This built-in predicate outputs a term to an output stream. The output stream must be a text stream that was opened for writing or appending data. The data is written in a form defined by the write-options list [numbervars(false), quoted(true), ignore_ops(true)].
The Prolog flags print_double_quotes and expand_backslash may affect write_canonical/2.
see also: char_conversion/2 current_char_conversion/2 current_op/3 op/3 read/1 read/2 read_term/2 read_term/3 write/1 write/2 write_canonical/2 write_list/1 write_list/2 write_list_goal/2 write_list_goal/3 write_term/2 write_term/3 writeq/1 writeq/2
| Example | |
| write_canonical(X=a). | succeeds with empty substitution and the following data was written to the current output stream: =(X, a) |
| write_canonical('$VAR'(51)). | assume the current output stream has contents: =(X, a) and the current output stream is left as: =(X, a)'$VAR'(51) |
| write_canonical([1,2,3]). | assume the current output stream has contents: =(X, a) and the current output stream is left as: =(X, a).(1, .(2, .(3, []))) |
| Exceptions | |
| stream_or_alias is a variable | an instantiation_error exception is thrown |
| stream_or_alias is neither a variable nor a stream term nor an alias | a domain_error(stream_or_alias, Stream) exception is thrown, the variable Stream is assigned the incorrect stream_or_alias term |
| stream_or_alias is not associated with an open stream | an existence_error(stream, Stream) exception is thrown |
| stream_or_alias is an input stream | a permission_error(output, stream, Stream) exception is thrown |
| stream_or_alias is a binary stream | a permission_error(output, binary_stream, OutputStream) is thrown, the variable OutputStream is assigned the stream which was used as the output stream |