4.3.1.1 Program transformation with source layout info

This sections documents extended versions of the program transformation predicates that also transform the source layout information. Extended layout information is currently processed, but unused. Future versions will use for the following enhancements:

• More precise locations of warnings and errors
• More reliable setting of breakpoints
• More reliable source layout information in the graphical debugger.

expand_goal(+Goal1, ?Layout1, -Goal2, -Layout2)

goal_expansion(+Goal1, ?Layout1, -Goal2, -Layout2)

expand_term(+Term1, ?Layout1, -Term2, -Layout2)

term_expansion(+Term1, ?Layout1, -Term2, -Layout2)

dcg_translate_rule(+In, ?LayoutIn, -Out, -LayoutOut)

These versions are called before their 2-argument counterparts. The input layout term is either a variable (if no layout information is available) or a term carrying detailed layout information as returned by the subterm_positions of read_term/2.