FAUST (programming language): Difference between revisions

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{{Short description|Audio programming language}}

{{No footnotes|date=March 2015}}

{{redirect|FAUST|other uses|Faust (disambiguation){{!}}Faust}}

{{NoMore footnotes needed|date=March 2015}}

{{Infobox software

| name = FAUST

| developer = GRAME, Centre National de Création Musicale

| author = Yann Orlarey, Dominique Fober, Stéphane Letz

| released = {{releasestart date|2002}}

| latest release version = 02.960.673<ref>[https://github.com/grame-cncm/faust/releases Releases · grame-cncm/faust · GitHub]</ref>

| latest release date = {{releasestart date|20142023|0506|1914}}

| operating system = [[Linux]], [[OS X]], [[Microsoft Windows|Windows]], [[Unix]]

| genre = Functional programming language for audio signal processing

| repo = {{URL|https://github.com/grame-cncm/faust/}}

| programming language = [[C++]]

| license = [[GNU General Public License|GPL]]

| website = {{URL|faust.grame.fr}}

}}

{{Portal|Free and open-source software}}

'''FAUST''' (Functional AUdio STream) is a [[Domain ___domain-specific language|___domain-specific]] [[Purelypurely functional programming|purely functional]] [[programming language]] for implementing [[signal processing]] [[algorithms]] in the form of [[Library (computing)|libraries]], [[audio plug-ins]], or standalone applications. A FAUST program denotes a signal processor: a mathematical function that is applied to some input signal and then fed out.

==Overview==

The FAUST [[programming model]] combines a [[functional programming]] approach with a [[block diagram]] syntax:

* The functional programming approach provides a natural framework for [[signal processing]]. Digital signals are modeled as [[Sequence|discrete functions]] of time, signal processors as [[Higher-order function|second order functions]] that operate on them, and FAUST’sFAUST's block diagram ''composition operators'', used to combine signal processors together, as third order functions, etc.

* Block diagrams, even if purely textual as in FAUST, promote a modular approach to signal processing that complies with sound engineers' and audio developers' habits.

A FAUST program doesn’tdoesn't describe a sound or a group of sounds, but a [[Digital signal processing|signal processor]]. The program source is organized as a set of ''definitions'' with at least the definition of the keyword <code>process</code> (the equivalent of <code>main</code> in C):

<sourcesyntaxhighlight lang=haskell>

process = ...;

</syntaxhighlight>

</source>

The FAUST [[compiler]] translates FAUST code into a [[C++]] [[Object-oriented programming|object]], which may then interface with other C++ code to produce a full program.

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==Example code==

FAUST programs define a <code>process</code> function that operates on incoming data. This is analogous to the <code>main</code> function in most programming languages. The following is an example that produces silence:

<sourcesyntaxhighlight lang="haskell">

process = 0;

</syntaxhighlight>

</source>

The second example copies the input signal to the output. It involves the <code>_</code> primitive that denotes the [[identity function]] for signals:

<sourcesyntaxhighlight lang="haskell">

process = _;

</syntaxhighlight>

</source>

Another example sums a stereo signal into a mono signal using the <code>+</code> primitive:

<sourcesyntaxhighlight lang="haskell">

process = +;

</syntaxhighlight>

</source>

[[File:Faust-simple-block-diagram.jpg|thumb|Block diagrams generated by Faust from some simple programs]]

Most FAUST primitives are analogous to their C counterpart on numbers, but lifted to signals. For example, the FAUST primitive <code>sin</code> operates on a signal X by applying the [[C (programming language)|C]] function <code>sin</code> to each sample X[t]. All C numerical functions have their counterpart in FAUST.

Some [[signal processing]] primitives are specific to FAUST. For example, the delay operator <code>@</code> takes two input signals: X (the signal to be delayed) and D (the delay to be applied), and produces an output signal Y such that Y(t) = X(t − D(t)).

==Block diagram composition==

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Using the sequential composition operator <code>:</code> the output of <code>+</code> can be routed to the input of <code>abs</code> to compute the [[absolute value]] of the signal:

<sourcesyntaxhighlight lang="haskell">

process = + : abs;

</syntaxhighlight>

</source>

Here is an example of parallel composition using the <code>,</code> operator that arranges its left and right expressions in parallel. This is analogous to a stereo cable.

<sourcesyntaxhighlight lang="haskell">

process = _,_;

</syntaxhighlight>

</source>

These operators can be arbitrarily combined arbitrarily. The following code multiplies an input signal with 0.5:

<sourcesyntaxhighlight lang="haskell">

process = _,0.5 : *;

</syntaxhighlight>

</source>

The above may be rewritten in [[currying|curried]] form:

<sourcesyntaxhighlight lang="haskell">

process = *(0.5);

</syntaxhighlight>

</source>

The recursive composition operator <code>~</code> can be used to create block diagrams with cycles (that include an implicit one-sample delay). Here is an example of an integrator that takes an input signal X and computes an output signal Y such that Y(t) = X(t) + Y(t−1):

<sourcesyntaxhighlight lang=haskell>

process = + ~ _;

</syntaxhighlight>

</source>

==Generating full applications==

Using specific ''architecture files'', a FAUST program can be used to produce code for a variety of platforms and plug-in formats. These architecture files act as wrappers and describe the interactions with the host audio and GUI system. {{As of|20152021}}, more than 1030 architectures are supported and new ones may be implemented by anyone.

