Ideas.Common.Exercise

The Exercise record defines all the components that are needed for calculating feedback for one class of exercises. The fields of an exercise have to be consistent; consistency can be checked with the Ideas.Common.ExerciseTests module.

Exercise record

data Exercise a

For constructing an empty exercise, use function emptyExercise or makeExercise.

Constructors

NewExercise

Fields

exerciseId :: Id

Identifier that uniquely determines the exercise: see HasId for how to use values with identifiers.

status :: Status

The status of the exercise.

parser :: String -> Either String a

Parser for expressions of the exercise class, which either results in an error (Left) or a result (Right).

prettyPrinter :: a -> String

Pretty-printer for expressions of the exercise class. Pretty-printing should be the inverse of parsing.

equivalence :: Context a -> Context a -> Bool

Tests wether two expressions (with their contexts) are semantically equivalent. Use withoutContext for defining the equivalence check when the context is not relevant.

similarity :: Context a -> Context a -> Bool

Tests wether two expressions (with their contexts) are syntactically the same, or nearly so. Expressions that are similar must also be equivalent. Use withoutContext if the context is not relevant for the similarity check.

suitable :: Predicate a

Predicate suitable identifies which expressions can be solved by the strategy of the exercise class. It acts as the pre-condition of the strategy.

ready :: Predicate a

Predicate ready checks if an expression is in a solved form (accepted as a final solution). It acts as the post-condition of the strategy.

strategy :: LabeledStrategy (Context a)

The rewrite strategy that specifies how to solve an exercise.

canBeRestarted :: Bool

Is it possible to restart the rewrite strategy at any point in time? Restarting the strategy is needed when a student deviates from the strategy (detour). By default, restarting is assumed to be possible.

extraRules :: [Rule (Context a)]

Are there extra rules, possibly buggy, that do not appear in the strategy? Use ruleset to get all rules.

ruleOrdering :: Rule (Context a) -> Rule (Context a) -> Ordering

The rule ordering is a tiebreaker in situations where more than one rule can be used (e.g. feedback services onefirst and derivation; other feedback services return all possible rules).

navigation :: a -> ContextNavigator a

A navigator is needed for traversing the expression and for using the traversal strategy combinators. By default, an exercise has no navigator.

examples :: Examples a

A finite list of examples, each with an assigned difficulty.

randomExercise :: Maybe (StdGen -> Maybe Difficulty -> a)

A generator for random exercises of a certain difficulty.

testGenerator :: Maybe (Gen a)

An exercise generator for testing purposes (including corner cases).

hasTermView :: Maybe (View Term a)

Conversion to and from the (generic) Term datatype. Needed for representing the expression in the OpenMath standard.

hasTypeable :: Maybe (IsTypeable a)

Representation of the type of expression: this provides a back door for exercise-specific functionality.

properties :: Map String Dynamic

Extra exercise-specific properties, not used by the default feedback services.

Instances

Apply Exercise

Eq (Exercise a)

Ord (Exercise a)

HasId (Exercise a)

emptyExercise :: Exercise a

The emptyExercise constructor function provides sensible defaults for all fields of the Exercise record.

makeExercise :: (Show a, Eq a, IsTerm a) => Exercise a

In addition to the defaults of emptyExercise, this constructor sets the fields prettyPrinter, similarity, and hasTermView.

Convenience functions

prettyPrinterContext :: Exercise a -> Context a -> String

Pretty print a value in its context.

isReady :: Exercise a -> a -> Bool

Checks if an expression is in a solved form.

isSuitable :: Exercise a -> a -> Bool

Checks if the expression is suitable and can be solved by the strategy.

ruleset :: Exercise a -> [Rule (Context a)]

Returns a sorted list of rules, without duplicates.

getRule :: Monad m => Exercise a -> Id -> m (Rule (Context a))

Finds a rule of an exercise based on its identifier.

ruleOrderingWith :: HasId b => [b] -> Rule a -> Rule a -> Ordering

Makes a rule ordering based on a list of values with identifiers (e.g., a list of rules). Rules with identifiers that are not in the list are considered after the rules in the list, and are sorted based on their identifier.

