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      <title>Curly-infix-expressions</title>
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      <h1>SRFI 105: Curly-infix-expressions</h1>
      <p class="authors">by David A. Wheeler and Alan Manuel K. Gloria</p>
      <p class="based-on"></p>
      <p class="status">status: <em>final</em> (2012-11-06)</p>
      <p class="keywords">keywords: <a href="https://srfi.schemers.org/?keywords=reader-syntax">Reader Syntax</a></p><span class="see-also">See also <a href="/srfi-266/">SRFI 266: The expr syntax</a>.</span>
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      <h2>Abstract</h2>      <p>Lisp-based languages, like Scheme, are almost       the only programming languages in modern use that do not support infix       notation. In addition, most languages allow infix expressions to be       combined with function call notation of the form       <code><var>f</var>(<var>x</var>)</code>. This SRFI provides these       capabilities, both for developers who already use Scheme and want these       conveniences, and also for other developers who may choose to use other       languages in part because they miss these conveniences. Scheme currently       reserves <code>{</code>...<code>}</code> “for possible future extensions       to the language”. We propose that <code>{</code>...<code>}</code> be used       to support “curly-infix-expression” notation as a homoiconic infix       abbreviation, as a modification of the Scheme reader. It is an       abbreviation in much the same way that <samp>'x</samp> is an abbreviation       for <samp>(quote&nbsp;x)</samp>.       <p>A <dfn>curly-infix list</dfn> introduces a list       whose visual presentation can be in infix order instead of prefix order.       For example, <samp>{n&nbsp;&gt;&nbsp;5}</samp> ⇒       <samp>(&gt;&nbsp;n&nbsp;5)</samp>, and       <samp>{a&nbsp;+&nbsp;b&nbsp;+&nbsp;c}</samp> ⇒       <samp>(+&nbsp;a&nbsp;b&nbsp;c)</samp>. By intent, there is no precedence,       but e.g., <samp>{x&nbsp;+&nbsp;{y&nbsp;*&nbsp;z}}</samp> maps cleanly to       <samp>(+&nbsp;x&nbsp;(*&nbsp;y&nbsp;z))</samp>. Forms with mixed infix       operators and other complications have “<code>$nfx$</code>” prepended to       enable later processing, e.g.,       <samp>{4&nbsp;+&nbsp;5&nbsp;*&nbsp;6}</samp> ⇒       <samp>($nfx$&nbsp;4&nbsp;+&nbsp;5&nbsp;*&nbsp;6)</samp>. Also, inside a       curly-infix list (recursively), expressions of the form       <code><var>f</var>(</code>...<code>)</code> are simply an abbreviation       for <code>(<var>f</var>&nbsp;</code>...<code>)</code>.       <p>Note that this is derived from the “<a href="http://readable.sourceforge.net/">readable</a>” project. We intend to       later submit at least one additional SRFI that will build on top of this       SRFI, but curly-infix-expressions are useful on their own.</body></html>