Get the name of the column at a given index within the Table astColumnName
This function is intended primarily as a means of iterating round all the columns in a Table. For this purpose, the number of columns in the Table is given by the Ncolumn attribute of the Table. This function could then be called in a loop, with the index value going from zero to one less than Ncolumn.
Note, the index associated with a column decreases monotonically with the age of the column: the oldest Column in the Table will have index one, and the Column added most recently to the Table will have the largest index.
" Ncolumn" . The returned pointer is guaranteed to remain valid and the string to which it points will not be over-written for a total of 50 successive invocations of this function. After this, the memory containing the string may be re-used, so a copy of the string should be made if it is needed for longer than this.
A NULL pointer will be returned if this function is invoked with the AST error status set, or if it should fail for any reason.