在模拟NS2中无线传感器网络的路由协议时，从a函数内部访问节点会产生错误“没有这样的变量”。

Question

我正在尝试编写60个节点和1个移动水槽的代码，其中18个节点充当高层节点或骨干节点。移动水槽会定期更新位置，以便只有骨干节点和其他节点可以在需要时查询水槽位置。

#node creation
#Node 1 to 18 are backbone nodes
#nodes 19 to 59 are normal sensor nodes
#node 60 is the mobile sink
    set node_(0) [$ns node]
    set node_(1) [$ns node]
    .
    .
    .
#node no 60 is the mobile sink..
    set node_(60) [$ns node]

    
    #node X Y coordinate initialized
    $node_(0) set X_ 2
    $node_(0) set Y_ 3
    $node_(1) set X_ 517
    $node_(1) set Y_ 299
    .
    .
    $node_(63) set  X_ 306
    $node_(63) set  Y_ 178
    
    proc distBN {n1 n2 nid1 nid2} {
        set x1 [expr int([$n1 set X_])]
        set y1 [expr int([$n1 set Y_])]
        set x2 [expr int([$n2 set X_])]
        set y2 [expr int([$n2 set Y_])]
        set d [expr int(sqrt(pow(($x2-$x1),2)+pow(($y2-$y1),2)))]
        #checking that it is in the transmission range i.e 100m
        if {$d<100} {
            if {$nid2!=$nid1} {
                return $d;
            }            
        }
    }
    
    
    #This function starts the transmission of Mobile Sink location every 5 seconds 
    proc locTrans {} {
        global ns
        set dist_min 101
        set dist 101
        set sink_loc 60
        puts "[$ns now] : Finding the nearest backbone node to sink node $sink_loc..."
        for {set j 0} {$j < 19} {incr j} {
            set dist [expr "distBN $node_($sink_loc) $node_($j) $sink_loc $j"]; ## <<< THIS LINE
            puts "Distance between sink and node $j is $dist...\n"
            if{$dist_min > $dist} {
                set dist_min $dist 
            }
            puts "Running loop for $j time...\n"
        }
        puts "The smallest distance is $dist_min between node_(60) and node_($j)\n"
        puts "[$ns now] : transmitting sink location to nearest backbone node...\n"
        $ns at [expr [$ns now] + 3.0] "locTrans"  
    }

过程loctrans（）调用另一个函数distbn（）来计算参数中传递的节点之间的距离。但是运行代码会产生以下错误：

> ns: locTrans: can't read "node_(60)": no such variable
    while executing
"expr "distBN $node_($sink_loc) $node_($j) $sink_loc $j""
    (procedure "locTrans" line 9)
    invoked from within
"locTrans"

错误屏幕快照

Answer 1

问题在于，整体节点_数组不在过程中的范围（因为TCL仅在明确要求它们的情况下可以提供非本地变量）。幸运的是，修复很容易：更新全局ns命令上面几行，

global ns node_

---

请注意，您的代码中有几个错误：您不处理测量距离的情况从一个节点到自身（现在，您有效地返回空字符串; i bet 您都不想要！），您已经写了电话distbn错误，应该这样做：

set dist [distBN $node_($sink_loc) $node_($j) $sink_loc $j]

您写的是...不去工作。