3.12 Pragma: Indentation

When FunnelWeb expands a macro, it can do so in two ways. First it can treat the text it is processing as a one-dimensional stream of text, and merely insert the body of the macro in place of the macro call. Second, it can treat the text of the macro as a two dimensional object and indent each line of the macro body by the amount that the macro call itself was indented. Consider the following macros.

@$@<Loop Structure@>@{@-
i=1;
while (i<=N)
   @<Loop body@>
endwhile
@}

@$@<Loop body@>@{@-
a[i]:=0;
i:=i+1;@}

Under the regime of no indentation the loop structure macro expands to:

i=1;
while (i<=N)
   a[i]:=0;
i:=i+1;
endwhile

Under the regime of blank indentation the loop structure macro expands to:

i=1;
while (i<=N)
   a[i]:=0;
   i:=i+1;
endwhile

The indentation pragma determines which of these two regimes will be used to expand the macros when constructing the product files. The syntax of the pragma is:

pragma_ident = ps "indentation" s "=" s
               ("blank" | "none")

Its two forms look like this:

@p indentation = blank
@p indentation = none

In the current version of FunnelWeb, the indentation regime is an attribute that is attached to an entire run of Tangle; it is not possible to bind it to particular product files or to particular macros. As a result, it doesn't matter where indentation pragmas occur in the input file or how many there are so long as they are all the same. By default FunnelWeb uses blank indentation.