Formatted output of terms (not in ISO)

The predicate format(Format,L), which mimics the printf function in C, prints the elements in the list L under the control of Format, which is a string of characters. There are two kinds of characters in Format: normal characters are output verbatim, and control characters format the elements in L. Control characters all start with ~. For example,

      format("~thello~t world~t~a~t~4c~t~4d~t~7f",[atom,0'x,123,12.3])

gives the following output:

      hello    world  atom    xxxx     123        12.300000

The control characters ~a, ~4c,~4d, and ~7f control the output of the atom atom, the character 0'x, the integer 123, and the float 12.3, respectively. The control characters ~t put the data into different columns.

• format(Format,L): Outputs the arguments in the list L under the control of Format.

• format(Stream,Format,L): This is the same as format(Format,L), except that it sends the output to Stream.

The following control characters are supported:

• ~~: Prints ~.

• ~N|: Specifies a new position for the next argument.

• ~N+: This is the same as ~N|.

• ~a: Prints the atom without quoting. An exception is raised if the argument is not an atom.

• ~Nc: The argument must be a character code. Outputs the argument N times. Outputs the argument once if N is missing.

• ~Nf,~Ne, ~Ng: The argument must be a number. The C function printf is called to print the argument with the format "%.Nf", "%.Ne", and "%.Ng", respectively. ".N" does not occur in the format for the C function if N is not specified in the Prolog format.

• ~Nd: The argument must be a number. N specifies the width of the argument. If the argument occupies more than N spaces, then enough spaces are filled to the left of the number.

• ~Nr: The argument must be an integer. Prints the integer as a base N integer, where $2 \leq N \leq 36$. The letters `a-z' denote digits larger than 9.
• ~NR: The argument must be an integer. Prints the integer as a base N integer, where $2 \leq N \leq 36$. The letters `A-Z' denote digits larger than 9.

• ~Ns: The argument must be a list of character codes. Exactly N characters will be printed. Spaces are filled to the right of the string if the length of the string is less than N.

• ~k: Passes the argument to write_canonical/1.

• ~p: Passes the argument to print/1.

• ~q: Passes the argument to writeq/1.

• ~w: Passes the argument to write/1.

• ~Nn: Prints N new lines.

• ~t: Moves the position to the next column. Each column is assumed to be 8 characters long.

• ~@: Interprets the next argument as a goal, and executes it.