opts.tolerance (relative, bSI #418 — e.g. 1e-6) replaces the absolute
1e-9 epsilon below for eq/ne and widens gte/lte to accept a value
within tolerance of the boundary; gt/lt stay strict (a tolerant strict
inequality would let a value equal to the boundary pass both gt and its
own negation's neighbour). Omitted opts/tolerance = today's absolute-
epsilon behaviour, unchanged.
opts.tolerance(relative, bSI #418 — e.g.1e-6) replaces the absolute1e-9epsilon below foreq/neand widensgte/lteto accept a value within tolerance of the boundary;gt/ltstay strict (a tolerant strict inequality would let a value equal to the boundary pass bothgtand its own negation's neighbour). Omittedopts/tolerance= today's absolute- epsilon behaviour, unchanged.