I am having trouble understanding how variables are passed in as parameters.

My goal is to create a function

f(logical,x,y,z) = Evaluate [logical(x,y,z)]

From there I should be able to call f(x||y||z, x,y,z)

and it will output (false||false||false).

My current format:

func1[expr_,xval_,yval_,zval] = expr /. {xval->x, yval ->y, zval ->z}

Obviously this is wrong because I have yet to define x,y,z until I call the function. Really just unsure of the format and have no idea where to go.

  • 1
    $\begingroup$ func1 is just ReplaceAll, maybe with Hold or Defer. Try ReplaceAll[Hold[x||y||z],{x->False, y->False, z->False}] or ReplaceAll[Defer[x||y||z],{x->False, y->False, z->False}]. If you want it in function form, just set HoldFirst or HoldAll to the function. $\endgroup$
    – b3m2a1
    Sep 13, 2017 at 4:07
  • $\begingroup$ Why would f[x || y || z, x, y, z] necessarily return False || False || False? If x, y and z were False, it would automatically evaluate to just False (hence @b3m2a1's comment). If x, y and z did not have truth values it would just return unevaluated x || y || z. $\endgroup$ Sep 13, 2017 at 4:57
  • $\begingroup$ Please find a descriptive title for your questions. See the asking guidelines. $\endgroup$
    – Szabolcs
    Sep 13, 2017 at 8:09

1 Answer 1


I would recommend starting in the wolfram documentation for functions. I'm not completely sure what you are trying to do with your inputs, but I believe you want to make a function that evaluates some other function or functions. You could write this as

func1[expr_, x_, y_, z_] := expr[x, y, z];

then create whatever expressions you need to evaluate

equation1[x_, y_, z_] := x + y + z;
equation2[x_, y_, z_] := x^2 + y^2 + z^2;

then pass them both into func1

func1[#, 1, 2, 3] & /@ {equation1, equation2}

For a logical function it is similar. Lets assume you have defined variables somewhere in your book



equation3[a_, b_, c_] := x == a || y == b || z == c;

will check if the inputs a, b, or c are equal to x, y, or z, respectively. So

func1[eq3, 1, 23, 45]

will give you True, since a (1) is equal to x. Finally, to output some array, just make the equation an array:

equation4[a_, b_, c_] := {TrueQ[x == a], TrueQ[y == b], TrueQ[z == c]}


func1[equation4, 1, 2, 3]


{True, False, False}
  • 1
    $\begingroup$ func1[Or, x, y, z] (returns x || y || z) might clarify things for the OP. Also, func1 is essentially Apply. $\endgroup$ Sep 13, 2017 at 5:02

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