x and y can be
distances (InfinitySparseMatrix, BlockedInfinitySparseMatrix,
or DenseMatrix), or they can be optmatch objects.To save space, optmatch objects merely store a hash of the distance
matrix instead of the original object. Any distance objects are hashed before
comparison.
optmatch_same_distance(x, y)Boolean whether the two distance specifications are identical.
A distances (InfinitySparseMatrix,
BlockedInfinitySparseMatrix, or DenseMatrix), or
optmatch object.
A distances (InfinitySparseMatrix,
BlockedInfinitySparseMatrix, or DenseMatrix), or
optmatch object.
Note that the distance is hashed with its call set to NULL.
(This avoids issues where, for example, match_on(Z~X, data=d,
caliper=NULL) and match_on(Z~X, data=d) produce identical matches but
have differing calls.)