format_MESGFeedback.format_MESG : string -> string
Maps argument of HOL_MESG to a string.
The format_MESG function maps a string to a string.
Usually, the input string is the argument of an invocation of
HOL_MESG. format_MESG is the default function
used by MESG_to_string.
Never fails.
> format_MESG "Hello world.";
val it = "<<HOL message: Hello world.>>\n": string
Feedback, Feedback.MESG_to_string,
Feedback.format_ERR,
Feedback.format_WARNING