Name

SPVM::Document::Language::Types - Types in the SPVM Language

Description

This document describes types in the SPVM language.

Data

This section describes data.

A data is called value.

Number

The value of numeric types is called number.

Normally, numbers are created by numeric literals.

  # byte - 8bit signed integer
  my $number = (byte)1;
  
  # short - 16bit signed integer
  my $number = (short)1;
  
  # int - 32bit signed integer
  my $number = 1;
  
  # long - 64bit signed integer
  my $number = 1L;
  
  # float - 32bit floating point
  my $number = 1.5f;
  
  # double - 64bit floating point
  my $number = 1.0;

A character created by the character literal is a number of the byte type.

  # A number of the byte type created by a character literal
  my $char = 'a';

See the following section operations for numbers.

• Numeric Operators

• Numeric Comparison Operators

Internal Representation of Negative Integers

Negative integers are represented by two's complement.

String

The value of the string type is called string.

A string consists of characters of the byte type.

A string has its length.

A string is an object.

Normally, a string is created by a string literal or the new_string_len operator.

  # A string created by a string literal
  my $string = "Hello";
  my $char = $string->[0];
  
  # A mutable string created by the new_string_len operator
  my $string = new_string_len 3;
  $string->[0] = 'a';

See the following sections about operations for strings.

• length Operator

• String Concatenation Operator

• Getting a Character

• Setting a Character

• new_string_len Operator

• make_read_only Operator

• is_read_only Operator

• String Comparison Operators

• copy Operator

Sting Native Level Representation

At the native level, the character just after the last character of the string is set to \0, so the characters in the string can be used as a C language string.

  # The characters in the string can be used as a C language string
  void* obj_string = stack[0].oval;
  const char* chars = env->get_chars(env, stack, obj_string);
  if (strcmp(chars, "Hello") == 0) {
    
  }

Array

The value of an array type is called array.

An array consists of a set of numbers, a set of objects, or a set of multi-numeric numbers.

An array has its length.

The elements of an array are arranged by index and the index starts from 0.

An array is an object.

Normally, an array is created by the new Operator and an array initialization.

  # An array created by the new operator
  my $numbers = new int[3];
  $numbergers->[0] = 1;
  
  my $strings = new string[3];
  
  my $objects = new Point[3];
  
  my $mulnum_numbers = new Complex_2d[3];
  
  # An array created by an array initialization
  my $numbers = [1, 2, 3];

All elements of an array can be got by the for statement.

  # for statement
  for (my $i = 0; $i < @$numbers; $i++) {
    my $number = $numbers->[$i];
  }
  
  # for-each statement
  for my $number (@$numbers) {
    
  }

See the following sections about operations for arrays.

• Creating Array in new Operator

• Array Initialization

• Array Length Operator

• Getting an Array Element

• Setting an Array Element

Object

The value of an object type is called object.

A string is an object.

An array is an object.

An objcet of the class type has its fields. A field is a number or an object.

Normally, an object is created by the new operator.

  # An object created by the new operator
  my $point = new Point;

When an object is created, memory for the object is allocated in heap memory.

Created objects are destroyed by garbage collection.

See the following sections about operations for objects.

• new Operator

• dump Operator

• Getting a Field

• Setting a Field

• isa Operator

• is_type Operator

• type_name Operator

Object Native Level Representation

At native level, an object is a memory address.

  void* obj_point = stack[0].oval;

Undefined Value

The value of the undef type is called undefined value.

An undefined value means the value is undefined.

An undefined value is created by the undef operator.

  undef

An undefined value is able to be assigned to an object type.

  my $point : Point = undef;

Examples:

  # Examples of undefined values
  my $string : string = undef;
  
  if (undef) {
    
  }
  
  my $message = "Hello";
  if ($message == undef) {
    
  }

Undefined Value Native Level Representation

At native level, an undefined value is equal to 0, normally a null pointer NULL defined in stddef.h.

  NULL

Multi-Numeric Number

The value of a multi-numeric type is called multi-numeric number.

A multi-numeric number is a set of numbers of the same type.

  my $z : Complex_2d;
  $z->{re} = 1;
  $z->{im} = 2;

See the following sections about operations for multi-numeric numbers.

