Time for an 2014 update…

Task/Call-a-foreign-language-function/Julia/call-a-foreign-language-function.julia

@@ -0,0 +1,7 @@
+julia> p = ccall(:strdup, Ptr{Uint8}, (Ptr{Uint8},), "Hello world")
+Ptr{Uint8} @0x000000011731bde0
+
+julia> bytestring(p) # convert pointer back to a native Julia string
+"Hello world"
+
+julia> ccall(:free, Void, (Ptr{Uint8},), p)

Task/Call-a-foreign-language-function/Mercury/call-a-foreign-language-function-1.mercury

@@ -0,0 +1,23 @@
+:- module test_ffi.
+
+:- interface.
+
+:- import_module io.
+
+:- pred main(io::di, io::uo) is det.
+
+:- implementation.
+
+% The actual FFI code begins here.
+:- pragma foreign_decl("C", "char *strdup(const char *s);").
+
+:- func strdup(string::in) = (string::out) is det.
+:- pragma foreign_proc("C", strdup(S::in) = (SD::out),
+                       [will_not_call_mercury, not_thread_safe, promise_pure],
+                       "SD = strdup(S);").
+% The actual FFI code ends here.
+
+main(!IO) :-
+  io.write_string(strdup("Hello, worlds!\n"), !IO).
+
+:- end_module test_ffi.

Task/Call-a-foreign-language-function/Mercury/call-a-foreign-language-function-2.mercury

@@ -0,0 +1 @@
+:- func strdup(string) = string.

Task/Call-a-foreign-language-function/Prolog/call-a-foreign-language-function-1.pro

@@ -0,0 +1,2 @@
+:- module(plffi, [strdup/2]).
+:- use_foreign_library(plffi).

Task/Call-a-foreign-language-function/Prolog/call-a-foreign-language-function-2.pro

@@ -0,0 +1,20 @@
+#include <string.h>
+#include <stdio.h>
+#include <SWI-Prolog.h>
+
+static foreign_t pl_strdup(term_t string0, term_t string1)
+{
+  char *input_string, *output_string;
+
+  if (PL_get_atom_chars(string0, &input_string))
+  {
+    output_string = strdup(input_string);
+    return PL_unify_atom_chars(string1, output_string);
+  }
+  PL_fail;
+}
+
+install_t install_plffi()
+{
+  PL_register_foreign("strdup", 2, pl_strdup, 0);
+}

Task/Call-a-foreign-language-function/Prolog/call-a-foreign-language-function-3.pro

@@ -0,0 +1 @@
+$ swipl-ld -o plffi -shared plffi.c

Task/Call-a-foreign-language-function/Prolog/call-a-foreign-language-function-4.pro

@@ -0,0 +1,15 @@
+?- [plffi].
+% plffi compiled into plffi 0.04 sec, 1,477 clauses
+true.
+
+?- strdup('Booger!', X).
+X = 'Booger!'.
+
+?- strdup(booger, X).
+X = booger.
+
+?- strdup(booger, booger).
+true.
+
+?- X = booger, strdup(booger, X).
+X = booger.