Add a global rule for HeavisideTheta[0]

Question

I would like to define HeavisideTheta[0] and HeavisideTheta[0.] (as apparently Mathematica won't recognize these two as identical) to be always in my notebook identically equal to 1. What would be a quick and clean way to do this instead of constantly having to add rules in my code?

Is it even possible to change the values of a built in function in Mathematica? — Mauricio Fernández, Dec 02 '16 at 10:19
Well if I tell Mathematica to apply the rule to an expression, i.e. /.HeavisideTheta[0]-> 1 it manages to do that. @MauricioLobos — Mirko Aveta, Dec 02 '16 at 10:24
I'd suggest to define a new function with the desired behaviour. You could re-define the existing one with Unprotect and then Protect, but it's not recommended. — , Dec 02 '16 at 11:08
Does $Assumptions = HeavisideTheta[0] == 1 and HeavisideTheta[0] // Simplify work for you? — Mauricio Fernández, Dec 02 '16 at 12:06
@MauricioLobos Assumptions doesn't work. Simplify works but not with HeavisideTheta[0.]. — Mirko Aveta, Dec 02 '16 at 12:25

score 4 · Accepted Answer · answered Dec 02 '16 at 12:31

4

Global assumption for a notebook might be an option

$Assumptions = HeavisideTheta[0] == 1 && HeavisideTheta[0.] == 1;
HeavisideTheta[0]
HeavisideTheta[0] // Simplify
HeavisideTheta[0.]
HeavisideTheta[0.] // Simplify

answered Dec 02 '16 at 12:31

Mauricio Fernández

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Add a global rule for HeavisideTheta[0]

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