请教浮点数变量内插问题

hailongchang

假如有类似于1.0000这样的浮点数，当作为变量内插后，可能会被显示为整数1，例如下面的代码：

1. 
   
2. use 5.010;
   
3. use strict;
   
4. use warnings;
   
5. 
   
6. my $ft = 1.0000;
   
7. 
   
8. my $str = "this is a float: " . $ft;
   
9. 
   
10. say $str;
    

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这会在终端显示为this is a float: 1,我需要让浮点数原样显示出来，this is a float: 1.0000，有没有快捷办法？在这个例子中printf就可以满足需求，可我需要在更复杂的情况下内插变量，比如在正则表达式的替换操作中内插一个这样的浮点数变量，改如何做，请教大家！

我的环境是Strawberry Perl 5.16.1

wsxedcer

回复 1# hailongchang


    将数字当成字符串使用

hailongchang

能说的详细点吗，就比如我的这个例子，不用printf，该如何做呢？回复 2# wsxedcer


   

tkgp

回复 1# hailongchang

1. #!/usr/bin/env perl
   
2. use Math::FixedPrecision;
   
3. my $a=new Math::FixedPrecision("1.000");
   
4. print "this is float: $a\n";
   
5. 
   
6. this is float: 1.000

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kiwivip

‘1.0000’ ？

tkgp

回复 4# tkgp
这个好没说服力，重写个

1. #!/usr/bin/env perl
   
2. use Math::FixedPrecision;
   
3. my $a=new Math::FixedPrecision("1.000");
   
4. my $b=$a*3;
   
5. print "this is float: ".$b."\n";
   
6. 
   
7. this is float: 3.000

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jason680

回复 1# hailongchang

How about sprintf

$ perl -e 'use v5.10;$ft = 1.0000;my $str = sprintf("this is a float: %.4f", $ft);say $str'
this is a float: 1.0000

hailongchang

回复 7# jason680

这样也可以，就是要引入一个新的变量，稍显麻烦


   

hailongchang

回复 6# tkgp

这个方法不错，受教了，多谢！

   

jason680

回复 8# hailongchang

sometime it also be changed ...

$ cat fixedPrecision.pl
#!/usr/bin/env perl
use strict;
use warnings;

use Math::FixedPrecision;

my $na=new Math::FixedPrecision("1.000");
my $nb=$na*3.3/7;
print "this is float: ". $na . "\n";
print "this is float: ". ($na *3.3) . "\n";
print "this is float: ". (3.3 * $na) . "\n";
print "this is float: ". ($nb) . "\n";
print "this is float: ". ($na*3.3/7) . "\n";

$ perl fixedPrecision.pl
this is float: 1.000
this is float: 3.3
this is float: 3.3
this is float: 0.5
this is float: 0.5