# Correct constraint statement
**URL:** https://discourse.julialang.org/t/correct-constraint-statement/45036
**Category:** Optimization (Mathematical)
**Created:** [August 16, 2020, 11:03am UTC](https://discourse.julialang.org/t/correct-constraint-statement/45036 "2020-08-16T11:03:56Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@mamo](https://discourse.julialang.org/u/mamo)
#### Post date: [August 16, 2020, 11:03am UTC](https://discourse.julialang.org/t/correct-constraint-statement/45036/1 "2020-08-16T11:03:56Z")
In this constraint k goes from 1 to end but with step equal to in “interval” (scalar equal to 20 for example):
‘’‘rawmbal1[r in RAW, **k in 1…end by interval: k==1**],
INV[r,k]=invraw[r,k]-sum(PRD[o,f,p,j,t]\*demraw[p,r] for o in O,f in F, p in PRC[f], j in U, t in k…k+interval-1: ord(o)\<=23 and ord(f)\<=13 and ord(p)\<=45)’‘’
ord(o)\<=23 - takes only 23 elements of an array in consideration
similar with ord(f) and ord(p).
Do you have some suggestion how to make a correct statement in Julia by solving these two issues.
Thanks,
Marco
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### Author:  [@tomerarnon](https://discourse.julialang.org/u/tomerarnon)
#### Post date: [August 16, 2020, 11:12am UTC](https://discourse.julialang.org/t/correct-constraint-statement/45036/2 "2020-08-16T11:12:49Z")
To construct a range that takes a non-1 step size, you can do `1:step:end`. Hope that helps.
Also, [please make it easier to help you](https://discourse.julialang.org/t/psa-make-it-easier-to-help-you/14757)
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### Author:  [@mamo](https://discourse.julialang.org/u/mamo)
#### Post date: [August 16, 2020, 11:22am UTC](https://discourse.julialang.org/t/correct-constraint-statement/45036/3 "2020-08-16T11:22:59Z")
excellent, thank you.