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SAP NEWS-71-DECFLOAT documentation, setup help and example usage
Decimal Floating Point Numbers in Release 7.0, EhP2
Decimal floating point numbers with the types decfloat16 and decfloat34 have been introduced in ABAP to satisfy the demand for more precise processing of decimal numbers with a large range of values. The existing ABAP type p (packed number) represents a decimal number precisely and can be calculated precisely (apart from unavoidable commercial rounding), but the value range is often too small. The existing ABAP type f (binary floating point number) has a large value range, but cannot represent every decimal number precisely due to the internal binary representation.
Both of these requirements are satisified by decimal floating point numbers. Unlike binary floating point numbers, decimal floating point numbers are represented internally with a decimal mantissa. Each decimal number can be represented precisely within the length of the mantissa (16 or 34) and it can be used for calculations in the same way as with type p . Unlike type p , the number of decimal places is not a property of the data type; an exponent of the value determines the decimal places instead. This means that decimal floating point numbers have the advantage of providing a very large range of values.
1 New predefined ABAP types decfloat16 and decfloat34
2 New predefined types in ABAP Dictionary
3 New predefined functions round and rescale
4 Lossless calculations
5 Methods for decimal floating point numbers
6 Formatting of decimal floating point numbers using WRITE
ABAP_MODIFICATION_1 New predefined ABAP types decfloat16 and decfloat34
From Release 7.0, EhP2 , ABAP includes the new predefined numeric ABAP types decfloat16 and decfloat34 for decimal floating point numbers . The corresponding data objects are eight bytes or 16 bytes long and the data objects are aligned in their lengths. The value range is determined by mantissas of the length -383 and +384 or. -6143 and +6144. The new generic ABAP type decfloat covers both new types, decfloat16 and decfloat34 .
The following changes have been caused by the new types:
New conversion and comparison rules have been introduced for the new types.
If a decimal floating point number appears in an arithmetic expression , the calculation type is decfloat34 .
The floating point functions
exp , log , log10 , and sqrt now no longer work just with arguments of type f ; they now also work with arguments of type decfloat16 and decfloat34 . The type of the argument determines the type of the return code. Decimal floating point numbers cannot be used as arguments for the remaining floating point functions at the moment.
ABAP_MODIFICATION_2 New predefined types in ABAP Dictionary
The following new types have been introduced in ABAP Dictionary for the new ABAP types decfloat16 and decfloat34 :
DF16_DEC and DF34_DEC are used by database fields in which decimal floating point numbers, such as packed numbers with type DEC are stored. Database writes can cause roundings and overflows.
DF16_RAW and DF34_RAW are used by database fields in which decimal floating point numbers are stored in their internal representation.
DF16_SCL and DF34_SCL are used by database fields in which decimal floating point numbers are stored with their scaling. In this kind of field, the decimal floating point numbers are stored as in DF16_RAW or DF34_RAW . The scaling must be specified in a direct successor database field with type INT2 . When a decimal floating point number is written, this field is automatically filled with the scaling and during reading, the scaling is automatically taken from it.
Data elements with these types can be used to declare fields in database tables and in dynpros. An output style can be specified in a domain or directly in a structure component created with one of these types. For dynpro fields whose data type is not defined in ABAP Dictionary, the output style can be defined in Screen Painter .
ABAP_MODIFICATION_3 New predefined functions round and rescale
The new rounding functions
round and rescale enable decimal floating point numbers to be rounded or their scaling to be changed. New constants have been added to the class
CL_ABAP_MATH . These constants can be used to specify the rounding rule.
ABAP_MODIFICATION_4 Lossless Calculations
The new addition EXACT of the statement
COMPUTE can be used to force a lossless calculation for decimal floating point numbers, under certain prerequisites. No roundings are allowed in a lossless calculation; they raise the exception
CX_SY_CONVERSION_ROUNDING .
ABAP_MODIFICATION_5 Methods for decimal floating point numbers
Methods for operations with floating point numbers have been added to the class CL_ABAP_MATH .
Method GET_SCALE gets the scaling of a
decimal floating point number .
Method GET_NUMBER_OF_DIGITS gets the
precision of a decimal floating point number
.
The method NORMALIZE gets a normalized floating point number. This means that the scaling and precision of an input value are changed so that the mantissa has no trailing zeros.
The method GET_MAX_DB_VALUE gets the maximum value of a number of the type DF16_DEC or DF34_DEC on the database (from EhP1 ).
The method GET_DB_LENGTH_DECS gets the length and number of decimal places of a number of the type DF16_DEC or DF34_DEC
on the database (from EhP1 ).
The new class CL_ABAP_DECFLOAT contains special methods for decimal floating point numbers.
The methods READ_DECFLOAT34 and READ_DECFLOAT16 convert character-like data objects to decimal floating point numbers and, unlike regular assignments, enable enhanced exception handling.
ABAP_MODIFICATION_6
Predefined formats have been defined for the new types decfloat16 and decfloat34 for the statements WRITE ... TO for formatted assignments and WRITE for list outputs. The predefined output lengths for list output are 24 and 46.
The new addition STYLE has been added to the WRITE statements for the formatting of decimal floating point numbers with different formats.
Documentation extract taken from SAP system, � Copyright SAP AG. All rights reserved
