set_domain

Gamma: Version 4.0
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# `set_domain`

`set_domain` -- sets the default domain for future calls.

## Syntax

    set_domain (domain_name)

## Arguments

`domain_name`

  A string.

## Returns

The `domain_name` argument.

## Description

This function sets the default Cascade DataHub domain for all future calls to `read_point`, `read_existing_point`, `register_point`, `register_existing_point`, `write_point` and `write_existing_point`. The default domain can be overridden by explicitly placing the domain name at the beginning of the point name, separated by a colon (:). For example, a variable named `tank_level` in the default domain would have to be named `acme:tank_level` in the "acme" domain.

| There is a possibility of aliasing points. If the default domain is "acme" then the point `tank_level` and the point `acme:tank_level` refer to the same datahub point. If both of these names are used in a Gamma program then one of them will not behave correctly. It is the responsibility of the programmer to ensure that there is no aliasing in the assigned names, either by always explicitly naming a point's domain or by programming carefully.

## Example

        Gamma> set_domain("acme");
        t
        Gamma> read_point(#tank_level);
        12.5
        Gamma> set_domain("steamplant");
        t
        Gamma> read_point("tank_level");
        4.35
        Gamma> read_point("acme:tank_level");
        12.5

## See Also

`read_point`, `read_existing_point`, `register_point`, `write_point`, `write_existing_point`

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