• Getting a Multi-Numeric Field

• Setting a Multi-Numeric Field

Reference

The value of a reference type is called reference.

A reference has a referencing value.

A referencing value must be a number or a multi-numeric number

The reference operator \ creates a reference.

  my $number : int;
  my $number_ref = \$number;

See the following sections about operations for multi-numeric numbers.

• Getting a Referenced Value

• Setting a Referenced Value

• Reference Operator

• Dereference Operator

• Getting a Referenced Multi-Numeric Field

• Setting a Referenced Multi-Numeric Field

Reference Native Level Representation

At native level, a reference is a memory address.

  int32_t* num_ref = stack[0].iref;

Types

This section describes types.

Numeric Types

This section describes numeric types.

Integer Types

This section describes integer types.

An interger type is a numeric type.

byte Type

The byte type is the type for a signed 8-bit integer.

  byte

The byte type is an integer type.

short Type

The short type is the type for a signed 16-bit integer.

  short

The short type is an integer type.

int Type

The int type is the type for a signed 32-bit integer.

  int

The int type is an integer type.

long Type

The long type is the type for a signed 64-bit integer.

  long

The long type is an integer type.

Floating Point Types

This section describes floating point types.

A floating point type is a numeric type.

float Type

The float type is the type for 32bit floating point.

  float

The float type is a floating point type.

double Type

The double type is the type for 64bit floating point.

  double

The double type is a floating point type.

Numeric Types Order

numeric types have its order.

The order is byte, short, int, long, float, double from smallest to largest.

Object Types

This section lists object types.

string Type

The string type is the type for strings.

  string

The string type is an object type.

The string type can be qualified with the mutable type qualifier.

  mutable string

Class Types

A class type is the type for a class.

A class type is defined by class definition.

  class CLASS_TYPE {
  
  }

An object can be created from a class by a new operator.

Note that an interface type and a multi-numeric type is not a class type although these types are defined by class definition.

Numeric Object Types

A numeric object type is a class type that owns the corresponding field of a numeric type.

The List of Numeric Object Types:

Numeric Object Types	Corresponding Numeric Types
Byte	byte
Short	short
Int	int
Long	long
Float	float
Double	double

Interface Types

An interface type is a type for an interface.

An interface type is defined by an interface definition.

  class INTERFACE_TYPE : interface_t {
    
  }

Any Object Type

Any object type object is the type to which any object type can be assigned.

  object

Examples:

  # Examples of any object type
  my $object: object = new Foo;

Basic Types

A basic type is a type whose type dimension is 0 and that can be an element of an array.

The List of Basic Types:

• Numeric types

• Multi-numeric types

• Class types

• Interface types

• The any object type

• The string type

undef Type

The undef type is the type of an undefined value.

void Type

The void type is the type that represents a method defined by a method definition does not return a return value.

  void

Array Types

An array type is a type for an array. An array type consists of a basic type and a type dimension such as [], [][].

  BASIC_TYPE[]..

([].. means one more [])

Examples:

  # Numeric array
  int[]
  double[]
  
  # String array
  string []
  
  # Class array
  Point[]
  
  # Any object array
  object[]
  
  # 2 dimensional array
  int[][]
  
  # 3 dimensional array
  int[][][]

An array type is an object type.

Compilation Errors:

The dimesion is less than or equal to 255. Otherwise, a compilation error occurs.

Numeric Array Types

A numeric array type is an array type of a numeric type.

The List of Numeric Array Types:

  byte[]
  short[]
  int[]
  long[]
  float[]
  double[]

Object Array Types

An object array type is an array type of an object type.

Examples:

  Point[]
  Point[][]
  Stringable[]
  string[]
  object[]

String Array Type

The string array type is the array type the string type.

  string[]

Class Array Types

A class array type is an array type of a class type.

Examples:

  Int[]
  Point[]

Interface Array Types

An interface array type is an array type of an interface type.

Examples:

  Stringable[]
  Cloneable[]

Multi-Dimensional Array Types

A multi-dimensional array type is an array type of an array type.

Examples:

  int[][]
  Int[][]
  string[][][]
  object[][]

A multi-dimensional array is created by the syntax of creating a multi-dimensional array of the new operator.

