Conventions for writing VTL Transformations

When more Transformations are written in a text, the following conventions apply.

Transformations:

  • A Transformation can be written in one or more lines, therefore the end of a line does not denote the end of a Transformation.

  • The end of a Transformation is denoted by a semicolon (;).

Comments:

Comments can be inserted within VTL Transformations using the following syntaxes.

  • A multi-line comment is embedded between /* and */ and, obviously, can span over several lines:

/\* multi-line
comment text \*/

  • A single-line comment follows the symbol // up to the next end of line:

// text of a comment on a single line

  • A sequence of spaces, tabs, end-of-line characters or comments is considered as a single space.

  • The characters /* , */ , // and the whitespaces can be part of a string literal (within double quotes) but in such a case they are part of the string characters and do not have any special meaning.

Examples of valid comments:

Example 1:

\* this is a multi-line
Comment */

Example 2:

// this is single-line comment

Example 3:

DS_r <- /* A is a dataset */ A + /* B is a dataset */ B ;

(for the VTL this statement is the Transformation DS_r <- A + B ; )

Example 4:

DS_r := DS_1 // my comment
        * DS_2 ;

(for the VTL this statement is the Transformation DS_r := DS_1 * DS_2 ; )