小编Dre*_*rew的帖子

执行与执行的命令后execSync，sh我注意到以下内容：

spawnSync /bin/sh ENOENT

bin 当前已添加到 PATH。

有什么想法吗？

• libcv-dev安装
• 10.04

关于可能定义以下内容的任何想法？

ahcarpenter@ahcarpenter-laptop:~$ g++ objectmarker.o -o objectmarker
objectmarker.o: In function `on_mouse(int, int, int, int, void*)':
objectmarker.cpp:(.text+0x12f): undefined reference to `cvCloneImage'
objectmarker.cpp:(.text+0x1d1): undefined reference to `cvRectangle'
objectmarker.cpp:(.text+0x1ea): undefined reference to `cvShowImage'
objectmarker.cpp:(.text+0x1f4): undefined reference to `cvReleaseImage'
objectmarker.o: In function `main':
objectmarker.cpp:(.text+0x391): undefined reference to `cvNamedWindow'
objectmarker.cpp:(.text+0x3aa): undefined reference to `cvSetMouseCallback'
objectmarker.cpp:(.text+0x4da): undefined reference to `cvLoadImage'
objectmarker.cpp:(.text+0x50f): undefined reference to `cvShowImage'
objectmarker.cpp:(.text+0x519): undefined reference to `cvWaitKey'
objectmarker.cpp:(.text+0x53f): undefined reference to `cvReleaseImage'
objectmarker.cpp:(.text+0x54e): undefined reference to `cvDestroyWindow'
objectmarker.cpp:(.text+0xd7f): undefined reference to `cvReleaseImage' …

所以我有三个文件:

jarvismarch.c
jarvismarchtools.c
jarvismarchtools.h

运行后make,我收到以下错误:

Andrew-Carpenters-Laptop:Independent Study ahcarpenter$ make
cc    -c -o jarvismarch.o jarvismarch.c
cc    -c -o jarvismarchtools.o jarvismarchtools.c
cc -o jarvismarch jarvismarch.o jarvismarchtools.o
ld: duplicate symbol _string1 in jarvismarchtools.o and jarvismarch.o for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [all] Error 1

string 1在...内宣布jarvismarchtools.c.jarvismarchtools.h包括在内jarvismarchtools.c以及jarvismarch.c.

关于如何解决此错误的任何想法？

内jarvismarchtools.h:

/*
    FILENAME: jarvismarchtools.h
    AUTHOR: Andrew H. Carpenter
    DATE: 2 …

每当返回NaN时,我希望返回的值为0.什么是实现此目的的最佳方法？

所以 (car '(2 3)) -> 2

(cdr '(2 3)) -> (3)

我应该使用哪种功能才能获得收益3？

(function-name '(2 3)) -> 3

有没有办法获取特定字段的每个不同值的计数？

for name in (SELECT DISTINCT name FROM table)
  SELECT COUNT name FROM table

不使用光标