I'm trying to get my if statement to catch when a person enters an input that says quit or exit but it isn't. Here is my code
use strict;
use warnings;
my $g=0;
my $rn = int(rand(25));
until ($g == $rn) {
$g = <STDIN>;
if ($g == $rn) {
print "You got it";
} elsif (chomp($g) eq "quit" || chomp($g) eq "exit") {
print "it triggered";
} elsif ($g > $rn) {
print "incorrect its lower";
} elsif ($g <$rn) {
print "incorrect its higher";
} else {
print "end";
}
}
}
The
elsif (chomp($g) eq "quit" || chomp($g) eq "exit) {
line is not catching despite numerous attempts to catch the error. I've tried printing off what the program is seeing to no avail. What I get in response when I type in quit from the strict/warnings is that
argument "quit\n" isn't numeric in numeric eq (==) at ./program24.pl line 30, <STDIN> line 1.
argument "quit" isn't numeric in numeric gt (>) at ./program24.pl line 36, line 1.
I've looked at several of the other posts on this but nothing from them seems to be whats causing this. What am I doing wrong?
答案 0 :(得分:5)
chomp
命令删除尾随换行符,但作用于变量本身,其返回值是删除的字符数。通常,只需要chomp
变量或表达式一次。由于perl中有两种类型的比较运算符,数字< <= == != >= >
,字符串lt le eq ne ge gt
,我们应该在执行比较之前确定我们具有哪种值以避免触发警告。
如果$guess =~ m|^\d+$|
是正整数或0,$guess
语句返回true,方法是检查$guess
的字符串化版本是否仅由数字组成。
由于rand
返回小数0 <= x < 1
,因此rand 25
将返回一个数字
0 <= x < 25
因此永远无法联系到25
。 int
会将数字向下舍入为零,因此int rand 25
将返回(0,1,2,...,22,23,24)
之一。要获得(1,2,...,25)
,我们需要添加1
。
像$g
这样的单字母变量通常是一个坏主意,因为它们没有传达变量的含义,如果它在代码中变得普遍,则稍后重命名会更加困难。我用$guess
替换了它。在perl中,唯一普遍接受的单字母变量是$a
和$b
,它们是全局的并用于比较函数,以及perl预定义变量,如$_
,$@
等。perldoc perlvar
#!/usr/bin/perl
use strict;
use warnings;
my $guess = 0;
my $int_max = 25;
my $rn = int(rand($int_max)) + 1;
print "I have picked a number between 1 and $int_max, can you guess it?\n";
until ($guess == $rn) {
chomp ($guess = <STDIN>);
if ( $guess =~ m|^\d+$| ) {
# Answer is an integer
if ( $guess == $rn ) {
print "You got it!\n";
} elsif ( $guess > $rn ) {
print "Too high, try again.\n";
} elsif ( $guess < $rn ) {
print "Too low, try again.\n";
}
} else {
# Anything else
if ('quit' eq $guess or 'exit' eq $guess) {
print "Exiting...\n";
exit 0;
} else {
print "Unclear answer : '$guess' : try again!\n";
$guess = 0; # So the equality test does not warn
}
}
}