src/main/java/org/cosette/Environment.java
/**
     * Record the level for a correlation variable and increment the global level in a new Environment instance based on
     * the current Environment instance. This will not change the current environment.
     *
     * @param id    The correlation variable. If this is null, nothing will be recorded.
     * @param delta The change in global level.
     * @return A new Environment instance after the change.
     */
Record the level for a correlation variable and increment the global level in a new Environment instance based on
the current Environment instance. This will not change the current environment.

@param id    The correlation variable. If this is null, nothing will be recorded.
@param delta The change in global level.
@return A new Environment instance after the change.
Record the level for a correlation variable and increment the global level in a new Environment instance based on the current Environment instance . This will not change the current environment . @param id The correlation variable . If this is null nothing will be recorded . @param delta The change in global level . @return A new Environment instance after the change .
public Environment amend(CorrelationId id, int delta) {
        HashMap<CorrelationId, Integer> copy = new HashMap<>(environment);
        if (id != null) {
            copy.put(id, level);
        }
        return new Environment(relMapper, relOptTables, copy, level + delta);
    }
public Environment amend ( CorrelationId id , int delta ) { HashMap < CorrelationId , Integer > copy = new HashMap < > ( environment ) ; if ( id != null ) { copy . put ( id , level ) ; } return new Environment ( relMapper , relOptTables , copy , level + delta ) ; }
Record the level for a correlation variable and increment the global level in a new Environment instance based on
 the current Environment instance.
Record the level for a correlation variable and increment the global level in a new Environment instance based on the current Environment instance .