user-defined iterators.

The [slices] package adds several functions that work with iterators:
- [All](/pkg/slices#All) returns an iterator over slice indexes and values.
- [Values](/pkg/slices#Values) returns an iterator over slice elements.
- [Backward](/pkg/slices#Backward) returns an iterator that loops over
  a slice backward.
- [Collect](/pkg/slices#Collect) collects values from an iterator into
  a new slice.

	// Retrieve the size of the shared memory to enable slice creation
	var info SysvShmDesc

	_, err := SysvShmCtl(id, IPC_STAT, &info)
	if err != nil {
		// release the shared memory if we can't find the size

		// ignoring error from shmdt as there's nothing sensible to return here
		shmdt(addr)
		return nil, err
	}

	// Use unsafe to convert addr into a []byte.
	b := unsafe.Slice((*byte)(unsafe.Pointer(addr)), int(info.Segsz))

	i := c.Index()
	if i < 0 {
		panic("Delete node not contained in slice")
	}
	v := c.field()
	l := v.Len()
	reflect.Copy(v.Slice(i, l), v.Slice(i+1, l))
	v.Index(l - 1).Set(reflect.Zero(v.Type().Elem()))
	v.SetLen(l - 1)
	c.iter.step--
}

// InsertAfter inserts n after the current Node in its containing slice.
// If the current Node is not part of a slice, InsertAfter panics.
// Apply does not walk n.

	nif.Cond = ir.NewBinaryExpr(base.Pos, ir.OLE, nuint, scapuint)
	nif.Likely = true

	// then { s = s[:newLen] }
	slice := ir.NewSliceExpr(base.Pos, ir.OSLICE, s, nil, newLen, nil)
	slice.SetBounded(true)
	nif.Body = []ir.Node{ir.NewAssignStmt(base.Pos, s, slice)}

	// else { s = growslice(oldPtr, newLen, oldCap, num, T) }
	call := walkGrowslice(s, nif.PtrInit(), oldPtr, newLen, oldCap, num)

}

func (g *gcmAsm) Overhead() int {
	return g.tagSize
}

// sliceForAppend takes a slice and a requested number of bytes. It returns a
// slice with the contents of the given slice followed by that many bytes and a
// second slice that aliases into it and contains only the extra bytes. If the
// original slice has sufficient capacity then no allocation is performed.
func sliceForAppend(in []byte, n int) (head, tail []byte) {

		panic("non-executing goroutine stopped")
	}
	ctx.Slice(traceviewer.SliceEvent{
		Name:     gs.name(),
		Ts:       ctx.elapsed(gs.startRunningTime),
		Dur:      ts.Sub(gs.startRunningTime),
		Resource: uint64(gs.executing),
		Stack:    stk,
	})

	// Flush completed ranges.
	for _, cr := range gs.completedRanges {
		ctx.Slice(traceviewer.SliceEvent{
			Name:     cr.name,

// creating Coverage implementations for partially defined data. Very often a
// package will only need to define a subset of slices. coverage provides a
// convenient way to do this. Moreover, packages using NewCoverage, instead of
// their own implementation, will not break if later new slice types are added.
type coverage struct {
	tags    func() []Tag
	bases   func() []Base
	scripts func() []Script
	regions func() []Region
}

	//  var i string
	//  var _ = s[i]
	InvalidIndex

	// SwappedSliceIndices occurs when constant indices in a slice expression
	// are decreasing in value.
	//
	// Example:
	//  var _ = []int{1,2,3}[2:1]
	SwappedSliceIndices

	/* operators > slice */

	// NonSliceableOperand occurs when a slice operation is applied to a value
	// whose type is not sliceable, or is unaddressable.
	//
	// Example:

The <i>capacity</i> is a measure of that extent: it is the sum of
the length of the slice and the length of the array beyond the slice;
a slice of length up to that capacity can be created by
<a href="#Slice_expressions"><i>slicing</i></a> a new one from the original slice.
The capacity of a slice <code>a</code> can be discovered using the
built-in function <a href="#Length_and_capacity"><code>cap(a)</code></a>.
</p>

	// of nodes to use when the tree is being constructed.
	nodes    []huffmanNode
	nextNode int
}

// A huffmanNode is a node in the tree. left and right contain indexes into the
// nodes slice of the tree. If left or right is invalidNodeValue then the child
// is a left node and its value is in leftValue/rightValue.
//
// The symbols are uint16s because bzip2 encodes not only MTF indexes in the