Multi-Numeric Array Types

A multi-numeric array type is an array type of a multi-numeric type.

Examples:

  Complex_2d[]
  Complex_2f[]

Any Object Array Type

The any object array type object[] is the array type to which any object array type can be assigned.

  object[]

Multi-Numeric Types

A multi-numeric type is a type for a multi-numeric number.

A multi-numeric type is defined by a multi-numeric type definition.

  class MULNUM_TYPE : mulnum_t {
    
  }

Reference Types

A reference type is a type for a reference.

  TYPE*

A reference type consists of a type followed by *.

TYPE must be a numeric type or a multi-numeric type.

Numeric Reference Types

A numeric reference type is a reference type of a numeric type.

The List of Numeric Reference Types:

  byte*
  short*
  int*
  long*
  float*
  double*

Multi-Numeric Reference Types

A multi-numeric reference types is a reference type of a multi-numeric type.

  MULNUM_TYPE*

Examples:

  Complex_2d*
  Complex_2f*

Type Qualifiers

A type qualifier qualify a type.

  QUALIFIER TYPE

The QUALIFIER qualified the type TYPE.

mutable Type Qualifier

The mutable type qualifier qualifies the string type.

  mutable string;

The string of the string type with the mutable type qualifier is able to be set a character.

  my $string = (mutable string)copy "abc";
  $string->[0] = 'd';

Type Initial Value

The value of a type is initialized by its type initial value.

The List of Type Initial Values:

Types	Type Initial Values
byte	0
short	0
int	0
long	0
float	0 (All bits are 0)
double	0 (All bits are 0)
Object Types	undef
Multi-Numeric Types	All fields are set to 0 (All bits are 0)

Type Width

The type width is the length of the runtime stack of the type.

If the type is a multi-numeric type, the type width is the length of the fields, owhterwise it is 1.

Assignment Requirement

The assignment requirement is the requirement whether one type is able to be assigned to another type.

What does it mean to assign one type to another type?

Typically, it is sufficient to consider a case where a value of a type TYPE_FROM is assigned to a variable of a type TYPE_TO.

  my $value : TYPE_FROM;
  my $var : TYPE_TO = $value;

Abstracting this, type-to-type assignment is defined.

  TYPE_TO = TYPE_FROM

Note that this is a concept, not an actual syntax.

Some assinments perform a data conversion.

In the following description, the word "Type" is omitted when it is obvious.

Assignment Requirement to Numeric

Assignment Requirement from Numeric to Numeric

To Larger:

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	byte	byte	No
Yes	short	short	No
Yes	int	int	No
Yes	long	long	No
Yes	float	float	No
Yes	double	double	No
Yes	short	byte	Numeric Widening Conversion
Yes	int	byte	Numeric Widening Conversion
Yes	long	byte	Numeric Widening Conversion
Yes	float	byte	Numeric Widening Conversion
Yes	double	byte	Numeric Widening Conversion
Yes	int	short	Numeric Widening Conversion
Yes	long	short	Numeric Widening Conversion
Yes	float	short	Numeric Widening Conversion
Yes	double	short	Numeric Widening Conversion
Yes	long	int	Numeric Widening Conversion
Yes	float	int	Numeric Widening Conversion
Yes	double	int	Numeric Widening Conversion
Yes	float	long	Numeric Widening Conversion
Yes	double	long	Numeric Widening Conversion
Yes	double	float	Numeric Widening Conversion

To Smaller:

Assignment Requirement Satisfaction	To	From	Data Conversion
Conditional Yes	byte	short	Numeric Narrowing Conversion
Conditional Yes	byte	int	Numeric Narrowing Conversion
Conditional Yes	byte	long	Numeric Narrowing Conversion
No	byte	float	No
No	byte	double	No
Conditional Yes	short	int	Numeric Narrowing Conversion
Conditional Yes	short	long	Numeric Narrowing Conversion
No	short	float	No
No	short	double	No
Conditional Yes	int	long	Numeric Narrowing Conversion
No	int	float	No
No	int	double	No
No	long	float	No
No	long	double	No
No	float	double	No

"Conditional Yes" means if the value of TYPE_FROM is represented by an interger literal and between the max and minimal value of the type of TYPE_TO.

