3.7.67. Costas arrays

A constraint that allows for expressing the Costas arrays problem. A Costas array is a permutation p 1 ,p 2 ,β‹―,p n of n integers 1,2,β‹―,n such that βˆ€Ξ΄βˆˆ[1,n-2],βˆ€i∈[1,n-Ξ΄-1],βˆ€j∈[i+1,n-Ξ΄]:p i -p i+Ξ΄ β‰ p j -p j+Ξ΄ . A.Β Vellino compares in Β [Vellino90] three approaches respectively using Prolog, Pascal and CHIP for solving the Costas arrays problem. In fact the weaker formulation βˆ€Ξ΄βˆˆ[1,⌊n-1 2βŒ‹],βˆ€i∈[1,n-Ξ΄-1],βˆ€j∈[i+1,n-Ξ΄]:p i -p i+Ξ΄ β‰ p j -p j+Ξ΄ was shown to be equivalent to the original one inΒ [Chang87].