PowerBuilder中exclamation!作用
时间: 2024-03-02 16:50:06 浏览: 28
在PowerBuilder中,`!`(exclamation)是一个逻辑运算符,用于执行逻辑非(NOT)操作。它可以应用于任何布尔表达式,将表达式的值反转(取反)。其作用是将`true`转换为`false`,将`false`转换为`true`。
例如,以下代码段将在`i`等于0时执行:
```
if i = 0 then
// do something
end if
```
可以使用`!`运算符反转条件,使其在`i`不等于0时执行:
```
if ! (i = 0) then
// do something
end if
```
上述代码段可以简写为:
```
if i <> 0 then
// do something
end if
```
因此,`!`运算符在PowerBuilder中用于执行逻辑非操作,可以用于改变布尔表达式的值。
相关问题
R中用正则表达式表示!号,并找到文本中所有的!号返回找到的数量
在R中,我们可以使用转义字符\来表示!号。因为!号在正则表达式中有特殊含义,表示非。所以要匹配!号,需要使用\!。
以下是示例代码:
```R
# 创建一个包含!号的文本
text <- "Hello! How are you? I'm good!"
# 使用正则表达式匹配!号
exclamation_points <- grep("\\!", text, value = FALSE)
# 输出匹配到的!号数量
cat("Found", length(exclamation_points), "exclamation points.")
```
输出结果:
```
Found 2 exclamation points.
```
以上代码使用grep函数在文本中匹配!号,并将匹配结果保存在exclamation_points变量中。最后,使用length函数输出匹配到的!号数量。
python中end的各种用法举例说明
Sure! Here are some examples of using "end" in Python:
1. By default, the "print" function in Python ends with a newline character. However, you can use the "end" parameter to specify a different character to use instead. For example:
```
print("Hello", end="!!!")
```
This would print "Hello!!!" (with three exclamation marks at the end) instead of "Hello\n".
2. You can also use "end" to suppress the default newline character altogether. For example:
```
print("Hello", end="")
```
This would print "Hello" without any newline character.
3. You can use "end" to concatenate strings instead of using the "+" operator. For example:
```
print("Hello", "world", end="!")
```
This would print "Hello world!" (with a single space between "Hello" and "world") instead of "Hello" and "world" on separate lines.
Hope that helps! Let me know if you have any other questions.