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Using a style

TaQL can be used from different languages, in particular Python and Glish. Each has its own conventions breaking down into three important categories:

• 0-based or 1-based indexing.
• Fortran-order or C-order of arrays.
• Inclusive or exclusive end in start:end ranges.

The user can set the style (convention) to be used by preceeding a TaQL statement with

USING STYLE value, value, ...

The possible (case-independent) values are:

• BASE0 or BASE1 telling the indexing style.
• ENDEXCL or ENDINCL telling the range style.
• CORDER or FORTRANORDER telling the array style.
• PYTHON which is equivalent to BASE0,ENDEXCL,CORDER
• GLISH which is equivalent to BASE1,ENDINCL,FORTRANORDER

If multiple values are given for a category, the last one will be used. The default style used is GLISH, which is the way TaQL always worked before this feature was introduced.

It is important to note that the interpretation of the axes numbers depends on the style being used. E.g. when using glish style, axes numbers are 1-based and in Fortran order, thus axis 1 is the most rapidly varying axis. When using python style, axis 0 is the most slowly varying axis.
AIPS++ arrays are in Fortran order, but TaQL maps it to the style being used. Thus when using python style, the axes will be reversed (data will not be transposed).

The style feature has to be used with care. A given TaQL statement will behave differently when used with another style.