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4 A Complete Example To finish off the chapter, a complete example of a FunnelWeb input file is presented. Although unrealistically short, it gives a better idea of what a typical FunnelWeb .fw file looks like.
@!---------------------------------------! @! Start of FunnelWeb Example .fw File ! @!---------------------------------------! @t vskip 40 mm @t title titlefont centre "Powers:" @t title titlefont centre "An Example of" @t title titlefont centre "A Short" @t title titlefont centre "FunnelWeb .fw File" @t vskip 10 mm @t title smalltitlefont centre "by Ross Williams" @t title smalltitlefont centre "26 January 1992" @t vskip 20 mm @t table_of_contents @A@<FunnelWeb Example Program@> This program writes out each of the first @{p@} powers of the first @{n@} integers. These constant parameters are located here so that they are easy to change. @$@<Constants@>==@{@- n : constant natural := 10; -- [1,n] numbers? p : constant natural := 5; -- [1,p]) powers?@} @B Here is the outline of the program. This FunnelWeb file generates a single Ada output file called @{Power.ada@}. The main program consists of a loop that iterates once for each number to be written out. @O@<Power.ada@>==@{@- @<Pull in packages@> procedure example is @<Constants@> begin -- example for i in 1..n loop @<Write out the first p powers@> end loop; end example; @} @B In this section, we pull in the packages that this program needs to run. In fact, all we need is the IO package so that we can write out the results. To use the IO package, we first of all need to haul it in (@{with text_io@}) and then we need to make all its identifiers visible at the top level (@{use text_io@}). @$@<Pull in packages@>@{with text_io; use text_io;@} @B Here is the bit that writes out the first @{p@} powers of @{i@}. The power values are calculated incrementally in @{ip@} to avoid the use of the exponentiation operator. @$@<Write out the first p powers@>@{@- declare ip : natural := 1; begin for power in 1..p loop ip:=ip*i; put(natural'image(ip) & " "); end loop; new_line; end;@} @!---------------------------------------! @! End of FunnelWeb Example .fw File ! @!---------------------------------------!
FunnelWeb's functionality can be split into two parts: a macro preprocessor, and support for typesetting. The reader should be aware that the examples in this manual, constructed as they have been to demonstrate particular features of FunnelWeb, do not present a realistic picture of the best use of the tool. Only the example above comes close.
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