Whitespace (programming language)

<h2 id="history">History</h2>
<p>Edwin Brady and Chris Morris, who also developed the Kaya and <a href="/facts/Idris_(programming_language)/lIK3b84A">Idris</a> languages, created Whitespace in 2002 at the <a href="/facts/University_of_Durham/VJHcWdkh">University of Durham</a>. 
<a href="/facts/Slashdot/vVpMuby2">Slashdot</a> published a review on <a href="/facts/April_Fool%2527s_Day/KXnQtCTX">April Fool's Day</a> 2003.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
</p><p>The idea of using whitespace characters as operators for the <a href="/facts/C%252B%252B/Et0F2qn9">C++</a> language had been facetiously suggested five years earlier by <a href="/facts/Bjarne_Stroustrup/Be1Yq6rn">Bjarne Stroustrup</a>.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a>
</p>
<h2 id="syntax">Syntax</h2>
<p>Whitespace defines a command as a sequences of whitespace characters. For example, [Tab][Space][Space][Space] performs arithmetic addition of the top two elements on the stack.
</p><p>A command is written as an instruction modification parameter (IMP) followed by an operation and then any parameters.
<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> 
</p><p>IMP sequences include:
</p>
<table><tbody><tr><th>IMP</th><th>Meaning</th></tr><tr><td>[Space]</td><td>Stack Manipulation</td></tr><tr><td>[Tab][Space]</td><td>Arithmetic</td></tr><tr><td>[Tab][Tab]</td><td>Heap Access</td></tr><tr><td>[LineFeed]</td><td>Flow Control</td></tr><tr><td>[Tab][LineFeed]</td><td>I/O</td></tr></tbody></table>
<p>Operator sequences, organized by IMP, include:<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a>
</p>
<table><tbody><tr><th>IMP</th><th>Operator</th><th>Parameter</th><th>Meaning</th><th>Minimum size of the stack required*</th></tr><tr><td>[Space]</td><td>[Space]</td><td>Number</td><td>Push the number onto the stack</td><td>0</td></tr><tr><td>[Space]</td><td>[LF][Space]</td><td>-</td><td>Duplicate the top item on the stack</td><td>1</td></tr><tr><td>[Space]</td><td>[Tab][Space]</td><td>Number <i>n</i></td><td>Copy the nth item on the stack (given by the argument) onto the top of the stack**</td><td><i>n</i>+1</td></tr><tr><td>[Space]</td><td>[LF][Tab]</td><td>-</td><td>Swap the top two items on the stack</td><td>2</td></tr><tr><td>[Space]</td><td>[LF][LF]</td><td>-</td><td>Discard the top item on the stack</td><td>1</td></tr><tr><td>[Space]</td><td>[Tab][LF]</td><td>Number <i>n</i></td><td>Slide n items off the stack, keeping the top item**</td><td>may be less than <i>n</i>+1,<p>but at least 1 item(top of the stack)is required</p></td></tr><tr><td>[Tab][Space]</td><td>[Space][Space]</td><td>-</td><td>Addition</td><td>2</td></tr><tr><td>[Tab][Space]</td><td>[Space][Tab]</td><td>-</td><td>Subtraction</td><td>2</td></tr><tr><td>[Tab][Space]</td><td>[Space][LF]</td><td>-</td><td>Multiplication</td><td>2</td></tr><tr><td>[Tab][Space]</td><td>[Tab][Space]</td><td>-</td><td>Integer division</td><td>2 (top may not be 0)</td></tr><tr><td>[Tab][Space]</td><td>[Tab][Tab]</td><td>-</td><td><a href="/facts/Modulo_operation/V5xPUluD">Modulo</a></td><td>2 (top may not be 0)</td></tr><tr><td>[Tab][Tab]</td><td>[Space]</td><td>-</td><td>Store in heap</td><td>2</td></tr><tr><td>[Tab][Tab]</td><td>[Tab]</td><td>-</td><td>Retrieve from heap</td><td>1</td></tr><tr><td>[LF]</td><td>[Space][Space]</td><td>Label</td><td>Mark a location in the program</td><td>0</td></tr><tr><td>[LF]</td><td>[Space][Tab]</td><td>Label</td><td>Call a