correct representation of the result.
Option 3: "[1, 2, 3, 4]". This would occur if we mapped x * 2 over the original list, or if there were no transformations at all. Neither is the case here, because the filter removes odd numbers before mapping, so the original list cannot survive intact to the output. Hence this option is incorrect.
Option 4: "map doesn't have enough arguments error". The lambda in map has a well-formed single-argument function (\x -> x * 2) and map is applied to the list produced by filter. There is no arity error in this expression; the code typechecks and evaluates to a list. Therefore, this option describes a runtime or type error that does not occur here and is incorrect.

CPT_S-355-PULLM-1-LEC Scheduled Quiz 1

Given the following definition of doubleEvens when you invoke it as follows what is the result?

View Explanation

Log in for full answers

Similar Questions

Question at position 11 Given the following Haskell expression Which of the following expressions is equivalent to the above, using the $ operator to reduce parentheses? Clear my selection

Question at position 7 Given the following Haskell function: Which one of the following expressions correctly applies increment to a value of type Maybe Int? Clear my selection

Question at position 3 A programming language must have static typing to support functional programming.TrueFalse

"You cannot use iteration constructs (for, while, do-while) in a purely functional programming language. (ex: Haskell)" True or False?

Given the following definition of 'sqr' and 'res1' How many times was 'sqr' called to compute 'res1'? Note: 'even' is an inbuilt function which returns true if the argument is an even number

Given the following definition of computeList When you invoke it as follows What is the result?

More Practical Tools for Students Powered by AI Study Helper

Homework AI Solver

Stylized AI Paper Writer

Plagiarism Checker Assistant

Citation AI Academic Writing Tool

In-Class Translation Assistant

AI Note Generator

AI Quiz Answers

Past Exam Questions from University Test Bank

Smart Practice Assistant

Adaptive Practice

Making Your Study Simpler