Create local alias for variable

Question

I have a function whose parameters are passed "by reference"

Clear[foo]
SetAttributes[foo, HoldFirst]
foo[t_] := t = 10

Is it possible to create an alias for t within foo, so inside the function I can call it something else? I'm looking for something like

foo[t_] := With[{k = t}, k = 10]

But instead of With I want something that keeps t unevaluated until inside the function body.

Kuba · Accepted Answer · 2018-05-09 08:21:23Z

6

Undocumented but very useful, it is exactly what With[{ k := t }, ...] will do:

Clear[foo]
SetAttributes[foo, HoldFirst]
foo[t_] := With[{k := t}, k++ ]

a=5;
foo[a];
a

6

I use it a lot, read more in:

A more documented approach:

ClearAll[foo]
SetAttributes[foo, HoldFirst]
foo[t_] := Module[{k}, Unevaluated[k++] /. k :> t]

answered May 9, 2018 at 6:50

Kuba

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