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COMPUTE

Short Reference

Other versions: 7.31 | 7.40 | 7.54

Syntax


 [COMPUTE] [EXACT] result = arith_exp |
string_exp | bit_exp.

Addition

... EXACT

Effect

This statement assigns the result of a calculation expression to the variable result. The keyword COMPUTE can be omitted. A calculation expression is:

The data type of result must be either a numeric data object, a character-like data object, or a byte-like data object. If required, the result of the expression is converted to the data type of result.

The following variants exist in addition to the main variant above:

  • [COMPUTE] result = dobj.
  • [COMPUTE] result ?= dobj.

    If, instead of a calculation expression on the right, a single data object has been specified without a prefixed sign or bit operator BIT-NOT this is not a complete arithmetic expression or bit expression. The calculation with a subsequent assignment becomes a simple assignment. These two variants then function just like MOVE dobj {TO|?TO} result. There is then no shared calculation type into which the operands are converted before the assignment; instead, the source field is converted into the data type of the target field, if required. EXACT, however, always functions like a calculation.
  • [COMPUTE] destination1 = destination2 = ... = result = arith_exp|string_exp|bit_exp|dobj.

    In this variant, the variable result is assigned a value in accordance with the rules of the statement COMPUTE; destination1, destination2, ... are given values in accordance with multiple assignment rules.

Programming Guideline

Omit the COMPUTE keyword


Notes

  • Without the EXACT addition, the right side of the statement COMPUTE is a general expression position.
  • In addition to numeric calculations with an arithmetic expression, this means that the statement COMPUTE also permits character string and bit operations with a string expression or a bit expression, which is why they are grouped together under calculation expression.
  • If, on the right side, only a predefined function with a single data object is specified, the COMPUTE statement without the EXACT addition behaves like the MOVE statement. If the argument in the function is a calculation expression, the entire right-hand side is a calculation expression.


Example

The first assignment is the same as a COMPUTE statement and the value returned in result is "731036", or the number of days since 01.01.0001. The second assignment, however, is the same as a MOVE statement and the value returned in result is "20020704".

DATA: result TYPE string, 
      date   TYPE d VALUE '20020704'. 

result = + date. 
result =   date.

Addition

... EXACT

Effect

The EXACT addition, which cannot currently be specified without COMPUTE, checks whether a lossless calculation (in which no rounding is permitted) takes place. A simplified arithmetic expression can be specified on the right side. The calculation type is always decfloat34. If rounding is required by the statement, the exception CX_SY_CONVERSION_ROUNDING is raised. Rounding can take place when operands are converted to the calculation type, during the calculation, or when the result is converted to the target field.

The exception is raised when the first subexpression that requires a rounding is calculated. The target variable result remains unchanged when the exception is raised. When the exception is handled, the VALUE attribute in the exception object contains the result that a calculation returns without the EXACT addition. The attribute OPERATION contains the first operation that had to be rounded; conversions are represented by ":=".

The following restrictions apply to the simplified arithmetic expression on the right, as opposed to general arithmetic expressions:

  • The permitted arithmetic operators are +, -, *, and /. The operators DIV, MOD, and ** cannot be used.
  • The permitted predefined functions are abs, sign, ceil, floor, trunc, frac, round, and rescale. These functions do not raise the exception CX_SY_CONVERSION_ROUNDING. No other predefined functions can be specified because their results are not lossless (in principle).
  • No operands of data type x and xstring can be specified.
  • No functional methods can be specified, since the losslessness requirements cannot be applied to the method execution.
  • Operands of the type f (binary floating point numbers) are not permitted because they cannot represent every decimal number precisely, due to their internal representation.

The target variable result can have any elementary data type except f.


Note

The first calculation in lossless calculations that requires rounding raises an exception. This means that arithmetic expressions that are mathematically identical but constructed in different ways can display different behavior (see example).


Example

See Lossless Calculations


Example

Refer to Decimal Floating Point Numbers, Arithmetic Calculations.

Exceptions


Catchable Exceptions

CX_SY_CONVERSION_ROUNDING

  • Cause: Rounding in a lossless calculation
    Runtime Error: UNCAUGHT_EXCEPTION

Continue

Lossless Calculations

Floating Point Numbers, Arithmetic Calculations