why sd() can be applied to character vector?

Hi there,

In the following example, sd() can be applied to a character vector.
However, mean() can not be run in a similar way. Why?

I have read sd() man page, however, I don't find information about that
behavior.

x <- as.character(1:10)
sd(x)

[1] 3.02765

mean(x)

[1] NA
Warning message:
In mean.default(x) : argument is not numeric or logical: returning NA

Practically, I see

$R_HOME/src/library/stats/src/cov.c:633 has

x = PROTECT(coerceVector(x, REALSXP));

which seems to be responsible for the behavior you note (eventually
calling $R_HOME/src/main/util.c:1463), but mean.default catches the
character case early and returns NA_real_.

None of that explains the reasoning however and it does seem a little anomalous

Cheers,
Michael