Data commit

Task/Use-another-language-to-call-a-function/Mercury/use-another-language-to-call-a-function.mercury

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+:- module query.
+:- interface.
+
+:- pred query(string::in, string::out) is det.
+
+:- implementation.
+
+query(_, "Hello, world!").
+
+:- pragma foreign_export("C", query(in, out), "query").
+
+:- pragma foreign_decl("C",
+"
+#include <string.h>
+int Query (char * Data, size_t * Length);
+").
+:- pragma foreign_code("C",
+"
+int Query (char *Data, size_t *Length) {
+    MR_String input, result;
+    MR_allocate_aligned_string_msg(input, *Length, MR_ALLOC_ID);
+    memmove(input, Data, *Length);
+    query(input, &result);
+    *Length = strlen(result);
+    memmove(Data, result, *Length);
+    return 1;
+}
+").