public class SyntheticColumn
extends uk.ac.starlink.table.ColumnData
The engine used for expression evaluation is the GNU Java Expressions Library (JEL).
Constructor and Description |
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SyntheticColumn(uk.ac.starlink.table.ValueInfo vinfo,
java.lang.String expression,
java.lang.Class resultType,
uk.ac.starlink.ttools.jel.RandomJELRowReader rowReader)
Constructs a new synthetic column from an algebraic expression
applied to a table.
|
Modifier and Type | Method and Description |
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java.lang.Object |
readValue(long lrow) |
void |
setExpression(java.lang.String expression,
java.lang.Class resultType,
uk.ac.starlink.ttools.jel.RandomJELRowReader rowReader)
Sets the algebraic expression which this column uses to calculate
its results.
|
public SyntheticColumn(uk.ac.starlink.table.ValueInfo vinfo, java.lang.String expression, java.lang.Class resultType, uk.ac.starlink.ttools.jel.RandomJELRowReader rowReader) throws gnu.jel.CompilationException
vinfo
- template for the new columnexpression
- algebraic expression for the value of this
columnresultType
- a Class for the result, presumably one of the
primitive wrapper types or String.class. If null
a suitable class is chosen automatically.rowReader
- context for JEL expression evaluationgnu.jel.CompilationException
public void setExpression(java.lang.String expression, java.lang.Class resultType, uk.ac.starlink.ttools.jel.RandomJELRowReader rowReader) throws gnu.jel.CompilationException
expression
- the string giving the algebraic exprssion for
this column's value in terms of other columnsresultType
- a Class for the result, presumably one of the
primitive wrapper types or String.class. If null
a suitable class is chosen automatically.rowReader
- context for JEL expression evaluationgnu.jel.CompilationException
public java.lang.Object readValue(long lrow) throws java.io.IOException
readValue
in class uk.ac.starlink.table.ColumnData
java.io.IOException
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