[[File:Faust-mixer-jackqt.jpg|thumb|Screenshot of mixer.dsp (available in the FAUST distribution) using the jack-qt architecture]]

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{| class="wikitable"

|+ Some architecture files available for FAUST

! File

| alsa-gtk.cpp || ALSA application + GTK

! Architecture

|-

| alsa-qtgtk.cpp || ALSA application + QT4[[GTK]]

|-

| alsa-gtkqt.cpp || ALSA application + GTK[[Qt (software)|Qt]] 4

|-

| android.cpp || Android applications

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| au.cpp || Audio Unit plug-in

|-

| ca-qt.cpp || CoreAudio application + QT4Qt 4

|-

| ios-coreaudio.cpp || iPhone and iPad applications

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| jack-gtk.cpp || JACK application + GTK

|-

| jack-qt.cpp || JACK application + QT4Qt 4

|-

| ladspa.cpp || LADSPA plug-in

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| max-msp.cpp || Max MSP plug-in

|-

| pd.cpp || PuredataPure Data plug-in

|-

| q.cpp || Q language plug-in

|-

| supercollider.cpp || SupercolliderSuperCollider plug-in

|-

| vst.cpp || VST plug-in

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A useful option makes it possible to generate the block diagram representation of the program as one or more SVG graphic files.

It is useful to note the difference between the block diagram and the generated C++ code. As stated, the key idea here is not to compile the block diagram literally, but the mathematical function it denotes. Modern C/C++ compilers also don’tdon't compile programs literally. But because of the complex semantics of C/C++ (due to side effects, pointer aliasing, etc.) they can’tcan't go very far in that direction. This is a distinct advantage of a purely functional language: it allows compilers to do very advanced optimisations.

==Arrows-like semantics==

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{| class="wikitable"

|+ Equivalences between FAUST and Arrow combinators

| <code>f~g</code> || <{{code>|2=haskell|1=loop ((\(a,b) -> (b,a)) ^>> f >>> id &&& (delay>>>g))</code>}} where <code>delay</code> is not a method of the <code>Arrow</code> type class, but is specific to signal processing arrows

|-

| <code>f,g</code> || <code>f***g</code>

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| year = 2011

}}

* {{cite journal

|first1 =Pierre Pierre

|last1 =Jouvelot Jouvelot

|first2 =Yann Yann

|last2 =Orlarey Orlarey

|title = Dependent Vector Types for Data Structuring in Multirate Faust

|journal = Computer Languages, Systems and& Structures&nbsp;– Elsevier

|url = http://faust.grame.fr/images/faust-doc/papers/faust-elsevier2011.pdf

|year =2011 2011

|volume=37

}}

|issue=3

|pages=113–131

|doi=10.1016/j.cl.2011.03.001

}}{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }}

* {{Cite web

| first = Julius O.

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| year = 2011

}}

* {{cite journal

| first3 =Dominique Dominique

| last3 =Fober Fober

| first1 =Yann Yann

| last1 =Orlarey Orlarey

| first2 =Stéphane Stéphane

| last2 =Letz Letz

| title = Automatic Parallelization of Audio Applications with Faust

| journal = Proceedings of the Congrès Français d'Acoustique

| url = http://faust.grame.fr/images/faust-doc/papers/faust-CFA-2010.pdf

| year =2010 2010

}}{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

* {{cite journal

| first3 = Dominique

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| year = 2010

}}

* {{cite journal

| first1 =Jérôme Jérôme

| last1 =Barthélemy Barthélemy

| first2 =Alain Alain

| last2 =Bonardi Bonardi

| first3 =Yann Yann

| last3 =Orlarey Orlarey

| first4 =Serge Serge

| last4 =Lemouton Lemouton

| first5 =Raffaele Raffaele

| last5 =Ciavarella Ciavarella

| first6 =Karim Karim

| last6 =Barkati Barkati

| title = First Steps Towards an Organology of Virtual Instruments in Computer Music

| journal = Proceedings of the 2010 International Computer Music Conference (ICMA-2010)

| url = http://faust.grame.fr/images/faust-doc/papers/astree-icmc2010.pdf

| pages =369–372 369–372

| year =2010 2010

}}{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

* {{cite journal

| first1 = Pierre

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| last2 = Orlarey

| title = Depandant Vector Types for Multirate Faust

| journal = Proceedings of the 7th Sound anand Music Computing Conference (SMC-2010)

