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(true), quoted(true), ignore_ops(false)].
The Prolog flags print_double_quotes and expand_backslash may affect writeq/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/1 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
| Example | |
| writeq(user_output, X=a). | succeeds with empty substitution and the following data was written to the output stream: (X = a) |
| writeq(user_output, '$VAR'(51)). | assume the current output stream has contents: (X = a) and the current output stream is left as: (X = a)Z1 |
| writeq(user_output, [1,2,3]). | assume the current output stream has contents: (X = a)Z1 and the current output stream is left as: (X = a)Z1[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 |