14.2.3 Construct Layout

In several cases the suggested layout in the Ada Reference Manual includes an extra level of indentation that many programmers prefer to avoid. The affected cases include:

• Record type declaration (RM 3.8)
• Record representation clause (RM 13.5.1)
• Loop statement in case if a loop has a statement identifier (RM 5.6)
• Block statement in case if a block has a statement identifier (RM 5.6)

In compact mode (when GNAT style layout or compact layout is set), the pretty printer uses one level of indentation instead of two. This is achieved in the record definition and record representation clause cases by putting the record keyword on the same line as the start of the declaration or representation clause, and in the block and loop case by putting the block or loop header on the same line as the statement identifier.

The difference between GNAT style -l1 and compact -l2 layout on the one hand, and uncompact layout -l3 on the other hand, can be illustrated by the following examples:

     

     GNAT style, compact layout              Uncompact layout
     
     type q is record                        type q is
        a : integer;                            record
        b : integer;                               a : integer;
     end record;                                   b : integer;
                                                end record;
     
     for q use record                        for q use
        a at 0 range  0 .. 31;                  record
        b at 4 range  0 .. 31;                     a at 0 range  0 .. 31;
     end record;                                   b at 4 range  0 .. 31;
                                                end record;
     
     Block : declare                         Block :
        A : Integer := 3;                       declare
     begin                                         A : Integer := 3;
        Proc (A, A);                            begin
     end Block;                                    Proc (A, A);
                                                end Block;
     
     Clear : for J in 1 .. 10 loop           Clear :
        A (J) := 0;                             for J in 1 .. 10 loop
     end loop Clear;                               A (J) := 0;
                                                end loop Clear;
     

A further difference between GNAT style layout and compact layout is that GNAT style layout inserts empty lines as separation for compound statements, return statements and bodies.

Note that the layout specified by --separate-stmt-name for named block and loop statements overrides the layout defined by these constructs by -l1, -l2 or -l3 option.