subroutine</td><td>0</td></tr><tr><td>[LF]</td><td>[Space][LF]</td><td>Label</td><td>Jump to a label</td><td>0</td></tr><tr><td>[LF]</td><td>[Tab][Space]</td><td>Label</td><td>Jump to a label if the top of the stack is zero</td><td>1</td></tr><tr><td>[LF]</td><td>[Tab][Tab]</td><td>Label</td><td>Jump to a label if the top of the stack is negative</td><td>1</td></tr><tr><td>[LF]</td><td>[Tab][LF]</td><td>-</td><td>End a subroutine and transfer control back to the caller</td><td>0 <i>(callstack: 1)</i></td></tr><tr><td>[LF]</td><td>[LF][LF]</td><td>-</td><td>End the program</td><td>0</td></tr><tr><td>[Tab][LF]</td><td>[Space][Space]</td><td>-</td><td>Output the character at the top of the stack</td><td>1</td></tr><tr><td>[Tab][LF]</td><td>[Space][Tab]</td><td>-</td><td>Output the number at the top of the stack</td><td>1</td></tr><tr><td>[Tab][LF]</td><td>[Tab][Space]</td><td>-</td><td>Read a character and place it in the location given by the top of the stack</td><td>1</td></tr><tr><td>[Tab][LF]</td><td>[Tab][Tab]</td><td>-</td><td>Read a number and place it in the location given by the top of the stack</td><td>1</td></tr></tbody></table>
<p>*Due to Haskell being lazily evaluated, the effect of the stack being too small may only show when, for example, invoking the <i>outputting a number</i> side-effect.
</p><p>**The <i>copy</i> and <i>slide</i> operations were added in Whitespace 0.3.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a>
</p>
<h3>Comments</h3>
<p>Characters other than space, tab and linefeed are ignored and thus can be used for comments. 
</p>
<h3>Numbers</h3>
<p>A numeric value is represented as a sequence of space and tab characters that represent 0 and 1 respectively and terminated by a linefeed. The first character represents the <a href="/facts/Sign_(mathematics)/z0xollg1">sign</a> of the value – space for positive and tab for negative. Subsequent characters before the terminator represent the binary digits of a value.
</p><p>For example:
</p>
<ul><li>[space][tab][space][space][tab][space][tab][tab][linefeed] (STSSTSTTL) is positive since it starts with space and represents 1001011 in binary, which is 75 in decimal.</li>
<li>[tab][tab][tab][space][space][tab][space][linefeed] (TTTSSTSL) is negative since it starts with tab and represents -110010 in binary which is −50 in decimal.</li></ul>
<h3>Labels</h3>
<p>A label is used for <a href="/facts/Control_flow/2XTDfErC">control flow</a>. It is a linefeed-terminated sequence of spaceand tab characters. As there is only one namespace, all labels must be unique.
<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a>
</p>
<h2 id="sample-code">Sample code</h2>
<p>The following source code is for a Whitespace <a href="/facts/Hello_world_program/vLn0jLlL">"Hello, world!"</a> program. For clarity, it is annotated with S, T and L before each
space,
tab, and linefeed.
</p>
S S S T	S S T	S S S L:Push_+1001000=72='H'_onto_the_stack
T	L
S S :Output_'H';_S S S T	T	S S T	S T	L:Push_+1100101=101='e'_onto_the_stack
T	L
S S :Output_'e';_S S S T	T	S T	T	S S L:+1101100=108='l'
T	L
S S S S S T	T	S T	T	S S L:+1101100=108='l'
T	L
S S S S S T	T	S T	T	T	T	L:+1101111=111='o'
T	L
S S S S S T	S T	T	S S L:+101100=44=','
T	L
S S S S S T	S S S S S L:+100000=32=Space
T	L
S S S S S T	T	T	S T	T	T	L:+1110111=119='w'
T	L
S S S S S T	T	S T	T	T	T	L:+1101111=111='o'
T	L
S S S S S T	T	T	S S T	S L:+1110010=114='r'
T	L
S S S S S T	T	S T	T	S S L:+1101100=108='l'
T	L
S S S S S T	T	S S T	S S L=+1100100=100='d'
T	L
S S S S S T	S S S S T	L:+100001=33='!'
T	L
S S :Output_'!';_L
L
L:End_the_program

