has_floating_substituents: Detect Floating Substituents

In glyrepr: Representation for Glycan Compositions and Structures

Detect Floating Substituents

Description

Test whether each glycan structure contains one or more substituents whose parent residue is unresolved.

Usage

has_floating_substituents(x)

Arguments

x	A glycan_structure() vector or a glycan igraph.

Details

In the glyrepr IUPAC extension, floating substituents appear in braces before the main glycan. ⁠{6S}<main>⁠ allows every feasible residue in the complete structure to carry the substituent, ⁠{6S|1,2}<main>⁠ restricts it to complete-sequence nodes 1 and 2, and ⁠{?S}<main>⁠ also leaves the carbon position unknown. Residue nodes in floating blocks are counted before the main glycan; substituent blocks contribute no node indices.

Internally, unresolved substituents are stored in the floating_substituents graph attribute. It is a list with one entry per substituent. Each entry contains a canonical substituent token and an integer parents vector of candidate graph vertex indices. An empty vector means every feasible residue vertex is a candidate.

A singleton candidate set is normalized into that vertex's ordinary sub attribute. This also happens whenever chemistry leaves only one feasible residue in the complete structure. structure_floating_substituents() exposes the metadata as a normalized table.

Value

A logical vector with the same length and names as vector input, or a logical scalar for graph input. Missing structures produce NA.

See Also

structure_floating_substituents(), has_floating_parts(), as_glycan_structure()

Examples

glycans <- as_glycan_structure(c(
  floating = "{6S}Gal(a1-3)Gal(a1-",
  restricted = "{6S|1,2}Gal(a1-3)Glc(a1-3)Man(a1-",
  ordinary = "Gal6S(a1-"
))
has_floating_substituents(glycans)

glyrepr documentation built on Sept. 22, 2026, 5:09 p.m.