| url = http://smcnetwork.org/files/proceedings/2010/51.pdf

| pages = 345–352

| year = 2010

| access-date = 2011-10-11

| archive-url = https://web.archive.org/web/20120407043121/http://smcnetwork.org/files/proceedings/2010/51.pdf

| archive-date = 2012-04-07

| url-status = dead

}}

* {{cite journal

| first3 =Dominique Dominique

| last3 =Fober Fober

| first1 =Yann Yann

| last1 =Orlarey Orlarey

| first2 =Stéphane Stéphane

| last2 =Letz Letz

| title = Adding Automatic Parallelization to Faust

| journal = Proceedings of the Linux Audio Conference (LAC-2009)

| url = http://faust.grame.fr/test/images/faust-doc/papers/faustLAC09.pdf

| year =2009 2009

}}{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

* {{cite book

| first1 = Pierre

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| url = http://faust.grame.fr/images/faust-doc/papers/multirate-faust.pdf

| year = 2009

}}{{Dead link|date=December 2019 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

* {{cite journal

| first2 = Dominique

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| url = http://smc2009.smcnetwork.org/programme/pdfs/232.pdf

| year = 2009

| archive-date = 2012-04-25

| access-date = 2011-10-11

| archive-url = https://web.archive.org/web/20120425061241/http://smc2009.smcnetwork.org/programme/pdfs/232.pdf

| url-status = dead

}}

* {{cite book

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| isbn = 978-2-7521-0054-2

| year = 2009

}}{{Dead link|date=December 2019 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

* {{cite journal

| first3 =Dominique Dominique

| last3 =Fober Fober

| first1 =Yann Yann

| last1 =Orlarey Orlarey

| first2 =Stéphane Stéphane

| last2 =Letz Letz

| title = Multicore Technologies in Jack and Faust

| journal = Proceedings of the 2010 International Computer Music Conference (ICMC-2008)

| url = http://faust.grame.fr/images/faust-doc/papers/jack-faust-multicore.pdf

| year =2008 2008

}}{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

* {{cite journal

| first = Albert

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| last = Smith III

| title = Introduction to Digital Filters: With Audio Applications

| chapter = Appendix K. Digital Filtering in Faust and PD

| publisher = W3K Publishing

| year = 2007

| isbn = 978-0-9745607-1-7

| chapter-url = https://books.google.com/books?id=pC1iCQUAsHEC&pg=PA417

| pages = 417-417–?

}}

* {{cite journal

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| publisher = Computer Music Association

| url = http://quod.lib.umich.edu/cgi/t/text/text-idx?c=icmc;idno=bbp2372.2005.*

| chapterurlchapter-url = http://quod.lib.umich.edu/i/icmc/bbp2372.2005.054?view=image

| year = 2005

| page = 286

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| url = http://faust.grame.fr/images/faust-doc/papers/faust-soft-computing.pdf

| year = 2004

}}{{Dead link|date=December 2019 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

* {{cite journal

| first1 =Nicolas Nicolas

| last1 =Scaringella Scaringella

| first3 =Dominique Dominique

| last3 =Fober Fober

| first2 =Yann Yann

| last2 =Orlarey Orlarey

| title = Automatic Vectorization in Faust

| journal = Journée de l'Informatique Musicale (JIM-2003)

| url = http://faust.grame.fr/images/faust-doc/papers/JIM2003vect.pdf

| year =2003 2003

}}{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

* {{cite journal

| first3 =Stéphane Stéphane

| last3 =Letz Letz

| first2 =Dominique Dominique

| last2 =Fober Fober

| first1 =Yann Yann

| last1 =Orlarey Orlarey

| title = An Algebraic Approach to Block Diagram Constructions

| journal = Journée de l'Informatique Musicale (JIM-2002)

| url = http://faust.grame.fr/images/faust-doc/papers/faust-jim2002.pdf

| year =2002 2002

}}{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

* {{cite journal

| first3 =Stéphane Stéphane

| last3 =Letz Letz

| first2 =Dominique Dominique

| last2 =Fober Fober

| first1 =Yann Yann

| last1 =Orlarey Orlarey

| title = An Algebra for Block Diagram Languages

| journal = Proceedings of International Computer Music Conference (ICMA-2002)

| url = http://faust.grame.fr/images/faust-doc/papers/faust-icmc2002.pdf

| year =2002 2002

}}{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }}

}}

{{Refend}}

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{{Commons category|FAUST (programming language)}}

* {{Official website|faust.grame.fr}}, online compiler, support, documentation, news, etc.

* {{GitHub|grame-cncm/faust}}

* [https://sourceforge.net/projects/faudiostream/ FAUST on SourceForge]: Faust repository and mailing lists

[[Category:Audio programming languages]]

[[Category:Programming languages created in 2002]]