int a = 0; (++a) = 10;// 为什么可以 (a++) = 10;//为什么不可以 前++为什么是一个左值,而后++为什么是一个右值, 前++是否即可以当作一个左值,又可以当作一个右值?? int x=y=z=1; x = y+++z; x? y? z? y+++z 是先(y++)+z 还是y+ (++z)??
本帖最后由 黑色阳光_cu 于 2010-12-17 13:36 编辑 [code]#!/bin/env perl use strict; use warnings; my $str = "abcdefg"; *front = \substr($str, 0, 1); *rear = \substr($str, -1, 1); our ($front, $rear); print "str: $str\n"; print "front: $front rear: $rear\n"; $front = 1; $rear = 2; print "str: $str\n"; print "front: $front rear: $rear\n"; $str = "new string"; print "str: $str\n"; print "...
大家帮我看看一条左连接语句,为什么会漏掉值呢? select a.uid,a.expiretime,a.servicetype,b.pcphonecity from T_W_ValueAddedService a left join DB.T_BasicInfo2 b on a.uid=b.uid and b.pccity in ('0755','0769','0750','0760','020') where a.expiretime>DATE_ADD(NOW(),INTERVAL 100 DAY) and servicetype='phone_paymonthly' and b.pccity is not null; 查询结果: +----------+---------------------+-----------------...
char * vtysh_prompt () { struct utsname names; static char buf[100]; const char*hostname; extern struct host host; hostname = host.name; &names= (struct utsname*)malloc(sizeof(struct utsname)); if (!hostname) { uname (&names); hostname = names.nodename; } snprintf (buf, sizeof buf, cmd_prompt (vty->node), hostname); return buf; } 为什么我这段代码会报错呢?...
这是个2.4下的驱动,现在要移到2.6下,我把寄存器的头拷到/asm/arch-s3c2410/下了,但是报出了以下的错误. 象这样的错误该如何改呢?请大侠给个示范 void spi_Init(eBandrate br) { S3C2410_GPECON &=~(0x3f<<22); S3C2410_GPECON |=(0x2a<<22); // init GPEIO is SPI Mode SPPRE0 &=0; //Cleae SPPRE0 ................(还有些enable/disable的函数) can.c:157: error: invalid lvalue in ...
这是个2.4下的驱动,现在要移到2.6下,我把寄存器的头拷到/asm/arch-s3c2410/下了,但是报出了以下的错误. 象这样的错误该如何改呢?请大侠给个示范 :-) void spi_Init(eBandrate br) { S3C2410_GPECON &=~(0x3f<<22); S3C2410_GPECON |=(0x2a<<22); // init GPEIO is SPI Mode SPPRE0 &=0; //Cleae SPPRE0 ................(还有些enable/disable的函数) can.c:157: error: invalid lvalue ...
[code]
#include