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Dealing with pairs imported as rationals

Douglas Kubler
Posted 5 years ago
POSTED BY: Douglas Kubler
8 Replies
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Updating Name
Updating Name
Posted 5 years ago

You're right, the the my n_Rational definition is ignored and defaults to your global. It only looks like it works as intended by passing tests. I'm back to wondering if a parameter can ever be (1) a Rational type and (2) unreduced.
POSTED BY: Updating Name
Rohit Namjoshi
Rohit Namjoshi
Posted 5 years ago

It seems only if it is passed in an unreduced form

ClearAll@f
f[r_Rational] := r
f[Internal`RationalNoReduce[2, 4]]
(* 2/4 *)
POSTED BY: Rohit Namjoshi
Douglas Kubler
Douglas Kubler
Posted 5 years ago
POSTED BY: Douglas Kubler

Works even with the explicit overloading

No, I am afraid it does not! With

score[n_Rational] := ...

it just echoes the input. You probably should do a Clear[score]
POSTED BY: Henrik Schachner

One way might be:

Attributes[score] = HoldAll;
score[n_] := score @@ List[Numerator[Unevaluated@n], Denominator[Unevaluated@n]]
score[1112/1122]
(*   Out:  score[1112,1122]   *)
POSTED BY: Henrik Schachner
Douglas Kubler
Douglas Kubler
Posted 5 years ago

I don't get it. The function score has one parameter. Your function expects two values.
POSTED BY: Douglas Kubler
Rohit Namjoshi
Rohit Namjoshi
Posted 5 years ago

It has to be two values to prevent evaluation. You would have to do something like

ClearAll@score
Attributes[score] = HoldFirst;

score[r_] := Hold@r /. Times[n_, Power[d_, -1]] :> Internal`RationalNoReduce[n, d] // 
             ReleaseHold

score[1112/1122]
(* 1112/1122 *)
POSTED BY: Rohit Namjoshi
Rohit Namjoshi
Rohit Namjoshi
Posted 5 years ago

From this MSE post.

Internal`RationalNoReduce[1112, 1122]
(* 1112/1122 *)

Use it in your score function.
POSTED BY: Rohit Namjoshi
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