write_term/3

write_term(@stream_or_alias, ?term, +write_options_list) [ISO]

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 specified write-options list. The possible values of the write options list are:

numbervars
- true: a term of the form '$VAR'(N) where N is an integer is output as a variable name consisting of a capital letter possibly followed by an integer. The capital letter is the (N mod 26)th letter of the alphabet and the integer is N // 26. For instance: '$VAR'(0) is written as A, '$VAR'(1) is written as B, '$VAR'(26) is written as A1.
- false: variable are output with normal syntax. The character sequence starts with an underscore and the remaining characters are the Trinc-Prolog variable identifier.
quoted
- true: each atom and functor is quoted if this would be necessary for the term to be read by read_term/3.
- false: each atom and functor is written as specified by its syntax.
ignore_ops
- true: each compound term is output in functional notation. Neither operator notation nor list notation is used when this write option is in force.
- false: compound terms are output using operator notation or list notation.

The Prolog flags print_double_quotes and expand_backslash may affect write_term/3.

Example
write_term(user_out, X=a, [ignore_ops(true)]).	succeeds with empty substitution and the following data was written to the 'user_out' output stream: =(__1, a)
Y=a + '$VAR'(53), write_term(user_out, Y, [ignore_ops(true), numbervars(true)]).	assume the 'user_out' output stream has contents: =(__1, a) and the 'user_out' output stream is left as: =(__1, a)+a(, B2)

Exceptions
the write options list is a variable	an instantiation_error exception is thrown
the write options list is neither a variable nor a list	a type_error(list, WriteOptions) exception is thrown
an element E of the write options list is a variable	an instantiation_error exception is thrown
an element E of the write options list is neither a variable nor a valid write option	a domain_error(write_option, E) exception is thrown
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

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