关于eq与==的疑问

netrookie

想知道它们之间的区别？
>,>=,<,<=分别对应的是什么？
新手，刚看书， 碰到疑问， 请教……

[ 本帖最后由 netrookie 于 2009-11-24 21:27 编辑 ]

ttcn_cu

数字用等等，字符串用eq

netrookie

第二个问题？
>:gt?
>=:ge?
<:lt?
<=:le?
还有不等于!=:ne?
是吗？

ttcn_cu

http://perldoc.perl.org/perlop.html

兰花仙子

原帖由 netrookie 于 2009-11-24 21:34 发表
第二个问题？
>:gt?
>=:ge?

是的。
shell里数字比对用eq，字符比对用==（我记得是）。
但perl是反过来的。

netrookie

well, cool……
谢谢，原来还有这么个好地方。

Binary "<" returns true if the left argument is numerically less than the right argument. Binary ">" returns true if the left argument is numerically greater than the right argument. Binary "<=" returns true if the left argument is numerically less than or equal to the right argument. Binary ">=" returns true if the left argument is numerically greater than or equal to the right argument. Binary "lt" returns true if the left argument is stringwise less than the right argument. Binary "gt" returns true if the left argument is stringwise greater than the right argument. Binary "le" returns true if the left argument is stringwise less than or equal to the right argument. Binary "ge" returns true if the left argument is stringwise greater than or equal to the right argument.

netrookie

不对……

Equality Operators Binary "==" returns true if the left argument is numerically equal to the right argument. Binary "!=" returns true if the left argument is numerically not equal to the right argument. Binary "<=>" returns -1, 0, or 1 depending on whether the left argument is numerically less than, equal to, or greater than the right argument. If your platform supports NaNs (not-a-numbers) as numeric values, using them with "<=>" returns undef. NaN is not "<", "==", ">", "<=" or ">=" anything (even NaN), so those 5 return false. NaN != NaN returns true, as does NaN != anything else. If your platform doesn't support NaNs then NaN is just a string with numeric value 0.    1. perl -le '$a = "NaN"; print "No NaN support here" if $a == $a'    2. perl -le '$a = "NaN"; print "NaN support here" if $a != $a' Binary "eq" returns true if the left argument is stringwise equal to the right argument. Binary "ne" returns true if the left argument is stringwise not equal to the right argument.

[ 本帖最后由 netrookie 于 2009-11-24 21:47 编辑 ]

jiang_ocean

和shell相反。

DQP

都是perl的类型系统惹的祸  

szedwin

原帖由 netrookie 于 2009-11-24 21:22 发表
想知道它们之间的区别？
>,>=,

> gt  greater than
< lt   less than
>= ge  greater equal
<= le    less equal

英文不知道对不对...