Error with AuxKernal: Invalid function, Syntax error: Unknown identifier

[wlindqwister]

Check these boxes if you have followed the posting rules.

• I have consulted the Posting Guidelines.
• I have searched the Discussions Forum and MOOSE Framework Troubleshooting and have not found what I was looking for
• Q&A Getting Started is the most appropriate category for my question (trouble installing, beginner user, ...)

Issue or question about MOOSE

Hello everyone, I'm relatively new with MOOSE and am trying to calculate an auxiliary variable 'density' based off of nodal distance from a boundary using the the NearestNodeDistanceAux aux kernal paired with ParsedAux (one step beyond what is demonstrated here. I keep running into the following error when trying to calculate:

"The following error occurred in the AuxKernel 'density' of type ParsedAux.

Invalid function
distance^2
in ParsedAux density.
Syntax error: Unknown identifier"

Here is the input file I've been using:

[Mesh]
    [file_mesh]
        type = FileMeshGenerator
        file = meshes/1H_test.msh
    []
    [interior_nodeset]
        type = BoundingBoxNodeSetGenerator
        new_boundary = interior_nodeset
        bottom_left = '-0.01 -0.01 -0.01'
        top_right = '1.01 1.01 1.01'
        input = file_mesh
    []
[]

[Variables]
    [./u]
    [../]
[]

[AuxVariables]
    [./distance]
    [../]
    [./penetration]
    [../]
    [./density]
    [../]
[]

[AuxKernels]
    [./nodal_distance_aux]
        type = NearestNodeDistanceAux
        variable = distance
        boundary = interior_nodeset
        paired_boundary = hydrosurf
    [../]
    [./penetration_aux]
        type = PenetrationAux
        variable = penetration
        boundary = interior_nodeset
        paired_boundary = hydrosurf
    [../]
    [./density]
        type = ParsedAux
        variable = density
        coupled_variable = 'distance'
        expression = 'distance^2'
    [../]
[]

[Problem]
    type = FEProblem
    solve = false
[]

[Executioner]
    type = Steady
[]

[Outputs]
    file_base = densityTest1Hole
    execute_on = 'timestep_end'
    exodus = true
[]

I've looked through the examples on the website and I can't find where my syntax is incorrect. Any help would be greatly appreciated!

(Optional) code in question / simulation log / errors

No response

Encountering Errors? Please include diagnostic output

No response

[wlindqwister]

Never mind, I found a small syntax error in ParsedAux that I overlooked. My bad!

[GiudGiud]

EDIT: (I'm replying to another poster who seemed to have deleted their message)

You either have a typo in the expression

Or one of the terms in the expression should be in one of the other parameters that describe what type it is

For example a variable should be specified in coupled_variables, a functor in functor_symbols