uk.ac.starlink.table.LoopStarTable Maven / Gradle / Ivy
package uk.ac.starlink.table;
import java.util.function.DoubleFunction;
/**
* Single-column table whose column values are the values of a loop iterator
* variable.
*
* @author Mark Taylor
* @since 6 Nov 2013
*/
public class LoopStarTable extends ColumnStarTable {
private final long nrow_;
/**
* Constructs a loop table from values like the initialisers of a for loop.
* The isInteger parameter may be set True for an
* integer column, False for a Double column, and null if the type is
* to be determined from the input values (integer if all are integers).
* Integer columns are 32-bit if the values permit, otherwise 64-bit.
*
* @param colName name of the single column name in the table
* @param start initial (row 0) value of variable
* @param end value which variable will not exceed
* @param step per-row increment of variable
*/
public LoopStarTable( final String colName, final double start,
final double end, final double step,
Boolean isInteger ) {
final boolean isInt =
isInteger == null
? start == (long) start && end == (long) end
&& step == (long) step
: isInteger.booleanValue();
String descrip = "Loop variable";
final ColumnData colData;
final long nrow;
final DoubleFunction typedValue;
final Class clazz;
if ( isInt ) {
nrow = ( (long) end - (long) start ) / (long) step;
boolean is32bit =
start == (int) start && end == (int) end && step == (int) step;
if ( is32bit ) {
clazz = Integer.class;
typedValue = dval -> new Integer( (int) dval );
}
else {
clazz = Long.class;
typedValue = dval -> new Long( (long) dval );
}
}
else {
nrow = (long) Math.floor( ( end - start ) / step );
clazz = Double.class;
typedValue = dval -> new Double( dval );
}
nrow_ = Math.max( 0, nrow );
addColumn( new ColumnData( new ColumnInfo( colName, clazz, descrip ) ) {
public Object readValue( long irow ) {
return typedValue.apply( start + irow * step );
}
} );
}
public long getRowCount() {
return nrow_;
}
}