小编Gab*_*iel的帖子

通常,我们A[i], A[j] = A[j], A[i]用来交换.

这有时可能无效.例如,

A=[1, 2]
A[0], A[A[0]] = A[A[0]], A[0]

将失败.为什么会失败以及如何解释赋值？

升级到OS X Mavericks后,所有已安装的端口都已过时.我不能再使用我的gcc,请帮忙.

The following installed ports are outdated:
bzip2                          1.0.6_0 < 1.0.6_0  (platform darwin 12 != darwin 13)  
cctools                        839_2 < 839_2  (platform darwin 12 != darwin 13)  
cctools-headers                839_0 < 839_0  (platform darwin 12 != darwin 13)  
cloog                          0.18.0_0 < 0.18.0_0  (platform darwin 12 != darwin 13)  
curl                           7.33.0_0 < 7.33.0_0  (platform darwin 12 != darwin 13)  
curl-ca-bundle                 7.33.0_0 < 7.33.0_0  (platform darwin 12 != darwin 13)  
cyrus-sasl2                    2.1.25_4 < 2.1.25_4  (platform darwin 12 != darwin 13)  
db46 …