Availability:built-in

[ISO]peek_byte(-Byte)

[ISO]peek_byte(+Stream, -Byte)

[ISO]peek_code(-Code)

[ISO]peek_code(+Stream, -Code)

[ISO]peek_char(-Char)

[ISO]peek_char(+Stream, -Char)

Read the next byte/code/char from the input without removing it. These predicates do not modify the stream's position or end-of-file status. These predicates require a buffered stream (see set_stream/2) and raise a permission error if the stream is unbuffered or the buffer is too small to hold the longest multi-byte sequence that might need to be buffered.