low-level-structure.md
In glyrepr: Representation for Glycan Compositions and Structures

empty floating metadata preserves the validation contract

Code
  validate_glycan_graph(graph)
Condition
  Error in `normalize_floating_parts()`:
  ! Graph attribute floating_parts must be a list.

validate_glycan_graph reports invalid input

Code
  validate_glycan_graph(graph)
Condition
  Error in `validate_glycan_graph()`:
  ! Glycan structure must be directed.

graph_to_iupac generates one string from one graph

Code
  graph_to_iupac(list(graph))
Condition
  Error in `graph_to_iupac()`:
  ! Assertion on 'graph' failed: Must inherit from class 'igraph', but has class 'list'.

unannotated forests remain invalid

Code
  validate_glycan_graph(graph)
Condition
  Error in `validate_floating_graph_shape()`:
  ! Glycan structure must be an out tree.

new_glycan_structure checks graph lookup integrity

Code
  new_glycan_structure(iupac, list(graph))
Condition
  Error in `new_glycan_structure()`:
  ! `graphs` must have unique, non-missing IUPAC-condensed names.

Code
  new_glycan_structure("missing-key", stats::setNames(list(graph), iupac))
Condition
  Error in `new_glycan_structure()`:
  ! `graphs` does not contain every structure in `iupac`.
  x Missing graph: "missing-key".