# ERROR: type PeriodicBoundary has no field order

**URL:** <https://discourse.julialang.org/t/error-type-periodicboundary-has-no-field-order/90759>\
**Category:** New to Julia\
**Tags:** question\
**Created:** [November 24, 2022, 4:38pm UTC](https://discourse.julialang.org/t/error-type-periodicboundary-has-no-field-order/90759 "2022-11-24T16:38:18Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![charlie\_echo\_bravo](https://avatars.discourse-cdn.com/v4/letter/c/85f322/32.png) [@charlie\_echo\_bravo](https://discourse.julialang.org/u/charlie_echo_bravo)\
**Post date:** [November 24, 2022, 4:38pm UTC](https://discourse.julialang.org/t/error-type-periodicboundary-has-no-field-order/90759/1 "2022-11-24T16:38:18Z")

</div>

Hello,

I’m teaching myself Julia to solve PDE. As toy problem I am duplication this very simple heat equation problem:  
[Dirichlet boundary conditions](https://github.com/SciML/MethodOfLines.jl/blob/master/docs/src/tutorials/heat.md)

I’m trying to redefine the initial condition from:

```julia
bcs = [u(0, x) ~ cos(x),
        u(t, 0) ~ exp(-t),
        u(t, 1) ~ exp(-t) * cos(1)]

```

to:

```julia
bcs = [u(0, x) ~ cos(π*x),
        u(t, 0) ~ exp(-t),
        u(t, 1) ~ exp(-t) * cos(1)]

```

The first initial condition is not giving me error, but when I use the 2nd initial condition, Julia is giving this error:

```julia
ERROR: type PeriodicBoundary has no field order

```

I did a some investigating and added 1 \* before pi, as shown below.

```julia
bcs = [u(0, x) ~ cos(1*π*x),
        u(t, 0) ~ exp(-t),
        u(t, 1) ~ exp(-t) * cos(1)]

```

This approach somehow solved the problem. My question is why do I need the multiplier?

---

<div class="post-metadata">

**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [November 24, 2022, 8:40pm UTC](https://discourse.julialang.org/t/error-type-periodicboundary-has-no-field-order/90759/2 "2022-11-24T20:40:09Z")

</div>

This just seems to be a bug in the library. I would open an issue on the repo with this information.