REDUCE

dynamic-clause array-clause

[GIVING operand5]

This document covers the following topics:

• Function

• Syntax Description

For an explanation of the symbols used in the syntax diagram, see Syntax Symbols.

Related statements: EXPAND | RESIZE

Belongs to Function Group: Memory Management Control for Dynamic Variables or X-Arrays.

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Function

The REDUCE statement is used to reduce:

• the allocated length of a dynamic variable (dynamic-clause), or

• the number of occurrences of X-arrays (array-clause).

For further information, see also the following sections in the Programming Guide:

• Using Dynamic Variables

• Allocating/Freeing Memory Space for a Dynamic Variable

• X-Arrays

• Storage Management of X-Group Arrays

Syntax Description

Operand Definition Table:

Operand	Possible Structure					Possible Formats													Referencing Permitted	Dynamic Definition
operand1		S	A			A	U					B							no	no
operand2	C	S								I									no	no
operand3			A	G		A		N	P	I	F	B	D	T	L	C	G	O	yes	no
operand4	C	S					U	N	P	I									no	no
operand5		S								I4									no	yes

Syntax Element Description:

Syntax Element	Description
dynamic-clause	Dynamic Clause: The REDUCE DYNAMIC VARIABLE statement reduces the allocated length of a dynamic variable (operand1) to the length specified (operand2). For further information, see Dynamic Clause below.
operand1	Dynamic Variable: operand1 is the dynamic variable for which the length is to be reduced.
operand2	Target Length of Dynamic Variable: operand2 is used to specify the length to which the dynamic variable is to be reduced. The value specified must be a non-negative integer constant or a variable of type Integer 4 (I4).
array-clause	Array Clause: The REDUCE ARRAY statement reduces the number of occurrences of the X-array (operand3) to the upper and lower bound specified with (dim[,dim[,dim]]). For further information, see Array Clause below.
operand3	X-Array: operand3 is the X-array. The occurrences of the X-array can be reduced. The index notation of the array is optional. As index notation only the complete range notation * is allowed for each dimension.
dim operand4	Dimension: The lower and upper bound notation (operand4 or asterisk) to which the X-array should be reduced is specified here. If the current value of the upper or lower bound should be used, an asterisk (*) must be specified instead of operand4. For further information, see Dimension below.
GIVING operand5	GIVING Clause: If the GIVING clause is not specified, Natural runtime error processing is triggered if an error occurs. If the GIVING clause is specified, operand5 contains the Natural message number if an error occurred, or zero upon success.

Dynamic Clause

[SIZE OF] DYNAMIC [VARIABLE] operand 1 TO operand2

The REDUCE DYNAMIC VARIABLE statement reduces the allocated length of a dynamic variable (operand1) to the length specified (operand2). The allocated memory of the dynamic variable which is beyond the given length is released immediately, i.e., when the statement is executed.

If the currently allocated length (*LENGTH) of the dynamic variable is greater than the given length, *LENGTH is set to the given length and the content of the variable is truncated (but not modified). If the given length is larger than the currently allocated length of the dynamic variable, the statement will be ignored.

Array Clause

[OCCURRENCES OF] ARRAY operand3 TO

0 (dim[,dim[,dim]])

If REDUCE TO 0 (zero) is specified, all occurrences of the X-array are released. In other words, the whole array is reduced.

The REDUCE ARRAY statement reduces the number of occurrences of the X-array (operand3) to the upper and lower bound specified with TO (dim[,dim[,dim]]).

An upper or lower bound used in a REDUCE statement must be exactly the same as the corresponding upper or lower bound defined for the array.

Example:

DEFINE DATA LOCAL
1 #a(I4/1:*)
1 #g(1:*)
  2 #ga(I4/1:*)

1 #i(i4)
END-DEFINE
...


*/ reducing #a (1:10)

REDUCE ARRAY #a TO (1:10)       /* #a is reduced 
REDUCE ARRAY #a TO (*:10)       /* to 10 occurrences.


*/ reducing #ga (1:10,1:20)

REDUCE ARRAY #g TO (1:10)       /* 1st dimension is set to (1:10)
REDUCE ARRAY #ga TO (*:*,1:20)  /* 1st dimension is dependent and 
                                /* therefore kept with (*:*)
                                /* 2nd dimension is set to (1:20)
 
REDUCE ARRAY #a TO (5:10)       /* This is rejected because the lower index
                                /* must be 1 or *
REDUCE ARRAY #a TO (#i:10)      /* This is rejected because the lower index
                                /* must be 1 or *

REDUCE ARRAY #ga TO (1:10,1:20) /* (1:10) for the 1st dimension is rejected
                                /* because the dimension is dependent and 
                                /* must be specified with (*:*).

For further information, see

• Storage Management of X-Arrays

• Storage Management of X-Group Arrays

Dimension

Each of the dimensions (dim) specified in the Array Clause is defined using the following syntax:

	*
		*		:		*
		operand4				operand4

The lower and upper bound notation (operand4 or asterisk) to which the X-array should be reduced is specified here. If the current value of the upper or lower bound should be used, an asterisk (*) may be specified in place of operand4. In place of *:*, you may also specify a single asterisk.

The number of dimensions (dim) must exactly match the defined number of dimensions of the X-array (1, 2 or 3).

When using the REDUCE statement, it is only possible to decrease the number of occurrences. If the requested number is larger than the currently allocated number of occurrences, it will simply be ignored.