英文:
Work arounds to printing negative zero in tcl
问题
我正在重新编写脚本的一部分，以在tcl中执行，因为有一个只能在tcl中使用的工具。在这段代码中，用户可以提供一个选项（-m用于镜像），以便将值沿y轴翻转。（基本上，所有x值都会乘以-1。）当打印出从这个翻转中得到的值时，我意识到我的输出中在原始脚本中有0.0000的地方有-0.0000。
我通过以下方式解决了这个问题：
if {$mirrored eq "t" && $text_x != 0} {
# 在tcl中，如果将0乘以-1，将得到-0，我们不希望出现这种情况
set text_x [expr {$text_x * -1.0}]
}
我对这个解决方案感到满意，但在我的if语句中包含这个特殊情况感觉有点奇怪。是否有更简洁、优雅或被接受的方法来做到这一点？或者其他任何方式吗？
英文:
I'm dealing with rewriting a portion of a script to execute in a tcl because of a tool that's only available in tcl. In this code, the user can provide an option (-m for mirrored) to flip values around the y axis. (Basically, all the x values get multiplied by -1.) When printing out the values that resulted from this flipping, I realized that my output had a -0.0000 wherever the original script had 0.0000.
I fixed this issue by not multiplying the x value by -1 if it's equal to zero as bellow:
if {$mirrored eq "t" && $text_x != 0} {
#in tcl if you multiply 0 by -1 you get -0 we don't want that
set text_x [expr {$text_x * -1.0}]
}
I am okay with this solution, but it feels a bit weird to include this one case in my if statement. Is there a more concise, elegant or accepted way of doing this? Or any other way at all?
答案1
得分: 3
Add zero:
复制您所述的行为：
% 设置 x 0
0
% 设置 y [expr {$x * -1.0}]
-0.0
以及解决方法：
% 设置 z [expr {$x * -1.0 + 0}]
0.0
英文:
Add zero:
Replicating your stated behaviour:
% set x 0
0
% set y [expr {$x * -1.0}]
-0.0
and the remedy
% set z [expr {$x * -1.0 + 0}]
0.0
答案2
得分: 0
是的，这个有点奇怪。我不知道Tcl为什么这样做。一个解决方法是简单地从零减去text_x
if {$mirrored eq "t"} {
set text_x [expr {0 - $text_x }]
}
一些例子：
% set text_x 0
0
% set text_x [expr {0 - $text_x }]
0
% set text_x 0.0
0.0
% set text_x [expr {0 - $text_x }]
0.0
% set text_x 1.2
1.2
% set text_x [expr {0 - $text_x }]
-1.2
% set text_x 15
15
% set text_x [expr {0 - $text_x }]
-15
英文:
Yeah, it's a funny one. I don't know the reasons why Tcl does this. One solution is to simply subtract text_x from zero
if {$mirrored eq "t"} {
set text_x [expr {0 - $text_x }]
}
Some examples:
% set text_x 0
0
% set text_x [expr {0 - $text_x }]
0
% set text_x 0.0
0.0
% set text_x [expr {0 - $text_x }]
0.0
% set text_x 1.2
1.2
% set text_x [expr {0 - $text_x }]
-1.2
% set text_x 15
15
% set text_x [expr {0 - $text_x }]
-15
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