/. can be used to replace variables but how can one replace operators.
For example in a * b, * can be replaced by + or x or / etc. Is there some function to achieve this?
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3 Answers
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Perhaps use the full names for the operators:
a * b /. Times -> Plus
a + b
answered Apr 7, 2013 at 9:26
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FullForm prints the expression with no special syntax (e.g. Plus instead of +).
FullForm[a*b]
(* Times[a, b] *)
So you change the expression's head.
Table[fun @@ (a*b),
{fun, {Plus, Subtract, Divide, Dot, Cross}}]
(* {a + b, a - b, a/b, a.b, a\[Cross]b} *)
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Just to complement: be careful when your symbols have values already assigned.
Compare:
a = 2; b = 3; rule = Plus -> Times;
a + b /. rule
ReleaseHold[Hold[a + b] /. rule]
Unevaluated[a + b] /. rule
Defer[a + b] /. rule
(*
5
6
6
a b
*)
answered Apr 7, 2013 at 16:53
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c = Defer[a + b];How comec + 3doesn't return 8? $\endgroup$– BoLeCommented Apr 7, 2013 at 17:09 -
$\begingroup$ @BoLe: execute
c + 3 // FullFormand see. $\endgroup$ Commented Apr 7, 2013 at 17:16
Fu[a_, b_, o_] := Module[{}, Unevaluated[a + b] /. Plus -> o]; Fu[4, 2, Times]$\endgroup$