2.5.8. Hard version

Constraint C π‘Žπ‘™π‘ π‘œ is a hard version of constraint C π‘’π‘›π‘‘π‘Ÿπ‘¦ (i.e.,Β constraint C π‘’π‘›π‘‘π‘Ÿπ‘¦ is a soft variant of constraint C π‘Žπ‘™π‘ π‘œ ).

EXAMPLE: As an example, constraint C π‘Žπ‘™π‘ π‘œ = πšŠπš•πš•πšπš’πšπšπšŽπš›πšŽπš—πš is a hard version of constraint C π‘’π‘›π‘‘π‘Ÿπ‘¦ = 𝚜𝚘𝚏𝚝_πšŠπš•πš•πšπš’πšπšπšŽπš›πšŽπš—πš, which restricts the minimum number of variables that should be unassigned in order that all variables take a distinct value.