我用了一段时间来提取向量的tcl脚本突然停止工作,我不确定为什么。此外,错误似乎也没有意义。
我正在运行的代码是:
for {set resd 501} {$resd < 502} {incr resd 1} {
set basefile1 "CCvector$resd"
set workdir [pwd]
set nf [molinfo top get numframes]
set fil [open $basefile1.dat w]
for {set frame 0} {$frame < $nf} {incr frame 1} {
animate goto $frame
display update ui
set c1 [atomselect top "name C1 and resid $resd and resname G130"]
set c3 [atomselect top "name C3 and resid $resd and resname G130"]
set c1c [$c1 get {x y z} ]
set c3c [$c3 get {x y z} ]
set c1c3x [expr [$c3 get x]-[$c1 get x]]
set c1c3y [expr [$c3 get y]-[$c1 get y]]
set c1c3z [expr [$c3 get z]-[$c1 get z]]
set st [expr $frame]
puts $fil [list $st $c1c3x $c1c3y $c1c3z ]
$c3 delete
$c1 delete
}
close $fil
我收到的原始错误是“在 @ 上缺少操作数”,但是我将部分代码替换为:
for {set frame 0} {$frame < $nf} {incr frame 1} {
animate goto $frame
display update ui
set c1 [atomselect top "name C1 and resid $resd and resname G130"]
set c3 [atomselect top "name C3 and resid $resd and resname G130"]
set c1x [$c1 get x]
set c3x [$c3 get x]
set c1c3x [expr [$c3x - $c1x]]
set c1y [$c1 get y]
set c3y [$c3 get y]
set c1c3y [expr [$c3y - $c1y]]
set c1z [$c1 get z]
set c3z [$c3 get z]
set c1c3z [expr [$c3z - $c1z]]
set st [expr $frame]
puts $fil [list $st $c1c3x $c1c3y $c1c3z ]
$c3 delete
$c1 delete
}
close $fil
现在正在收到“无效的命令名称”“”错误。我哪里错了?
附加信息:我正在使用VMD运行此操作,以从加载的gromacs轨迹中提取坐标。
答案 0 :(得分:3)
在:
set c1c3z [expr [$c3z - $c1z]]
您尝试使用$c3z
和-
的内容作为参数运行$c1z
命令(并将其返回值作为参数传递给expr
)。
要等同于以前版本的代码,它将是:
set c1c3z [expr $c3z - $c1z]
但是,由于$c3z
似乎是空的(所以不是数字),您可能会遇到更多问题。
此处,$c3z
和$c1z
很可能为空,这意味着expr
会对" - "
表达式进行评估,您将会看到:
$ tclsh <<< 'expr " - "'
missing operand at _@_
in expression " - _@_"
如果正如Donal在评论中所建议的那样,你写的是:
set c1c3z [expr {$c3z - $c1z}]
相反,文字$c3z - $c1z
会传递给expr
而expr
会在尝试评估时提供更有用的错误消息:
$ tclsh <<< 'set a ""; expr {$a - $a}'
can't use empty string as operand of "-"
expr
TCL man page会为您提供更多信息,说明为什么通常会将{}
- 附带的表达式传递给它。