How to 'execute' a table without manually converting i

Hi Folks,
The UNIX shell has a printf command. Here's an example:
printf "A string %s and a number %d" hello 10
The "..." part is called the format string. Following the format string are
arguments. The %s indicates that the first argument (hello) is a string. The
%d indicates that the second argument (10) is a number.
%s is the most basic form. The complete form is: %[flag][width][.precision]s
width can be either a number or *. If it is * then the width is specified by
an argument, e.g.,
printf "A string %10s" hello  <-- print hello in a field width of 10
printf "A string %*s" 15 hello  <-- print hello in a field width of 15
Ditto for precision
printf "A string %*.*s" 10 3 hello  <-- 10 is the width, 3 is the precision,
and the string to be printed is hello.
Suppose the printf command is represented in XML and $arg is a variable that
contains an argument. An XSLT program encounters %...s and must get the
appropriate string from the arguments. If it is a simple %s then the string is
in $arg. If it is %*s then the width is in $arg and the string is in
$arg/following-sibling::argument[1]. If it is %*.*s then the width is in $arg,
the precision is in $arg/following-sibling::argument[1], and the string is in
$arg/following-sibling::argument[2]. Here's a table that describes where to
get the string:
width
precision
location of the string
*
*
$arg/following-sibling::argument[2]
*
number or no precision specified
$arg/following-sibling::argument[1]
number or no width specified
*
$arg/following-sibling::argument[1]
number or no width specified
number or no precision specified
$arg

That, in my opinion, is a beautiful table. I wish that I could put that table
into my XSLT program and instruct the XSLT processor, "Hey, use the table to
get the appropriate string." Alas, as you know, Microsoft Word tables cannot
be embedded into XSLT programs.
Of course I can manually translate that table into a bunch of nested
if-then-else expressions:
if ($width eq '*') then
    if ($precision eq '*') then
        $arg/following-sibling::argument[2]
    else
        $arg/following-sibling::argument[1]
else
    if ($precision eq '*') then
       $arg/following-sibling::argument[1]
   else
       $arg
I suppose that translation is not too complicated. But in a larger table the
likelihood of making mistakes in the translation grows exponentially. I
remember Liam saying (paraphrasing): "Any program longer than 6 lines has
bugs."
Manually translating tables into code is fraught with peril.
There must be a better way!
By "better" I mean more assuredness that the code faithfully/accurately
encodes the table.
So, what I seek from you is this: How do *you* translate tables into code? Do
you have a way that is 100% guaranteed to faithfully/accurately encode the
table?
/Roger