peek-char obtains the next character in input-stream
without actually reading it, thus leaving the character
to be read at a later time. It can
also be used to skip over and discard intervening
characters in the input-stream
until a particular character is found.
If peek-type is not supplied or nil,
peek-char returns the next character to be read from
input-stream, without actually removing it from
The next time input is done from input-stream, the character will still
If peek-type is t,
then peek-char skips over whitespace2 characters,
but not comments,
and then performs the peeking operation on the next
The last character examined, the one that starts an object,
is not removed from input-stream.
If peek-type is a character,
then peek-char skips
over input characters until a character that
is char= to that character is found;
that character is left in input-stream.
If an end of file2 occurs and eof-error-p is false,
eof-value is returned.
If recursive-p is true,
this call is expected to be embedded in a higher-level call to read
or a similar function used by the Lisp reader.
When input-stream is an echo stream,
characters that are only peeked at are not echoed. In the
case that peek-type is not nil,
the characters that are passed by peek-char
are treated as if by read-char,
and so are echoed unless they have been marked otherwise by unread-char.