# Symbolics build function failed for Matrix

**URL:** <https://discourse.julialang.org/t/symbolics-build-function-failed-for-matrix/126828>\
**Category:** General Usage\
**Tags:** symbolic, symbolics\
**Created:** [March 11, 2025, 8:49pm UTC](https://discourse.julialang.org/t/symbolics-build-function-failed-for-matrix/126828 "2025-03-11T20:49:30Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Veenty](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/veenty/32/50940_2.png) [@Veenty](https://discourse.julialang.org/u/Veenty)\
**Post date:** [March 11, 2025, 8:49pm UTC](https://discourse.julialang.org/t/symbolics-build-function-failed-for-matrix/126828/1 "2025-03-11T20:49:30Z")

</div>

The following code is not being evaluated at all

```julia
@variables ξ
u_h = [1, ξ]
γ_matrix = rand(ComplexF64, (2,2))
foo = eval.(build_function.(γ_matrix*u_h, ξ))
foo[1](0.) # 0.718261200283448 + 0.7541320221601713ξ + im*(0.11955519784649504 + 0.6025851857044455ξ)

```

No idea what is going on ):

---

<div class="post-metadata">

**Author:** ![Veenty](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/veenty/32/50940_2.png) [@Veenty](https://discourse.julialang.org/u/Veenty)\
**Post date:** [March 11, 2025, 9:13pm UTC](https://discourse.julialang.org/t/symbolics-build-function-failed-for-matrix/126828/2 "2025-03-11T21:13:50Z")

</div>

So even a simpler examples where this fails

```julia
@variables ξ
foo = eval.(build_function.([1im*ξ+ ξ], ξ))
foo(0.0)# ξ + im*ξ

```