General Integer Variables
By default, LINGO assumes all variables in a model are continuous. In many applications, fractional values may be undesirable. You won’t be able to hire two-thirds of a person, or sell half an automobile. In these instances, you will want to make use of the general integer variable domain function, @GIN.
The syntax of the @GIN function is:
@GIN( variable_name);
where variable_name is the name of the variable you wish to make general integer. The @GIN function may be used in a model anywhere you would normally enter a constraint. The @GIN function can be embedded in an @FOR statement to allow you to easily set all, or selected, variables of an attribute to be general integers. Some examples of @GIN are:
Example 1: @GIN( X);
makes the scalar variable X general integer,
Example 2: @GIN( PRODUCE( 5));
makes the variable PRODUCE( 5) general integer,
Example 3: @FOR( DAYS( I): @GIN( START( I)));
makes all the variables of the START attribute general integer.