Variadic function: Difference between revisions
Add BCPL
MaiconSoft (talk | contribs) m (Added Delphi reference to Free Pascal code) |
Not a robot (talk | contribs) (Add BCPL) |
||
Line 599:
for (i = 1; i <= a[0]; i++) a[i]
}</lang>
=={{header|BCPL}}==
BCPL does not have true variadic functions, however, it is explicitly legal
to pass a function the "wrong" amount of arguments. If fewer arguments are passed
than declared, the rest will remain uninitialized, if too many are passed,
the excess arguments are ignored. Additionally, it is guaranteed that the arguments will be located sequentially
in memory, starting from the first, making it possible to treat the address of the
first argument as if it is in fact an array of arguments.
These two facts together make it easy to declare a "variadic" function by
simply specifying a whole bunch of dummy arguments in the declaration, and then calling
the function later on with however many you happen to need. At least as many arguments as
you declare are guaranteed to make it through, though any more will not necessarily.
This technique is used in the standard library (this is how <code>writef</code>, the
equivalent to C's <code>printf</code>, is defined), and the book <cite>BCPL: The Language
and its Compiler</cite> by BCPL designer Martin Richards (which is as official as it gets)
explicitly introduces this technique.
<lang bcpl>get "libhdr"
// A, B, C, etc are dummy arguments. If more are needed, more can be added.
// Eventually you will run into the compiler limit.
let foo(num, A, B, C, D, E, F, G, H, I, J, K, L, M, N, O) be
// The arguments can be indexed starting from the first one.
for i=1 to num do writef("%S*N", (@num)!i)
// You can pass as many arguments as you want. The declaration above guarantees
// that at least the first 16 arguments (including the number) will be available,
// but you certainly needn't use them all.
let start() be
foo(5, "Mary", "had", "a", "little", "lamb")</lang>
{{out}}
<pre>Mary
had
a
little
lamb</pre>
=={{header|C}}==
| |||