Runtime conversion source for configured posit quires

A quire is an exact accumulator rather than another rounded floating-point destination. Ordinary words decode to rationals and the reserved word decodes to NaR, so configured quires participate as exact conversion sources. No destination quantizer is installed without an explicit grid and overflow policy.

@[instance_reducible]

instance FloatLib.Floats.ExecFloat.Posit.Quire.Conversion.exactDecoder {format : Formats.Posit.Format} : ExactDecoder (Formats.Posit.Quire.Model format) ℚ

A configured quire exposes its complete exact rational or NaR observation.