REDUCE

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# REDUCE

`REDUCE` |  | dynamic-clause array-clause |  | [`GIVING` operand5]

This document covers the following topics:

- REDUCE Usage

- REDUCE 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.

## REDUCE Usage

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

## REDUCE 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 | U | N | P | I | F | B | D | T | L | C | G | O | yes | no
`operand4` | C | S |  |  |  |  |  | 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`] operand1 `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.

### On this page

- REDUCE Usage
- REDUCE Syntax Description