A.29 library(writef): Old-style formatted write

copyright

Copied from Edinburgh C-Prolog. Original version by Byrd, changed many times since.

This library provides writef/1 and friends. These predicates originate from Edinburgh C-Prolog and and provided for compatibility purposes. New code should use format/1, format/2 and friends, which are currently supported by more Prolog implementations.

The writef-family of predicates conflicts with the modern character-escapes flag about the interpretation of \-sequences. This can be avoided by

1. Disable character escapes (not recommended unless one wants to run really outdated code unmodified).
2. Double the \ for conflicting interpretations
3. Use ISO compliant alternatives for conflicting interpretations

[det]writef(+Format)

[det]writef(+Format, +Arguments)

Formatted write to the current_output. Format is a format specifier. Some escape sequences require arguments that must be provided in the list Arguments. There are two types of escape sequences: special characters start with \ and include arguments start with %. The special character sequences are:

\n	Output a newline character
\l	Output a line separator (same as \n)
\r	Output a carriage-return character (ASCII 13)
\t	Output a TAB character (ASCII 9)
\\	Output \
\%	Output %
\nnn	Output character <nnn>. <nnn> is a 1-3 decimal number

Escape sequences to include arguments from Arguments. Each time a %-escape sequence is found in Format the next argument from Arguments is formatted according to the specification.

%t	print/1 the next item (mnemonic: term)
%w	write/1 the next item
%q	writeq/1 the next item
%d	display/1 the next item
%n	Put the next item as a character
%r	Write the next item N times where N is the second item (an integer)
%s	Write the next item as a String (so it must be a list of characters)
%f	Perform a ttyflush/0 (no items used)
%Nc	Write the next item Centered in N columns.
%Nl	Write the next item Left justified in N columns.
%Nr	Write the next item Right justified in N columns.

deprecated

New code should use format/1, format/2, etc.

[det]swritef(-String, +Format)

[det]swritef(-String, +Format, +Arguments)

Use writef/1 or writef/2 and write the result to a string. Note that this is a string in the sense of string_codes/2, not a list of character(-code)s.

deprecated

. See format/2,3 and/or with_output_to/2.