net.rail

What it is ¶

net.rail(net) yields one row per net the engine treats as a power or ground rail. It covers both polarities, so a supply net (+5V, VCC, 3V3) and a ground net (GND, VSS) both answer net.rail. A net qualifies when it is asserted-driven (a PWR_FLAG or equivalent directive), carries the design-wide global attribute, or its name reads as a rail or ground name and it is not a regulator’s own feedback, switching, control or gate-drive node.

net.ground is the ground-only subset of this relation. Every net.ground row is also a net.rail row, while a supply rail answers net.rail and not net.ground. So net.rail(?n), not net.ground(?n) isolates the supply rails.

For hardware engineers ¶

These are the distribution nets, the ones a design taps rather than routes point-to-point. During a review you query net.rail to check that a rule’s rail set matches your intent. A signal net that shows up here either has a name that collides with a supply convention, or was marked driven when it should not be. A protection or pull-up check also needs this join, because many connectivity rules ask “does this signal reach a rail”.

For software engineers ¶

A rail is a global singleton in the design graph (see the analogy guide). Everything tied to +5V is one electrical node. A reachability walk must not follow an edge into it, or the whole graph collapses into one component. net.rail is the name of that singleton set. The relation is a filtered projection over Nets(), so rows are 1:1 with nets that pass the rail predicate. An empty result means the read found no driven, global, or rail-named net.

Go projector ¶

railFacts in stdlib/relations/facts.go walks Model.Nets() and emits a row for each net where Model.IsPowerRail(name) holds. core/check/locate.go defines IsPowerRail, and it ORs four conditions, the power_driven attribute, the global attribute, IsGroundNet, and IsRailNet. IsGroundNet and IsRailNet both read the model’s naming lexicon, and IsRailNet subtracts regulator-internal nets. One row per rail net; empty when the design has no rail-named, global, or asserted-driven net.

Datalog ¶

List every power or ground rail:

net.rail(?n) => ?n

Find the components sitting on a rail (the loads and sources on power distribution):

net.rail(?n), component.net(?r, ?n) => ?r