<p>When Whitespace source code is displayed in some browsers, the horizontal spacing produced by a tab character is not fixed, but depends on its location in the text relative to the next <a href="/facts/Tab_key/gTyIhqBe">horizontal tab stop</a>. Depending on the software, tab characters may also get replaced by the corresponding variable number of space characters.
</p>

<h2 id="external-links">External links</h2>
<ul><li><a href="https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php">Official website</a></li>
<li><a href="http://developers.slashdot.org/article.pl?sid=03/04/01/0332202">Release announcement on Slashdot</a></li>
<li><a href="https://github.com/wspace/corpus">The Whitespace Corpus</a> A collection of interpreters, compilers, and programs for Whitespace</li>
<li><a href="https://github.com/hostilefork/whitespacers/">Collection of Whitespace interpreters in various script languages</a></li>
<li><a href="http://metacpan.org/module/Acme::Bleach">Acme::Bleach</a> A <a href="/facts/Perl/fx31kjlT">Perl</a> module that rewrites the body of your module to a whitespace-only encoding ("for <i>really</i> clean programs").</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"Whitespace". Compsoc. Archived from the original on 18 June 2015. Retrieved 8 December 2015. <a href="https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php" target="_blank">https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Parker, Matt (2019). Humble Pi: a comedy of maths errors. Allen Lane. p. 21. ISBN 978-0-241-36023-1. <a href="978-0-241-36023-1" target="_blank">978-0-241-36023-1</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Parker, Matt (2019). Humble Pi: a comedy of maths errors. Allen Lane. p. 21. ISBN 978-0-241-36023-1. <a href="978-0-241-36023-1" target="_blank">978-0-241-36023-1</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Timothy (1 April 2003). "New Whitespace-Only Programming Language". Slashdot. Retrieved 23 January 2014. <a href="http://developers.slashdot.org/story/03/04/01/0332202/New-Whitespace-Only-Programming-Language" target="_blank">http://developers.slashdot.org/story/03/04/01/0332202/New-Whitespace-Only-Programming-Language</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Stroustrup, Bjarne. "Generalizing Overloading for C++2000" (PDF). Florham Park, NJ, USA: AT&T Labs. Retrieved 23 January 2014. <a href="http://www.stroustrup.com/whitespace98.pdf" target="_blank">http://www.stroustrup.com/whitespace98.pdf</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>"Whitespace". Compsoc. Archived from the original on 18 June 2015. Retrieved 8 December 2015. <a href="https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php" target="_blank">https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>"Whitespace". Compsoc. Archived from the original on 18 June 2015. Retrieved 8 December 2015. <a href="https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php" target="_blank">https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>"Whitespace". Compsoc. Archived from the original on 18 June 2015. Retrieved 8 December 2015. <a href="https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php" target="_blank">https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
<li id="fn:9"><p>"Whitespace". Compsoc. Archived from the original on 18 June 2015. Retrieved 8 December 2015. <a href="https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php" target="_blank">https://web.archive.org/web/20150618184706/http://compsoc.dur.ac.uk/whitespace/tutorial.php</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li>
</ol>

Whitespace (programming language) open-in-new

Whitespace (programming language)