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The simplest Go code that can be included on a Web is at the level of an expression. Any Go expression—including constants, variables, operators, function calls, etc.—can be used. The only restriction is that the result be convertible to a string. In other words, if the expression can serve as the argument to fmt.Sprintf("%v", …), it can appear within ?go:expr markup.

As a very simple example,

<p>One-third is approximately <?go:expr 1.0/3.0 ?>.</p>

appears to the client exactly as if the page had been written

<p>One-third is approximately 0.3333333333333333.</p>

Expressions can invoke any function that previously has been imported or defined. For example, if the fmt package has been imported,

<p>One-third is written as <?go:expr fmt.Sprintf("%e", 1.0/3.0) ?> in scientific notation.</p>


<p>One-third is written as 3.333333e-01 in scientific notation.</p>