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6.Structure Functions

These functions are defined in `structfuns.sl`.

6.1struct_filter

Synopsis

Apply a filter to a struct

Usage

`struct_filter(Struct_Type s, Int_Type i)`

Description

This function applies the filter `i` to the fields of a structure by performing the operation

``` s.field = s.field[i]; ```
on each array field of the structure. Scalar fields will not be modified.

The `dim` qualifier may be used to filter on a specific array dimension. For example, consider the structure

``` s = struct { a = Int_Type[10], b = Int_Type[10,20] }; ```
Then
``` struct_filter (s, i; dim=0); ```
would produce the same result as
``` s.a = s.a[i]; s.b = s.b[i,*]; ```

Notes

By default this function modifies the fields of the structure passed to it. Sometimes it is desirable to create a new structure and leave the old one untouched. This may be achieved using the `copy` qualifier, e.g.,

``` filtered_s = struct_filter (s, i; copy); ```

`where`

6.2struct_combine

Synopsis

Combine two or more structures

Usage

`new_s = struct_combine (s1, s2, ...)`

Description

This function creates a new structure from two or more structures `s1`, `s2`,.... The new structure will have fields formed by the union of the fields of the input structures. The new structure fields will be given values that correspond to the fields of the input structures. If more than one structure has the same field name, the value of the field will be given by the last structure.

If any of the input values is a string, or an array of strings, then it will be interpreted as a representing a structure with the corresponding field names. This is a useful feature when one wants to expand a structure with new field names, e.g.,

``` s = struct { foo, bar }; t = struct_combine (s, "baz"); % t = struct {foo, bar, baz}; ```

Notes

The same effect can be achieved by using the dereference operator, e.g.,

``` t = struct { @s, "baz" }; ```

`get_struct_field_names`

6.3struct_field_exists

Synopsis

Determine whether or not a structure contains a specified field

Usage

`Int_Type struct_field_exists (Struct_Type s, String_Type f)`

Description

This function may be used to determine if a structure contains a field with a specfied name. It returns 0 if the structure does not contain the field, or non-zero if it does.

`get_struct_field_names`