Assignment Requirement from NumericObject to Numeric

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	byte	Byte	Unboxing Conversion
Yes	short	Short	Unboxing Conversion
Yes	int	Int	Unboxing Conversion
Yes	long	Long	Unboxing Conversion
Yes	float	Float	Unboxing Conversion
Yes	double	Double	Unboxing Conversion

Assignment Requirement from Any Object to Numeric

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	byte	Any Object object	Unboxing Conversion
Yes	short	Any Object object	Unboxing Conversion
Yes	int	Any Object object	Unboxing Conversion
Yes	long	Any Object object	Unboxing Conversion
Yes	float	Any Object object	Unboxing Conversion
Yes	double	Any Object object	Unboxing Conversion

Assignment Requirement from Other to Numeric

Assignment Requirement Satisfaction	To	From	Data Conversion
No	NumericX	Other	No

NumericX is a numeric type.

Assignment Requirement to Multi-Numeric

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	Multi-NumericX	Multi-NumericX	No
No	Multi-NumericX	Other	No

Multi-NumericX is a multi-numeric type.

Assignment Requirement to Referenece

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	ReferenceX	ReferenceX	No
No	ReferenceX	Other	No

ReferenceX is a reference type.

Assignment Requirement to String

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	string	string	No
Yes	string	mutable string	No
Yes	mutable string	mutable string	No
No	mutable string	string	No
Yes	string	string	No
Yes	string	NumericX	Numeric-to-String Conversion
Yes	string	undef	No
No	string	Other	No

NumericX is a numeric type.

Assignment Requirement to NumericObject

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	NumericObjectX	NumericObjectX	No
Yes	NumericObjectX	NumericX	Boxing Conversion
Yes	NumericObjectX	undef	No
No	NumericObjectX	Other	No

NumericObjectX is a numeric object type.

NumericX is a numeric type.

Assignment Requirement to Class

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	ClassX	ClassX	No
Yes	ClassX	undef	No
Yes	SuperClassX	ClassX	No
No	ClassX	Other	No

ClassX is a class type.

SuperClassX is a super class of ClassX.

Assignment Requirement to Interface

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	InterfaceX	InterfaceX	No
Yes	InterfaceX	InterfaceSatisfiedX	No
Yes	InterfaceX	undef	No
No	InterfaceX	Other	No

InterfaceX is a an interface type.

InterfaceSatisfiedX is a class type or an interface type that satisfied the interface requirement of InterfaceX.

Assignment Requirement to Any Object

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	Any Object object	ObjectX	No
Yes	Any Object object	NumericX	Boxing Conversion
Yes	Any Object object	undef	No
No	Any Object object	Other	No

ObjectX is an object type.

NumericX is a numeric type.

Assignment Requirement to undef

Assignment Requirement Satisfaction	To	From	Data Conversion
No	undef	X	No

X is a type.

Assignment Requirement to void

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	void	void	No
No	void	X	No

X is a type.

Assignment Requirement to Numeric Array

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	NumericX[]	NumericX[]	No
Yes	NumericX[]	undef	No
No	NumericX[]	Other	No

NumericX is a numeric type.

Assignment Requirement to Multi-Numeric Array

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	Multi-NumericX[]	Multi-NumericX[]	No
Yes	Multi-NumericX[]	undef	No
No	Multi-NumericX[]	Other	No

Multi-NumericX is a multi-numeric type.

Assignment Requirement to String Array

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	string[]	string[]	No
Yes	string[]	undef	No
No	string[]	Other	No

Assignment Requirement to Class Array

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	ClassX[]	ClassX[]	No
Yes	SuperClassX[]	ClassX[]	No
Yes	ClassX[]	undef	No
No	ClassX[]	Other	No

ClassX is a class type.

SuperClassX is a super class of ClassX.

Assignment Requirement to Interface Array

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	InterfaceX[]	InterfaceX[]	No
Yes	InterfaceX[]	InterfaceSatisfiedX[]	No
Yes	InterfaceX[]	undef	No
No	InterfaceX[]	Other	No

InterfaceX is a an interface type.

