# How to write a sum constraint in JuMP with condition
**URL:** https://discourse.julialang.org/t/how-to-write-a-sum-constraint-in-jump-with-condition/56269
**Category:** Optimization (Mathematical)
**Tags:** jump
**Created:** [March 1, 2021, 5:49pm UTC](https://discourse.julialang.org/t/how-to-write-a-sum-constraint-in-jump-with-condition/56269 "2021-03-01T17:49:21Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@GraceMabele](https://discourse.julialang.org/u/GraceMabele)
#### Post date: [March 1, 2021, 5:49pm UTC](https://discourse.julialang.org/t/how-to-write-a-sum-constraint-in-jump-with-condition/56269/1 "2021-03-01T17:49:21Z")
Hi,
I am having trouble writing the following constraint in JuMP
I currently have it written as below but it is not returning the desired output.
```julia
@constraints model begin
constraint_1[n in n],
sum(w[i,n,np] for i in Ij for np in 1:length(n) if n <= np <= (n+d) ) <= 1.0
end
```
where np is n’
Could someone please assist with the correct syntax?
---
### Author:  [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)
#### Post date: [March 1, 2021, 5:56pm UTC](https://discourse.julialang.org/t/how-to-write-a-sum-constraint-in-jump-with-condition/56269/2 "2021-03-01T17:56:36Z")
A simple rule is that everything at the right of the ∀ (universal quantifier, \forall) should be in your `constraint_name[...]` clause. so:
```julia
@constraints model begin
constraint_1[n in n, j in j],
sum(w[i,n,np] for i in I[j] for np in n:(n+d)) <= 1.0
end
```
Also, please stop using Sets with lowercase letters and iterate over them with the same lowercase letters, this is bad style.
---
### Author:  [@GraceMabele](https://discourse.julialang.org/u/GraceMabele)
#### Post date: [March 1, 2021, 6:10pm UTC](https://discourse.julialang.org/t/how-to-write-a-sum-constraint-in-jump-with-condition/56269/3 "2021-03-01T18:10:21Z")
Noted and thank you. It worked.
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [March 1, 2021, 7:03pm UTC](https://discourse.julialang.org/t/how-to-write-a-sum-constraint-in-jump-with-condition/56269/4 "2021-03-01T19:03:58Z")
To clarify why it’s bad style, if you have `[n in n, j in j]` instead of `[n in N, j in J]`, and you have something in the first constraint like `for np in 1:length(n)`, it is using `length(n)` and not `length(N)`.
---
### Author:  [@GraceMabele](https://discourse.julialang.org/u/GraceMabele)
#### Post date: [March 1, 2021, 8:30pm UTC](https://discourse.julialang.org/t/how-to-write-a-sum-constraint-in-jump-with-condition/56269/5 "2021-03-01T20:30:11Z")
I see. i have made the changes and it helped with other errors I was encountering. Thank you