category
arbitrary
Adds predicates for generating and shrinking random values for selected types to the library type object. User extensible.
logtalk_load(arbitrary(loader))static
Logtalk specific types:
entity,object,protocol,category,entity_identifier,object_identifier,protocol_identifier,category_identifier,event,predicate.Prolog module related types (when the backend compiler supports modules):
module,module_identifier,qualified_callable.Prolog base types:
term,var,nonvar,atomic,atom,number,integer,float,compound,callable,ground.Atom derived types:
non_quoted_atom,non_empty_atom,non_empty_atom(CharSet),boolean,character,in_character,char,operator_specifier,hex_char.Atom derived parametric types:
atom(CharSet),atom(CharSet,Length),non_empty_atom(CharSet),character(CharSet),in_character(CharSet),char(CharSet).Number derived types:
positive_number,negative_number,non_positive_number,non_negative_number.Float derived types:
positive_float,negative_float,non_positive_float,non_negative_float,probability.Integer derived types:
positive_integer,negative_integer,non_positive_integer,non_negative_integer,byte,in_byte,character_code,in_character_code,code,operator_priority,hex_code.Integer derived parametric types:
character_code(CharSet),in_character_code(CharSet),code(CharSet).List types (compound derived types):
list,non_empty_list,partial_list,list_or_partial_list,list(Type),list(Type,Length),list(Type,Min,Max),list(Type,Length,Min,Max),non_empty_list(Type),codes,chars.Difference list types (compound derived types):
difference_list,difference_list(Type).List and difference list types length: The types that do not take a fixed length generate lists with a length in the
[0,MaxSize]interval ([1,MaxSize]for non-empty list types).Predicate and non-terminal indicator types arity: These types generate indicators with an arity in the
[0,MaxSize]interval.Other compound derived types:
compound(Name,Types),predicate_indicator,non_terminal_indicator,predicate_or_non_terminal_indicator,clause,grammar_rule,pair,pair(KeyType,ValueType).Other types:
Object::Closure,between(Type,Lower,Upper),property(Type,LambdaExpression),one_of(Type,Set),var_or(Type),ground(Type),types(Types),types_frequency(Pairs),transform(Type,Closure),constrain(Type,Closure).Type
Object::Closurenotes: Allows calling public object predicates as generators and shrinkers. TheClosureclosure is extended with either a single argument, the generated arbitrary value, or with two arguments, when shrinking a value.Type
compound(Name,Types)notes: Generate a random compound term with the given name with a random argument for each type.Type
types_frequency(Pairs)notes: Generate a random term for one of the types in a list ofType-Frequencypairs. The type is randomly selected taking into account the types frequency.Type
transform(Type,Closure)notes: Generate a random term by transforming the term generated for the given type using the given closure.Type
constrain(Type,Closure)notes: Generate a random term for the given type that satisfy the given closure.Registering new types: Add clauses for the
arbitrary/1-2multifile predicates and optionally for theshrinker/1andshrink/3multifile predicates. The clauses must have a bound first argument to avoid introducing spurious choice-points.Shrinking values: The
shrink/3should either succeed or fail but never throw an exception.Character sets:
ascii_identifier,ascii_printable,ascii_full,byte,unicode_bmp,unicode_full.Default character sets: The default character set when using a parameterizable type that takes a character set parameter depends on the type.
Default character sets: Entity, predicate, and non-terminal identifier types plus compound and callable types default to an
ascii_identifierfunctor. Character and character code types default toascii_full. Other types default toascii_printable.Caveats: The type argument (and any type parameterization) to the predicates is not type-checked (or checked for consistency) for performance reasons.
Unicode limitations: Currently, correct character/code generation is only ensured for XVM and SWI-Prolog as other backends do not provide support for querying a Unicode code point category.
Public predicates
arbitrary/1
Table of defined types for which an arbitrary value can be generated. A new type can be registered by defining a clause for this predicate and adding a clause for the arbitrary/2 multifile predicate.
static, multifilearbitrary(Type)arbitrary(?callable) - zero_or_morearbitrary/2
Generates an arbitrary term of the specified type. Fails if the type is not supported. A new generator can be defined by adding a clause for this predicate and registering it via the arbitrary/1 predicate.
static, multifilearbitrary(Type,Term)arbitrary(::,*)arbitrary(@callable,-term) - zero_or_oneshrinker/1
Table of defined types for which a shrinker is provided. A new shrinker can be registered by defining a clause for this predicate and adding a definition for the shrink/3 multifile predicate.
static, multifileshrinker(Type)shrinker(?callable) - zero_or_moreshrink/3
Shrinks a value to a smaller value if possible. Must generate a finite number of solutions. Fails if the type is not supported. A new shrinker can be defined by adding a clause for this predicate and registering it via the shrinker/1 predicate.
static, multifileshrink(Type,Large,Small)shrink(@callable,@term,-term) - zero_or_moreshrink_sequence/3
Shrinks a value repeatedly until shrinking is no longer possible returning the sequence of values (ordered from larger to smaller value). Fails if the type is not supported.
staticshrink_sequence(Type,Value,Sequence)shrink_sequence(@callable,@term,-list(term)) - zero_or_oneedge_case/2
Table of type edge cases. Fails if the given type have no defined edge cases. New edge cases for existing or new types can be added by defining a clause for this multifile predicate.
static, multifileedge_case(Type,Term)edge_case(?callable,?term) - zero_or_moreget_seed/1
Gets the current random generator seed. Seed should be regarded as an opaque ground term.
staticget_seed(Seed)get_seed(-ground) - oneset_seed/1
Sets the random generator seed to a given value returned by calling the get_seed/1 predicate.
staticset_seed(Seed)set_seed(+ground) - onemax_size/1
User defined maximum size for types where its meaningful and implicit. When not defined, defaults to 42. When multiple definitions exist, the first valid one found is used.
static, multifilemax_size(Size)max_size(?positive_integer) - zero_or_oneProtected predicates
(no local declarations; see entity ancestors if any)
Private predicates
(no local declarations; see entity ancestors if any)
Operators
(none)
See also