Implicit Conversion in Method Overloading in Managed COBOL

An implicit conversion exists from type S to type T if it is possible to assign an object of type S to an object of type T, with the equivalent of the following statement:

SET obj-T TO obj-S

The following types of implicit conversion are available:

Identity conversions

This simply means that S is the same type as T

Implicit numeric conversions

COBOL generally allows any numeric item to be assigned to any other, with any loss of data being the responsibility of the user. However, when determining if a conversion exists for the purposes of method overloading, we distinguish between proper conversions and truncation conversions. Proper conversions are those for which no loss of data magnitude should result, though even in this case precision can be lost when converting between fixed point and floating point.

For managed COBOL types, proper implicit conversions include:

binary-char	binary-short binary-long binary-double float-short float-long decimal
binary-char unsigned	The same as binary-char, plus: binary-short unsigned binary-long unsigned binary-double unsigned
binary-short	binary-long binary-double float-short float-long decimal
binary-short unsigned	The same as binary-short, plus: binary-long unsigned binary-double unsigned
binary-long	binary-double float-short float-long decimal
binary-long unsigned	The same as binary-long, plus: binary-double unsigned
binary-double	float-short float-long decimal
binary-double unsigned	The same as binary-double
character	binary-short unsigned binary-long binary-long unsigned binary-double binary-double unsigned float-short float-long decimal
float-short	float-long

Implicit enumeration conversions

The value 0 may be converted to any enum type

Implicit reference conversions

If S and T are reference types, S may be assigned to T when:

• Type S is derived (directly or indirectly) from type T. This includes the case where T is java.lang.Object since all types derive from that
• Type S implements interface type T
• If S is an array type with element type E1 and T is an array type with element type E2, then S can be assigned to T provided:
  • S and T have the same number of dimensions
  • Both E1 and E2 are reference types
  • An implicit conversion exists from E1 to E2
• Any array type may be assigned to type java.util.Array in JVM COBOL
• Null may be assigned to any reference type

Boxing conversions

Any value type can be converted to a java.lang.Object type by a process known as boxing. As part of this process the value is copied onto the object heap and a reference is created

Implicit constant expression conversions

Any numeric constant can be converted to any type capable of containing the full value of that constant. For instance the value 1 can be converted both to BINARY-CHAR UNSIGNED and to BINARY-CHAR.

User defined implicit conversions

A user defined implicit conversion consists of an optional implicit numeric conversion from S to S1 followed by the execution of a user defined implicit conversion operator resulting in T1, followed by another optional implicit numeric conversion to T. User defined implicit conversion operators are defined in COBOL with OPERATOR-ID IMPLICIT and result in methods with the name op_Implicit.