Unexpected handling of duplicate column names

[4er4er4er]

The attached example aborts with:

Error at _cmdno 152 executing "read_table" command
(file modex-hor.run, line 426, offset 11600):

	Error reading table TICenTer with table handler amplxl:
	Could not parse data

This is the table that amplxl is trying to read:

table TICenTer IN 'amplxl' (pinpxls) 'backup=false':
    sthegen <- [Unidad],
    pthetyp ~ TipoCen,
    pthebar ~ Barra,
    pthelaw ~ LeyERNC,
    pthemngro ~ PotMin,
    pthemxgro ~ PotMax,
    pthestup ~ CosPart,
    pthestdn ~ CosDete,
    ptheico ~ ConsInt,
    pthefor ~ TSFor,
    pthehea ~ ConsEsp,
    pthenfc ~ CVNC,
    pthemrk ~ Marcador,
    pthefac ~ Factor,
    pthemksm ~ SumMul;

The underlying error is that two columns of table TICenTer are labeled Unidad:

• The 1st column, which provides a list of unique thermal generating units that are supposed to populate the set sthegen.
• The 14th column, which specifies units of measurement.

What happens here is consistent with amplxl trying to populate sthegen from the 14th column, and -- since the entries in that column are not unique -- giving the mysterious Could not parse data error as reported in issue #12.

To use the example, put the mod and run files in the same directory as the AMPL executable, and put the two xlsx files in a subdirectory named test. As expected, the problem goes away when the 14th column is labeled something else, like Unidades.