InterfaceSatisfiedX is a class type or an interface type that satisfied the interface requirement of InterfaceX.

Assignment Requirement to Any Object Array

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	Any Object Array object[]	ObjectX[]..	No
Yes	Any Object Array object[]	undef	No
No	Any Object Array object[]	Other	No

ObjectX is an object type.

[].. is one or more [].

Assignment Requirement to Multi-Dimensional Array

Assignment Requirement Satisfaction	To	From	Data Conversion
Yes	X[]..D	X[]..D	No
Yes	X[]..D	undef	No
Yes	SuperClassX[]..D	ClassX[]..D	No
Yes	InterfaceX[]..D	InterfaceSatisfiedX[]..D	No
No	X[]..D	Other	No

X is a type.

[].. is one or more [].

D means its type dimension that is greater than or eausl to 2.

X[]..D is a multi-dimensional array.

ClassX is a class type.

SuperClassX is a super class of ClassX.

InterfaceX is a an interface type.

InterfaceSatisfiedX is a class type or an interface type that satisfied the interface requirement of InterfaceX.

Cast Requirement

The cast requirement is the requirement whether one type is able to be cast to another type.

What does it mean to cast one type to another type?

Typically, it is sufficient to consider a case where a value of a type TYPE_FROM is casted to TYPE_TO.

  my $value : TYPE_FROM;
  (TYPE_TO)$value;

Abstracting this, type-to-type cast is defined.

  (TYPE_TO)TYPE_FROM

Note that this is a concept, not an actual syntax.

Some type casts perform a data conversion.

Some type casts perform a data check.

In the following description, the word "Type" is omitted when it is obvious.

Cast Requirement to Numeric

Cast Requirement from Numeric to Numeric

To Larger:

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	byte	byte	No	No
Yes	short	short	No	No
Yes	int	int	No	No
Yes	long	long	No	No
Yes	float	float	No	No
Yes	double	double	No	No
Yes	short	byte	Numeric Widening Conversion	No
Yes	int	byte	Numeric Widening Conversion	No
Yes	long	byte	Numeric Widening Conversion	No
Yes	float	byte	Numeric Widening Conversion	No
Yes	double	byte	Numeric Widening Conversion	No
Yes	int	short	Numeric Widening Conversion	No
Yes	long	short	Numeric Widening Conversion	No
Yes	float	short	Numeric Widening Conversion	No
Yes	double	short	Numeric Widening Conversion	No
Yes	long	int	Numeric Widening Conversion	No
Yes	float	int	Numeric Widening Conversion	No
Yes	double	int	Numeric Widening Conversion	No
Yes	float	long	Numeric Widening Conversion	No
Yes	double	long	Numeric Widening Conversion	No
Yes	double	float	Numeric Widening Conversion	No

To Smaller:

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	byte	short	Numeric Narrowing Conversion	No
Yes	byte	int	Numeric Narrowing Conversion	No
Yes	byte	long	Numeric Narrowing Conversion	No
Yes	byte	float	Numeric Narrowing Conversion	No
Yes	byte	double	Numeric Narrowing Conversion	No
Yes	short	int	Numeric Narrowing Conversion	No
Yes	short	long	Numeric Narrowing Conversion	No
Yes	short	float	Numeric Narrowing Conversion	No
Yes	short	double	Numeric Narrowing Conversion	No
Yes	int	long	Numeric Narrowing Conversion	No
Yes	int	float	Numeric Narrowing Conversion	No
Yes	int	double	Numeric Narrowing Conversion	No
Yes	long	float	Numeric Narrowing Conversion	No
Yes	long	double	Numeric Narrowing Conversion	No
Yes	float	double	Numeric Narrowing Conversion	No

Cast Requirement from NumericObject to Numeric

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	byte	Byte	Unboxing Conversion	No
Yes	short	Short	Unboxing Conversion	No
Yes	int	Int	Unboxing Conversion	No
Yes	long	Long	Unboxing Conversion	No
Yes	float	Float	Unboxing Conversion	No
Yes	double	Double	Unboxing Conversion	No

Cast Requirement from Any Object to Numeric

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	NumericX	Any Object object	Unboxing Conversion	No

NumericX is a numeric type.

