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copied!<p>I'm not sure what the convention is for using <code>_!</code> and <code>_!!</code> in Lift, but here's a bit of background.</p> <p>Any alphanumeric identifier can have _ and a list of symbols added and still be parsed as a single identifier. For example:</p> <pre><code>scala> class Example_!@%*! defined class Example_$bang$at$percent$times$bang </code></pre> <p>(In fact, you can parse almost anything as an identifier if you surround it with backticks--and this is what you do if a Java class uses a Scala reserved word, for example. Or if you want spaces in your identifiers.)</p> <p>The compiler only recognizes one symbolic ending specially, however. If there is a method that looks like a getter, then getter_= will be interpreted as a setter. (Whether you actually <em>use</em> it as a setter is up to you; it will have the semantics of a setter, anyway.) So</p> <pre><code>scala> class Q { def q = "Hi"; def q_=(s: String) { println(s.reverse) } } defined class Q scala> val q = new Q q: Q = Q@b5c12e scala> q.q res0: java.lang.String = Hi scala> q.q = "Could use this to set something" gnihtemos tes ot siht esu dluoC </code></pre> <p>In addition, the compiler reverses the order of caller and callee in <em>any</em> method that ends in <code>:</code>. This is most often seen in lists: <code>newElement :: existingList</code> is actually a call to <code>existingList.::(newElement)</code>. So, for example:</p> <pre><code>scala> object Caps { def to_:(s: String) = s.toUpperCase } defined module Caps scala> "Example" to_: Caps res40: java.lang.String = EXAMPLE </code></pre> <p>Any other usage of <code>_</code> + symbols is convention.</p>

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