<pre class="grammar">
Production  = production_name "=" [ Expression ] "." .
Expression  = Alternative { "|" Alternative } .
Alternative = Term { Term } .
Term        = production_name | token [ "…" token ] | Group | Option | Repetition .
Group       = "(" Expression ")" .
Option      = "[" Expression "]" .
Repetition  = "{" Expression "}" .
</pre>

<p>
Productions are expressions constructed from terms and the following

defined as the partial order requirements set out by the <a href="/ref/spec">Go language specification</a>
for Go's control flow constructs as well as the <a href="/ref/spec#Order_of_evaluation">order of evaluation for expressions</a>.
</p>

<p>
A Go <i>program execution</i> is modeled as a set of goroutine executions,
together with a mapping <i>W</i> that specifies the write-like operation that each read-like operation reads from.

Syntax      = { Production } .
Production  = production_name "=" [ Expression ] "." .
Expression  = Term { "|" Term } .
Term        = Factor { Factor } .
Factor      = production_name | token [ "…" token ] | Group | Option | Repetition .
Group       = "(" Expression ")" .
Option      = "[" Expression "]" .
Repetition  = "{" Expression "}" .
</pre>

<p>
Productions are expressions constructed from terms and the following

      function removes any enclosing
      <a href='https://pkg.go.dev/go/ast#ParenExpr'>parentheses</a> from
      an <a href='https://pkg.go.dev/go/ast#Expr'>expression</a>.
    </p>
  </dd>
</dl><!-- go/ast -->

<dl id="go/types"><dt><a href="/pkg/go/types/">go/types</a></dt>
  <dd>
    <p><!-- https://go.dev/issue/63223, CL 521956, CL 541737 -->

<h3 id="constants">Constants</h3>

<p>
Although the assembler takes its guidance from the Plan 9 assemblers,
it is a distinct program, so there are some differences.
One is in constant evaluation.
Constant expressions in the assembler are parsed using Go's operator
precedence, not the C-like precedence of the original.
Thus <code>3&amp;1&lt;&lt;2</code> is 4, not 0—it parses as <code>(3&amp;1)&lt;&lt;2</code>