types_power_out

What it is ¶

types_power_out(present) yields exactly one row, with the value true, when the design’s source format classifies power-OUTPUT pins, and zero rows otherwise. Like has_nc_channel, it is a design-capability flag, not a per-entity relation: there is never more than one row, and its presence or absence is the whole signal. A KiCad or gEDA design (whose readers type a regulator output POWER_OUT and a power flag) makes the row appear; an EDIF netlist or an IPC-2581 board (whose grammars carry no power-output type) produces no row.

For hardware engineers ¶

Some formats let you mark a pin as a power SOURCE (a regulator’s output, a power flag), so the tool can tell a rail that has a source from one that does not. EDIF and IPC do not, so a regulator’s output pin reads as a plain input there, indistinguishable from the loads it feeds. This flag says which world you are in. It matters because “this power rail has no source” is only a real finding when the format could have named a source; on EDIF that same net looks sourceless for every switched or derived rail, which is a false alarm, not a defect.

For software engineers ¶

This is a capability probe over the whole design, closer to a feature flag than a row set. Because a rule reads it as types_power_out(?_), an absent row makes the enclosing conjunction yield nothing, so the guard fails closed: on a format that cannot type power outputs, a driver-absence rule produces no findings by construction. That is exactly why power-input-not-driven gates on it (WS3-072): the POWER_IN pin stamp makes supply inputs visible on EDIF, but the source side stays under-typed, so inferring “unpowered” from the absence of a typed driver would false-fire on every switched rail. Absent means “the format cannot say,” treated as “do not fire,” never as “the rail is unpowered.” The gate reads the same capability through the design.types_power_out spec fact; this relation is its queryable twin, so you can ask “is a driver-absence check even sound on this design” before trusting one.

Go projector ¶

typesPowerOutFacts in check/facts.go calls Model.FormatTypesPowerOut(). When it is true the projector returns a single row (subject true); when false it returns nil, so the relation is one row or none, never more. The capability is derived from SourceFormat (false for an edif/ipc prefix), so it needs no precomputed state. Zero rows is the meaningful state, and it is what a gated rule fails closed on.

Datalog ¶

Probe the flag directly (one row true, or empty):

types_power_out(?present) => ?present

Use it as a guard so a driver-absence check runs only where power outputs are typed (a power-input pin with no source reported only when the format could have named the source):

pin.type(?r, ?p, "power_in"), types_power_out(?present) => ?r, ?p