Insert character by its Unicode name

Question

From the documentation of insert-char, I cannot see why

(insert-char "GREEK SMALL LETTER EPSILON")

doesn't work. Is there a non-interactive way to insert a character given its Unicode name?

Answer 1

From the documentation of insert-char, I cannot see why

(insert-char "GREEK SMALL LETTER EPSILON")

doesn't work.

It doesn't work because insert-char understands Unicode character names only when called interactively (e.g. via C-x8RET or M-xinsert-charRET), as stated in its docstring:

Interactively, prompt for CHARACTER.  You can specify CHARACTER in one
of these ways:

 - As its Unicode character name, e.g. "LATIN SMALL LETTER A".
   Completion is available; if you type a substring of the name
   preceded by an asterisk ‘*’, Emacs shows all names which include
   that substring, not necessarily at the beginning of the name.

 - As a hexadecimal code point, e.g. 263A.  Note that code points in
   Emacs are equivalent to Unicode up to 10FFFF (which is the limit of
   the Unicode code space).

 - As a code point with a radix specified with #, e.g. #o21430
   (octal), #x2318 (hex), or #10r8984 (decimal).

The interactive spec of insert-char delegates to read-char-by-name for Unicode name completion and translation to the corresponding character code.

When insert-char is called from Lisp, its first argument CHARACTER should satisfy the predicate characterp.

Is there a non-interactive way to insert a character given its Unicode name?

There are multiple ways; here's one for Emacs 26 and subsequent versions:

(insert (char-from-name "GREEK SMALL LETTER EPSILON"))

Here's another for earlier Emacs versions:

(insert (cdr (assoc "GREEK SMALL LETTER EPSILON" (ucs-names))))