uk.ac.starlink.table.LoopTableScheme Maven / Gradle / Ivy
package uk.ac.starlink.table;
/**
* TableScheme that yields a table with a single column giving loop
* variable values.
*
* @author Mark Taylor
* @since 20 Jul 2020
*/
public class LoopTableScheme implements TableScheme, Documented {
public LoopTableScheme() {
}
public String getSchemeName() {
return "loop";
}
public String getSchemeUsage() {
return "|,[,]";
}
public String getExampleSpecification() {
return "6";
}
public String getXmlDescription() {
String prefix = ":" + getSchemeName() + ":";
return new StringBuffer()
.append( "Generates a table whose single column\n" )
.append( "increments over a given range.\n" )
.append( "
\n" )
.append( "The specification may either be a single value N\n" )
.append( "giving the number of rows,\n" )
.append( "which yields values in the range 0..N-1,\n" )
.append( "or two or three comma-separated values\n" )
.append( "giving the start, end\n" )
.append( "and optionally step\n" )
.append( "corresponding to the conventional specification\n" )
.append( "of a loop variable.\n")
.append( "
\n" )
.append( "The supplied numeric parameters are interpreted as\n" )
.append( "floating point values, but the output column type\n" )
.append( "will be 32- or 64-bit integer\n" )
.append( "or 64-bit floating point,\n" )
.append( "depending on the values that it has to take.\n" )
.append( "
" )
.append( "Examples:\n" )
.append( "
\n" )
.append( "" + prefix + "5:\n" )
.append( "a 5-row table whose integer column has values\n" )
.append( "0, 1, 2, 3, 4\n" )
.append( "" + prefix + "10,20:\n" )
.append( "a 10-row table whose integer column has values\n" )
.append( "10, 11, ... 19\n" )
.append( "" + prefix + "1,2,0.25:\n" )
.append( "a 10-row table whose floating point column has values\n" )
.append( "1.00, 1.25, 1.50, 1.75\n" )
.append( "" + prefix + "1e10:\n" )
.append( "a ten billion row table, with 64-bit integer values\n" )
.append( "
\n" )
.append( "\n" )
.toString();
}
public StarTable createTable( String spec ) throws TableFormatException {
String[] args = spec.split( ",", -1 );
String colName = "i";
double start = 0;
double end = 16;
double step = 1;
Boolean isInteger = null;
int narg = args.length;
if ( narg < 1 || narg > 3 ) {
throw new TableFormatException( "Wrong number of args");
}
try {
if ( narg == 1 ) {
end = Double.parseDouble( args[ 0 ] );
}
else if ( narg >= 2 ) {
start = Double.parseDouble( args[ 0 ] );
end = Double.parseDouble( args[ 1 ] );
}
if ( narg > 2 ) {
step = Double.parseDouble( args[ 2 ] );
}
}
catch ( NumberFormatException e ) {
throw new TableFormatException( "Bad number", e );
}
return new LoopStarTable( colName, start, end, step, isInteger );
}
}