Extending endpoint-polarized detector words #
The ordered-word filtration grows a word at its source endpoint. This file packages its two legal one-letter extensions: a compatible incoming arrow is prefixed positively, while a compatible outgoing arrow is prefixed with its formal inverse. Both operations preserve the target polarization and increase word length strictly.
The signs of a word read from its fixed target back toward its source. Source extension appends one Boolean to this list.
Instances For
Prefix the compatible incoming ordinary arrow to an endpoint word.
Instances For
Prefix the formal inverse of the compatible outgoing ordinary arrow to an endpoint word.
Instances For
The interval of a positive source extension lies entirely below the lower endpoint of its parent interval.
The interval of a negative source extension lies entirely above the upper endpoint of its parent interval.
Every word whose path reaches the positive source extension of C after
an arbitrary source prefix has its whole interval below C⁻.
Every word whose path reaches the inverse source extension of C after
an arbitrary source prefix has its whole interval above C⁺.
Every nontrivial endpoint word is obtained, according to its first-letter sign, from a shorter endpoint word by one of the two source extensions.
An endpoint word of length zero is the fixed polarized vertex word.
For fixed target and polarization, the signs read from target to source determine the whole endpoint word.
If the route-sign word of C is an initial segment of that of D, then
the literal path of C is a target-side suffix of the literal path of D.
The extra source-side path is returned explicitly.
Every initial segment of an endpoint word's route signs is itself realized by a target-side endpoint word, and the remaining signs come from the explicit source prefix.
Every endpoint word in the positive branch below C has its interval
below the lower endpoint of C.
Every endpoint word in the inverse branch above C has its interval
above the upper endpoint of C.