# Symbolics with Control Flow

**URL:** <https://discourse.julialang.org/t/symbolics-with-control-flow/93073>\
**Category:** General Usage\
**Tags:** symbolics\
**Created:** [January 17, 2023, 7:35am UTC](https://discourse.julialang.org/t/symbolics-with-control-flow/93073 "2023-01-17T07:35:19Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Daniel\_Lewis](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/daniel_lewis/32/31250_2.png) [@Daniel\_Lewis](https://discourse.julialang.org/u/Daniel_Lewis)\
**Post date:** [January 17, 2023, 7:35am UTC](https://discourse.julialang.org/t/symbolics-with-control-flow/93073/1 "2023-01-17T07:35:19Z")

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hello,  
I’m trying to create a function with `if` condition using a symbolic var:

```julia
using Symbolics
@variables t
params = @parameters F

function f(t)
	if 0≤t<5
        return 1
	end

	if 5≤t<10
        return -1
	end
    
	return 0
end

Q = [F*f(t), 0]

```

The error is at `Q = [F\*f(t), 0]’ :

```julia
ERROR: TypeError: non-boolean (Num) used in boolean context

```

How can I overcome this error?  
thanks in ahead.

---

<div class="post-metadata">

**Author:** ![baggepinnen](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/baggepinnen/32/693_2.png) [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)\
**Post date:** [January 17, 2023, 9:23am UTC](https://discourse.julialang.org/t/symbolics-with-control-flow/93073/2 "2023-01-17T09:23:39Z")

</div>

[Frequently Asked Questions · ModelingToolkit.jl](https://docs.sciml.ai/ModelingToolkit/dev/basics/FAQ/#How-do-I-handle-if-statements-in-my-symbolic-forms)? - " [How do I handle `if` statements in my symbolic forms?](https://docs.sciml.ai/ModelingToolkit/dev/basics/FAQ/#How-do-I-handle-if-statements-in-my-symbolic-forms?)"

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<div class="post-metadata">

**Author:** ![Daniel\_Lewis](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/daniel_lewis/32/31250_2.png) [@Daniel\_Lewis](https://discourse.julialang.org/u/Daniel_Lewis)\
**Post date:** [January 17, 2023, 9:59am UTC](https://discourse.julialang.org/t/symbolics-with-control-flow/93073/3 "2023-01-17T09:59:04Z")

</div>

thank you very much, that solved my issue.