Would an EcoTerm make sense?

[pchampin]

This question is a spin-off of damooo's comment on #160

As a side-note, more than ArcTerm, it would be great to have an EcoTerm using EcoString . EcoString has phenomenal properties. It is cheap to clone. And can also be mutable (clone-on-write), and can have small strings (upto 15 bytes) inlined without allocation.

That's an interesting point. We could add this in sophia_term, but I have to say I am not entierly convinced. IIUC, the selling points of EcoString are:

• mutability, but Sophia terms are not expected to be mutable;
• allocation-free small strings, but many Sophia terms (IRIs in particular) are actually too long to benefit from this (but ok, typical blank node IDs and numeric literals could benefit from this...)