RetractableFrom(S)

coerce.spad line 73 [edit on github]

• S : Type

B is retractable from A means that some elements in A can be converted into elements of B and any element of B can be converted into an element of A.

coerce : % -> S

from CoercibleTo(S)

retract : S -> %

retract(a) transforms a into an element of % if possible. Error: if a cannot be made into an element of %.

retractIfCan : S -> Union(%, "failed")

retractIfCan(a) transforms a into an element of % if possible. Returns "failed" if a cannot be made into an element of %.

CoercibleTo(S)