# Why does OperatorApplied by default reverse the arguments?

Perhaps this is just one of those Mathematica curiosities, but I'd like to know why by default

OperatorApplied[f][x][y] === f[y,x]


versus the more usual way one would expect it to work,

OperatorApplied[f,2][x][y] === f[x,y]

• Presumably to be consistent with the behavior of the function to be phased out, i.e., Curry. OperatorApplied[f][x][y] === Curry[f][x][y] and OperatorApplied[f,2][x][y] === Curry[f,2][x][y] Mar 20, 2020 at 15:41
• Just for the sake of completeness: OperatorApplied[f, 2][x][y] === CurryApplied[f, 2][x][y] Mar 20, 2020 at 21:40

While common it is not absolute e.g. Replace and TuringMachine have operator forms with first argument type (rules,rule) that correspond to different positions (second, first) in the original function.
• Ok, good - thanks for confirming. At a deeper level, OperatorApplied seems to be the more "practical wing" of CurryApplied which seems to be being reserved for more fundamental work associated with combinators etc. On the other hand, the only difference between the two functions seems to be in their respective operator forms? (b.t.w. the naming with trailing Applied's is v.nice - captures intuitively the moment of resolving). Mar 22, 2020 at 3:02