func (c *prefixCond) Eval(s *State, suffix string) (bool, error) {
	return c.eval(s, suffix)
}

// BoolCondition returns a Cond with the given truth value and summary.
// The Cond rejects the use of condition suffixes.
func BoolCondition(summary string, v bool) Cond {
	return &boolCond{v: v, usage: CondUsage{Summary: summary}}
}

type boolCond struct {
	v     bool

func DefaultConds() map[string]script.Cond {
	conds := script.DefaultConds()
	conds["exec"] = CachedExec()
	conds["short"] = script.BoolCondition("testing.Short()", testing.Short())
	conds["verbose"] = script.BoolCondition("testing.Verbose()", testing.Verbose())
	return conds
}

// Run runs the script from the given filename starting at the given initial state.

	add("cc", script.PrefixCondition("go env CC = <suffix> (ignoring the go/env file)", ccIs))
	add("cgo", script.BoolCondition("host CGO_ENABLED", testenv.HasCGO()))
	add("cgolinkext", script.Condition("platform requires external linking for cgo", cgoLinkExt))
	add("cross", script.BoolCondition("cmd/go GOOS/GOARCH != GOHOSTOS/GOHOSTARCH", goHostOS != runtime.GOOS || goHostArch != runtime.GOARCH))