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sum constraint
Learn sum constraint in Prolog through a focused explanation, a dedicated construct-specific example, an engineering boundary, and a mastery check.
sum constraint is an atomic Prolog topic inside Constraints. This lesson focuses on how the sum constraint construct is written, what it changes, and when it is the right tool.
Trace the example line by line. Identify the exact syntax for sum constraint, the input state before it runs, and the resulting value, control flow, database state, hardware behavior, or runtime effect afterward. Neighboring lessons use different constructs rather than renamed copies of this one.
Topic-specific example
:- use_module(library(clpfd)).
total(Vs,S) :- Vs ins 0..100, sum(Vs,#=,S).For sum constraint, test the boundary that belongs to this exact feature rather than a generic failure case. Check invalid or empty input, NULL/unknown state, numeric limits, transaction or exception behavior, synthesis/runtime constraints, ownership/permission rules, or backtracking/control-flow effects where they apply.