tuesday

tuesday.c

// compile with `gcc -shared -o tuesday.so tuesday.c`

#include <time.h>

int day_of_week()
{
    time_t t;
    time(&t);
    return localtime(&t)->tm_wday;
}

tuesday.idr

module Main
%dynamic "./tuesday.so"

dayOfWeek : IO Int
dayOfWeek = foreign FFI_C "day_of_week" (IO Int)

isItTuesday : IO (Provider ())
isItTuesday = do day <- dayOfWeek
                 pure $ if day == 2 then Provide () else Error "it's not tuesday!!!"

%language TypeProviders
%provide (tuesday : Unit) with isItTuesday

main : IO ()
main = pure tuesday