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replacement - Change Operator Precedence of --> operator



I am trying to use --> operator with highest precedence


Unprotect[LongRightArrow];
LongRightArrow[obj_,property_]:=obj[ToString[property]];
Protect[LongRightArrow];

With this I can do basic operations like accessing properties of an association


In:=  obj = <|"a" -> {2, 3}, "b" -> 5|>
Out:= <|"a" -> {2, 3}, "b" -> 5|>
In:= obj⟶a
Out:= {2, 3}


However when I try to access elements of list in obj-->a Part takes higher precedence. Same applies for operator ^.


In:=  obj⟶a[[1]]
Out:= Missing["KeyAbsent", "a[[1]]"]
In:= obj⟶a^2
Out:= Missing["KeyAbsent", "2 a"]

Answer



How about overloading the LongRightArrow with a special rule for Part[...] as the second argument?


Unprotect[LongRightArrow];
SetAttributes[LongRightArrow, HoldRest]

LongRightArrow[obj_, property_] := obj[ToString[property]];
LongRightArrow[obj_, Part[property_, partspec__]] :=
Part[LongRightArrow[obj, property], partspec];
Protect[LongRightArrow];
obj = <|"a" -> {2, 3}, "b" -> 5|>
obj⟶a
obj⟶a[[1]]


<|"a" -> {2, 3}, "b" -> 5|>

{2, 3}
2

Chip Hurst was quicker than I to show the generalization


LongRightArrow[obj_, head_[f_, args__]] := head[LongRightArrow[obj, f], args]

So I'll just take one more step to handle unary postfix operators, such as ! (Factorial). Trivial by replacing args__ with args___:


LongRightArrow[obj_, head_[f_, args___]] := head[LongRightArrow[obj, f], args]

Now



obj⟶a!


{2, 6}

EDIT
Re the comment:


obj⟶a⟶b

is equivalent to



LongRightArrow[obj, a, b]

while the desired behavior is


LongRightArrow[LongRightArrow[obj, a], b]

Well, obviously, that's exactly what we should tell Mathematica, it can't guess that for us.


LongRightArrow[obj_, a_, b__] := LongRightArrow[LongRightArrow[obj, a], b]
obj⟶a⟶b⟶b⟶b⟶b⟶b



 (((((obj⟶a)⟶b)⟶b)⟶b)⟶b)⟶b

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