Status

data Status

The status of an exercise class.

Constructors

Stable

A released exercise that has undergone some thorough testing

Provisional

A released exercise, possibly with some deficiencies

Alpha

An exercise that is under development

Experimental

An exercise for experimentation purposes only

Instances

Eq Status

Show Status

isPublic :: Exercise a -> Bool

An exercise with the status Stable or Provisional

isPrivate :: Exercise a -> Bool

An exercise that is not public

Examples

type Examples a = [(Difficulty, a)]

data Difficulty

Constructors

VeryEasy

Easy

Medium

Difficult

VeryDifficult

Instances

Enum Difficulty

Eq Difficulty

Data Difficulty

Ord Difficulty

Show Difficulty

Typeable * Difficulty

readDifficulty :: String -> Maybe Difficulty

Parser for difficulty levels, which ignores non-alpha charactes (including spaces) and upper/lower case distinction.

level :: Difficulty -> [a] -> Examples a

Assigns a difficulty level to a list of expressions.

mapExamples :: (a -> b) -> Examples a -> Examples b

examplesContext :: Exercise a -> Examples (Context a)

Returns the examples of an exercise class lifted to a context.

Context

inContext :: Exercise a -> a -> Context a

Puts a value into a context with an empty environment.

withoutContext :: (a -> a -> Bool) -> Context a -> Context a -> Bool

Function for defining equivalence or similarity without taking the context into account.

Type casting

useTypeable :: Typeable a => Maybe (IsTypeable a)

Encapsulates a type representation (use for hasTypeable field).

castFrom :: Typeable b => Exercise a -> a -> Maybe b

Cast from polymorphic type (to exercise-specific type). This only works if hasTypeable contains the right type representation.

castTo :: Typeable b => Exercise a -> b -> Maybe a

Cast to polymorphic type (from exercise-specific type). This only works if hasTypeable contains the right type representation.

Exercise properties

setProperty :: Typeable val => String -> val -> Exercise a -> Exercise a

Set an exercise-specific property (with a dynamic type)

getProperty :: Typeable val => String -> Exercise a -> Maybe val

Get an exercise-specific property (of a dynamic type)

Random generators

simpleGenerator :: Gen a -> Maybe (StdGen -> Maybe Difficulty -> a)

Makes a random exercise generator from a QuickCheck generator; the exercise generator ignores the difficulty level. See the randomExercise field.

useGenerator :: (Maybe Difficulty -> Gen a) -> Maybe (StdGen -> Maybe Difficulty -> a)

Makes a random exercise generator based on a QuickCheck generator for a particular difficulty level. See the randomExercise field.

randomTerm :: StdGen -> Exercise a -> Maybe Difficulty -> Maybe a

Returns a random exercise of a certain difficulty with some random number generator. The field randomExercise is used; if this is not defined (i.e., Nothing), one of the examples is used instead.

randomTerms :: StdGen -> Exercise a -> Maybe Difficulty -> [a]

Returns a list of randomly generated terms of a certain difficulty.

Derivations

showDerivation :: Exercise a -> a -> String

Shows the default derivation for a given start term. The specified rule ordering is used for selection.

showDerivations :: Exercise a -> a -> String

Shows all derivations for a given start term. Warning: there can be many derivations.

printDerivation :: Exercise a -> a -> IO ()

Prints the default derivation for a given start term. The specified rule ordering is used for selection.

printDerivations :: Exercise a -> a -> IO ()

Prints all derivations for a given start term. Warning: there can be many derivations.

diffEnvironment :: HasEnvironment a => Derivation s a -> Derivation (s, Environment) a

Adds the difference of the environments in a derivation to the steps. Bindings with identifier location are ignored. This utility function is useful for printing derivations.

defaultDerivation :: Exercise a -> a -> Maybe (Derivation (Rule (Context a), Environment) (Context a))

allDerivations :: Exercise a -> a -> [Derivation (Rule (Context a), Environment) (Context a)]