When I tried to build a new version in the same working directory I'd used to build a previous version, I saw build errors. After a few attempts, I remembered that "make clean" might get past the problem. It seems like a nice thing to suggest to everyone who might fall into the same trap.
* Fix typo in documentation for map_values
"map_value(f)" -> "map_values(f)"
* map_value => map_values also in the devolpment manual
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Co-authored-by: Emanuele Torre <torreemanuele6@gmail.com>