Initial data commit

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

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+:- 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", "#include <string.h>").
+
+:- 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

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+:- func strdup(string) = string.