Cast Requirement from Other to Numeric

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
No	NumericX	Other	No	No

NumericX is a numeric type.

Cast Requirement to Multi-Numeric

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	Multi-NumericX	Multi-NumericX	No	No
No	Multi-NumericX	Other	No	No

Multi-NumericX is a multi-numeric type.

Cast Requirement to Referenece

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	ReferenceX	ReferenceX	No	No
No	ReferenceX	Other	No	No

ReferenceX is a reference type.

Cast Requirement to String

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	string	string	No	No
Yes	string	mutable string	No	No
Yes	mutable string	mutable string	No	No
Yes	mutable string	string	No	is_read_only Operator
Yes	string	string	No	No
Yes	string	NumericX	Numeric-to-String Conversion	No
Yes	string	Any Object object	No	isa Operator
Yes	string	undef	No	No
No	string	Other	No	No

NumericX is a numeric type.

Cast Requirement to NumericObject

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	NumericObjectX	NumericObjectX	No	No
Yes	NumericObjectX	NumericX	Boxing Conversion	No
Yes	NumericObjectX	Any Object object	No	isa Operator
Yes	NumericObjectX	undef	No	No
No	NumericObjectX	Other	No	No

NumericObjectX is a numeric object type.

NumericX is a numeric type.

Cast Requirement to Class

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	ClassX	ClassX	No	No
Yes	SuperClassX	ClassX	No	No
Yes	ClassX	SuperClassX	No	isa Operator
Yes	ClassX	InterfaceX	No	isa Operator
Yes	ClassX	Any Object object	No	isa Operator
Yes	ClassX	undef	No	No
No	ClassX	Other	No	No

ClassX is a class type.

SuperClassX is a super class of ClassX.

InterfaceX is a an interface type.

Cast Requirement to Interface

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	InterfaceX	InterfaceX	No	No
Yes	InterfaceX	InterfaceSatisfiedX	No	No
Yes	InterfaceX	InterfaceY	No	isa Operator
Yes	InterfaceX	Any Object object	No	isa Operator
Yes	InterfaceX	undef	No	No
No	InterfaceX	Other	No	No

ClassX is a class type.

SuperClassX is a super class of ClassX.

InterfaceX is a an interface type.

InterfaceY is a an interface type.

InterfaceSatisfiedX is a class type or an interface type that satisfied the interface requirement of InterfaceX.

Cast Requirement to Any Object

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	Any Object object	ObjectX	No	No
Yes	Any Object object	NumericX	Boxing Conversion	No
Yes	Any Object object	undef	No	No
No	Any Object object	Other	No	No

ObjectX is an object type.

NumericX is a numeric type.

Cast Requirement to Numeric Array

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	byte[]	string	String-to-byte[] Conversion	No
Yes	NumericX[]	NumericX[]	No	No
Yes	NumericX[]	Any Object object	No	isa Operator
Yes	NumericX[]	undef	No	No
No	NumericX[]	Other	No	No

NumericX is a numeric type.

Cast Requirement to Multi-Numeric Array

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	Multi-NumericX[]	Multi-NumericX[]	No	No
Yes	Multi-NumericX[]	Any Object object	No	isa Operator
Yes	Multi-NumericX[]	undef	No	No
No	Multi-NumericX[]	Other	No	No

Multi-NumericX is a multi-numeric type.

Cast Requirement to String Array

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	string[]	string[]	No	No
Yes	string[]	Any Object object	No	isa Operator
Yes	string[]	Any Object Array object[]	No	isa Operator
Yes	string[]	undef	No	No
No	string[]	Other	No	No

Cast Requirement to Class Array

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	ClassX[]	ClassX[]	No	No
Yes	SuperClassX[]	ClassX[]	No	No
Yes	ClassX[]	SuperClassX[]	No	isa Operator
Yes	ClassX[]	Any Object object	No	isa Operator
Yes	ClassX[]	Any Object Array object[]	No	isa Operator
Yes	ClassX[]	undef	No	No
No	ClassX[]	Other	No	No

ClassX is a class type.

SuperClassX is a super class of ClassX.

