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copied!<blockquote> <p>[Does anybody know] other grammar "peculiarities" of modern programming languages?</p> </blockquote> <p>One of my favorites, <a href="http://www.modula3.org" rel="nofollow noreferrer">Modula-3</a>, was designed in 1990 with Niklaus Wirth's blessing as the then-latest language in the "Pascal family". Does anyone else remember those <strong>awful fights about where semicolon should be a <em>separator</em> or a <em>terminator</em>?</strong> In Modula-3, the choice is yours! The EBNF for a sequence of statements is</p> <pre><code>stmt ::= BEGIN [stmt {; stmt} [;]] END </code></pre> <p>Similarly, when writing alternatives in a <code>CASE</code> statement, Modula-3 let you use the vertical bar <code>|</code> as either a separator or a prefix. So you could write</p> <pre><code>CASE c OF | 'a', 'e', 'i', 'o', 'u' => RETURN Char.Vowel | 'y' => RETURN Char.Semivowel ELSE RETURN Char.Consonant END </code></pre> <p>or you could leave off the initial bar, perhaps because you prefer to write <code>OF</code> in that position.</p> <p>I think what I liked as much as the design itself was the designers' awareness that there was a religious war going on and their persistence in finding a way to support both sides. Let the programmer choose!</p> <hr> <p>P.S. Objective Caml allows permissive use of <code>|</code> in case expressions whereas the earlier and closely related dialect Standard ML does not. As a result, case expressions are often uglier in Standard ML code.</p> <hr> <p><strong>EDIT</strong>: After seeing T.E.D.'s answer I checked the Modula-2 grammar and he's correct, Modula-2 also supported semicolon as terminator, but through the device of the empty statement, which makes stuff like </p> <pre><code>x := x + 1;;;;;; RETURN x </code></pre> <p>legal. I suppose that's not a bad thing. Modula-2 didn't allow flexible use of the case separator <code>|</code>, however; that seems to have originated with Modula-3.</p>

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