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This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 2021-2022 Paulo Moura <pmoura@logtalk.org> SPDX-FileCopyrightText: 2021 Jacinto Dávila Quintero <jdavila@optimusprime.ai> SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

tsv

The tsv library provides predicates for reading and writing TSV files and streams:

https://www.iana.org/assignments/media-types/text/tab-separated-values

The main object, tsv/2, is a parametric object allowing passing two options: header handling (keep or skip) and comment handling (false or true). When comment handling is true, lines starting with the # character are skipped when reading files and streams.

The tsv/1 parametric object is kept for backward compatibility and extends tsv/2 by setting the comments option to false. The tsv object extends the tsv/2 parametric object using the default options keep and false.

Files and streams can be read into a list of rows (with each row being represented by a list of fields) or asserted using a user-defined dynamic predicate. Reading can be done by first loading the whole file (using the read_file/2-3 predicates) into memory or line by line (using the read_file_by_line/2-3 predicates). Reading line by line is usually the best option for parsing large TSV files.

Data can be saved to a TSV file or stream by providing the object and predicate for accessing the data plus the name of the destination file or the stream handle or alias.

API documentation

Open the [../../apis/library_index.html#tsv](../../apis/library_index.html#tsv) link in a web browser.

Loading

To load all entities in this library, load the loader.lgt file:

| ?- logtalk_load(tsv(loader)).

Testing

To test this library predicates, load the tester.lgt file:

| ?- logtalk_load(tsv(tester)).

Usage

A TSV file can be read as a list of rows:

| ?- tsv::read_file('test_files/data.tsv', Rows).

Rows = [['Name','Age','Address'], ['Paul',23,'1115 W Franklin'], ['Bessy the Cow',5,'Big Farm Way'], ['Zeke,45,'W Main St']] yes

Alternatively, The TSV data can be saved using a public and dynamic object predicate (that must be previously declared). For example:

| ?- assertz(p(_,_,_)), retractall(p(_,_,_)). yes

| ?- tsv(skip)::read_file('test_files/data.tsv', user, p/3). yes

| ?- tsv(skip, true)::read_file('test_files/data_with_comments.tsv', user, p/3). yes

| ?- p(A,B,C).

A = 'Paul', B = 23, C = '1115 W Franklin' ? ; ...

Given a predicate representing a table, the predicate data can be written to a file or stream. For example:

| ?- tsv::write_file('output.tsv', user, p/3). yes