Cast Requirement to Interface Array

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	InterfaceX[]	InterfaceX[]	No	No
Yes	InterfaceX[]	InterfaceSatisfiedX[]	No	No
Yes	InterfaceX[]	InterfaceY[]	No	isa Operator
Yes	InterfaceX[]	Any Object object	No	isa Operator
Yes	InterfaceX[]	Any Object Array object[]	No	isa Operator
Yes	InterfaceX[]	undef	No	No
No	InterfaceX[]	Other	No	No

ClassX is a class type.

SuperClassX is a super class of ClassX.

InterfaceX is a an interface type.

InterfaceY is a an interface type.

InterfaceSatisfiedX is a class type or an interface type that satisfied the interface requirement of InterfaceX.

Cast Requirement to Any Object Array

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	Any Object Array object[]	ObjectX[]..	No	No
Yes	Any Object Array object[]	undef	No	No
Yes	Any Object Array object[]	Any Object object	No	isa Operator
No	Any Object Array object[]	Other	No	No

ObjectX is an object type.

[].. is one or more [].

Cast Requirement to Multi-Dimensional Array

Cast Requirement Satisfaction	To	From	Data Conversion	Data Check
Yes	X[]..D	X[]..D	No	No
Yes	X[]..D	Any Object object	No	isa Operator
Yes	X[]..D	Any Object Array object[]	No	isa Operator
Yes	X[]..D	undef	No	No
Yes	SuperClassX[]..	ClassX[]..D	No	No
Yes	ClassX[]..	SuperClassX[]..D	No	isa Operator
Yes	InterfaceX[]..D	InterfaceSatisfiedX[]..D	No	No
No	Any Object Array object[]	Other	No	No

X is a type.

[].. is one or more [].

D means its type dimension that is greater than or eausl to 2.

X[]..D is a multi-dimensional array.

ClassX is a class type.

SuperClassX is a super class of ClassX.

InterfaceX is a an interface type.

InterfaceSatisfiedX is a class type or an interface type that satisfied the interface requirement of InterfaceX.

Interface Requirement

The interface requirement is the requirement whether an object type is able to be assigned to an interface type.

  INTERFACE_TYPE_TO = OBJECT_TYPE_FROM

This is the same concept as type-to-type assignment explained in Assignment Requirement.

INTERFACE_TYPE_TO must be an interface type.

OBJECT_TYPE_FROM must be a class type or an interface type.

The following check is performed on every instance method of OBJECT_TYPE_FROM.

If an instance method of INTERFACE_TYPE_TO has the required method attribute, OBJECT_TYPE_FROM or one of its super classes must have a method with the same name.

If OBJECT_TYPE_FROM or one of its super classes has an instance method(this is named METHOD_FROM) with the same name as an instance method of INTERFACE_TYPE_TO, METHOD_FROM must be an instance method and satisfy the interface method requirement.

Interface Method Requirement

The interface method requirement is the requirement whether a method is able to be assigned to an interface method.

  INTERFACE_METHOD_TO = METHOD_FROM

This is a concept that converts the type-to-type assignment explained in Assignment Requirement to method-to-method assignment.

INTERFACE_METHOD_TO must be an instance method.

METHOD_FROM must be an instance method.

The length of the arguments of the method of the INTERFACE_METHOD_TO type must be greater than or equal to the length of the required arguments the method of the INSTANT_METHOD_TYPE_FROM type.

The every argument other than at 0 index of the method of the INSTANT_METHOD_TYPE_FROM must satisfy the assignment requirement to the argument as the same index of the method of the INTERFACE_METHOD_TO without a data conversion and with interface exactly matched.

The return type of the method of the INSTANT_METHOD_TYPE_FROM must must satisfy the assignment requirement to the return type of the method of the INTERFACE_METHOD_TO without a data conversion and with interface exactly matched.

See Also

• SPVM::Document::Language::Class

• SPVM::Document::Language::Operators

• SPVM::Document::Language::Statements

• SPVM::Document::Language

• SPVM::Document

Copyright & License

Copyright (c) 2023 Yuki Kimoto

MIT License

cpanm SPVM

perl -MCPAN -e shell
install SPVM