The srfi doc states that, if the same key appears more than once in those constructors,

the earlier one takes precedence.

The reference implementation appears to disagree, though, for it just

applies mapping-set in order, so the earlier one will be replaced by the

latter one. (I haven't run the code so pardon me if it is my misunderstanding.)

It may be defined so that it is consistent with alist->mapping. But

earlier-takes-precedence rule may cost extra lookup per item unless the

underlying map data structure provides "insert only when it is a

new key" operation.

Personally, I prefer 'mapping' and 'mapping-unfold' be latter-takes-precedence,

for in the mental model I imagine they first construct an empty mapping and

then applying mapping-set in order, just as the current reference implementation.

BTW, in srfi-125, varargs constructor 'hash-table' specifies it's an error to have

the same key more than once, whereas 'hash-table-unfold' doesn't mention

the case.