<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

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

		p.errorf("expected g or R0 through R15; found %s", name)
		return 0
	}
	return uint16(reg)
}

// Note: There are two changes in the expression handling here
// compared to the old yacc/C implementations. Neither has
// much practical consequence because the expressions we
// see in assembly code are simple, but for the record:
//
// 1) Evaluation uses uint64; the old one used int64.

To allow additional flags, set CGO_CFLAGS_ALLOW to a regular expression
matching the new flags. To disallow flags that would otherwise be allowed,
set CGO_CFLAGS_DISALLOW to a regular expression matching arguments
that must be disallowed. In both cases the regular expression must match
a full argument: to allow -mfoo=bar, use CGO_CFLAGS_ALLOW='-mfoo.*',

		}
	}
}

type astContext int

const (
	ctxProg astContext = iota
	ctxEmbedType
	ctxType
	ctxStmt
	ctxExpr
	ctxField
	ctxParam
	ctxAssign2 // assignment of a single expression to two variables
	ctxSwitch
	ctxTypeSwitch
	ctxFile
	ctxDecl
	ctxSpec
	ctxDefer
	ctxCall  // any function call other than ctxCall2
	ctxCall2 // function call whose result is assigned to two variables

//	String: the number of bytes in v.
//	Channel: the number of elements queued (unread) in the channel buffer;
//	         if v is nil, len(v) is zero.
//
// For some arguments, such as a string literal or a simple array expression, the
// result can be a constant. See the Go language specification's "Length and
// capacity" section for details.
func len(v Type) int

// The cap built-in function returns the capacity of v, according to its type:

pkg regexp/syntax, const ErrMissingParen = "missing closing )"
pkg regexp/syntax, const ErrMissingRepeatArgument = "missing argument to repetition operator"
pkg regexp/syntax, const ErrTrailingBackslash = "trailing backslash at end of expression"
pkg regexp/syntax, const ErrUnexpectedParen = "unexpected )"
pkg regexp/syntax, const ErrUnexpectedParen ErrorCode
pkg regexp/syntax, const FoldCase = 1
pkg regexp/syntax, const InstAlt = 0

pkg os/exec, method (*Cmd) Environ() []string #50599
pkg os/exec, type Cmd struct, Err error #43724
pkg os/exec, var ErrDot error #43724
pkg regexp/syntax, const ErrNestingDepth = "expression nests too deeply" #51684
pkg regexp/syntax, const ErrNestingDepth ErrorCode #51684
pkg runtime/debug, func SetMemoryLimit(int64) int64 #48409
pkg sort, func Find(int, func(int) int) (int, bool) #50340

<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>

		}
	}

	// Remove functions only used as expressions, so their respective
	// bridge functions are not generated.
	for name, used := range functions {
		if !used {
			delete(f.Name, name)
		}
	}
}

// rewriteName returns the expression used to rewrite a reference.
// If addPosition is true, add position info in the ident name.