Misconceptions

These are the misconceptions we collected so far in:

There is no connection between the number of misconceptions listed here and the difficulty of the corresponding programming language. The effort we spent on collecting misconceptions is very different for different languages. It would be inappropriate to reason about the quality of languages based on the number of misconceptions in this collection.

BaseCaseNotNeeded

Recursive computations do not necessarily need a base case

CompareBooleanToConstant

To test whether an expression evaluates to true or false, one must compare it to a constant

ConditionalIsSequence

If-then-else block is equivalent to sequence of two if-then blocks

ElseAlwaysExecutes

The else branch of an if-then-else block always executes

EqualityOperatorComparesListIdentities

(list a) = (list b) compares the identities of list a and list b

EqualityOperatorComparesOnlyTypes

() = () compares only the types of its operands

ExpressionAssigns

An expression that reads a variable also updates its value after the evaluation

ListLengthCannotBeZero

A list cannot have a length of 0 items

ListsHomogeneous

All items in a list must have the same type

MissingElseTerminates

Blocks following an if without else will not execute if the condition is false

RepeatDistributes

Each block in a loop is repeated individually

ResetStateEachLoopIteration

The computation of all loop iterations starts from the state before the loop

ResetStateEachProgramExecution

Running a Scratch program first resets the state of the world and then executes the program

Programming Language

Notional Machine

About This Site Contributors

Follow us on twitter to hear about new misconceptions.