Tcl之Math
expr is for Tcl to do math operations. It takes all of its arguments ("2 + 2" for example) and evaluates the result as a Tcl "expression". Many commands use expr
behind the scenes in order to evaluate test expressions, such as if
, while
and for
loops.
tip: enclosing the arguments to expr
in curly braces will result in faster code. So do expr {$i * 10}
instead of simply expr $i * 10
1) Operators
- + ~ !
Unary minus, unary plus, bit-wise NOT, logical NOT. None of these operators may be applied to string operands, and bit-wise NOT may be applied only to integers.
** Exponentiation (works on both floating-point numbers and integers)
- * / %
- Multiply, divide, remainder. None of these operators may be applied to string operands, and remainder may be applied only to integers. The remainder will always have the same sign as the divisor and an absolute value smaller than the divisor.
+ - Add and subtract. Valid for any numeric operands.
- << >> Left and right (bit) shift. Valid for integer operands only.
- < > <= >=
- Relational operators: less, greater, less than or equal, and greater than or equal. Each operator produces 1 if the condition is true, 0 otherwise. These operators may be applied to numeric operands as well as strings, in which case string comparison is used.
- eq ne in ni
- compare two strings for equality (
eq
) or inequality (ne
). and two operators for checking if a string is contained in a list (in
) or not (ni
). These operators all return 1 (true) or 0 (false). Using these operators ensures that the operands are regarded exclusively as strings (and lists), not as possible numbers.
- & Bit-wise AND. Valid for integer operands only.
^ Bit-wise exclusive OR. Valid for integer operands only.
| Bit-wise OR. Valid for integer operands only.
&& Logical AND. Produces a 1 result if both operands are non-zero, 0 otherwise. Valid for numeric operands only (integers or floating-point).
|| Logical OR. Produces a 0 result if both operands are zero, 1 otherwise. Valid for numeric operands only (integers or floating-point).
x?y:z
If-then-else. If x evaluates to non-zero, then the result is the value of y. Otherwise the result is the value of z. The x operand must have a numeric value.
2) Example
set X 100 ; # 100
set Y 256 ; # 256
set Z [expr {$Y + $X}] ; # 356
set Z_LABEL "$Y plus $X is " ; # 256 plus 100 is 356 puts "$Z_LABEL $Z"
puts "The square root of $Y is [expr { sqrt($Y) }]\n" ; # The square root of 256 is 16.0
# Because of the precedence rules "5 + -3 * 4" is: -7
puts "Because of the precedence rules \"5 + -3 * 4\" is: [expr {-3 * 4 + 5}]"
# Because of the parentheses "(5 + -3) * 4" is: 8
puts "Because of the parentheses \"(5 + -3) * 4\" is: [expr {(5 + -3) * 4}]" set A 3
set B 4
14 # The hypotenuse of a triangle: 5.0
puts "The hypotenuse of a triangle: [expr {hypot($A,$B)}]"
# The trigonometric functions work with radians ...
#
set pi6 [expr {3.1415926/6.0}]
puts "The sine and cosine of pi/6: [expr {sin($pi6)}] [expr {cos($pi6)}]" #
# Working with arrays
#
set a(1) 10
set a(2) 7
set a(3) 17
set b 2
puts "Sum: [expr {$a(1)+$a($b)}]"
Tcl之Math的更多相关文章
- 用Tcl/Tk脚本计算圆周率
读了阮一峰的蒙特卡罗方法入门,用概率统计的方式求解棘手的数学问题还挺有意思的,尤其是利用正方形和它的内切圆之间的面积关系来建模求解圆周率的方法精巧又简单,比投针实验好理解也好实现多了.建模可不是M ...
- Floating Point Math
Floating Point Math Your language isn't broken, it's doing floating point math. Computers can only n ...
- JavaScript中Math对象的方法介绍
1.比较最值方法 比较最值有两种方法,max() 和 min() 方法. 1.1 max() 方法,比较一组数值中的最大值,返回最大值. var maxnum = Math.max(12,6,43,5 ...
- JavaScript Math和Number对象
目录 1. Math 对象:数学对象,提供对数据的数学计算.如:获取绝对值.向上取整等.无构造函数,无法被初始化,只提供静态属性和方法. 2. Number 对象 :Js中提供数字的对象.包含整数.浮 ...
- Chrome V8引擎系列随笔 (1):Math.Random()函数概览
先让大家来看一幅图,这幅图是V8引擎4.7版本和4.9版本Math.Random()函数的值的分布图,我可以这么理解 .从下图中,也许你会认为这是个二维码?其实这幅图告诉我们一个道理,第二张图的点的分 ...
- Math.random()
Math.random() 日期时间函数(需要用变量调用):var b = new Date(); //获取当前时间b.getTime() //获取时间戳b.getFullYear() //获取年份b ...
- Math.abs()方法 取绝对值
定义和用法 abs() 方法可返回数的绝对值. 语法 Math.abs(x) 参数 描述 x 必需.必须是一个数值. 返回值 x 的绝对值. 实例 在本例中,我将取得正数和负数的绝对值: <sc ...
- Tcl internal variables
Tcl internal variables eryar@163.com 在Tcl中内置了一些变量,并赋予了一定的功能.内置变量列表如下: 变量名称 功能描述 argc 指命令行参数的个数. argv ...
- C标准头文件<math.h>
定义域错误可以理解为超出了函数的适用范围,如果发生了定义域错误,设errno为EDOM 如果结果不能表示为double值,则发生值域错误,如果结果上溢,则函数返回HUGE_VAL的值,设errno为E ...
随机推荐
- js中的封装、继承、多态
Javascript是一门解释型的语言,是基于对象的,并不是真正的面向对象的语言,对变量类型的应用也是宽松的,其实它同样可以模拟面向对象的功能: 1 function myfun1(){ 2 ...
- SQLite数据库基本操作
SQLite 是一个开源的嵌入式关系数据库,实现自包容.零配置.支持事务的SQL数据库引擎. 其特点是高度便携.使用方便.结构紧凑.高效.可靠. 与其他数据库管理系统不同,SQLite 的安装和运行非 ...
- mysql复制延迟监控脚本
#!/bin/sh #ocpyang@126.com #repdelay.sh #查看复制延迟详细多少event #####1.juede the rep slave status export bl ...
- Java内存问题的一些见解
在Java中,内存泄露和其它内存相关问题在性能和可扩展性方面表现的最为突出.我们有充分的理由去具体地讨论他们. Java内存模型--或者更确切的说垃圾回收器--已经攻克了很多内存问题. 然而同一时候, ...
- javascript的Date时差
当有日期字符串形如: var dt = "2015-03-16T23:59:59";//注意其中有个T,这是什么表示法?不清楚,可能是GMT标准时 然后转换成日期对象,系统会自动加 ...
- 关于The hierarchy of the type TestBeforeAdvice is inconsistent的问题
今天准备写一个spring aop的demo,创建了TestBeforeAdvice类,该类实现了MethodBeforeAdvice接口,eclipse报了"The hierarchy o ...
- 关于Domain Sepcific Lang
今天在看一些关于CO的东东 里面提到,用从语言派生出来的领域语言再去编写代码会大大加速开发进程 PHP应该是个典型的领域语言(Perl之于文本处理也是这样),虽然不是从什么其他领域派生出来的,但是使用 ...
- JLabel作为展现元素时需要注意的事项
如果没有内容,JLabel默认透明就无法作为点击区域了,所以为了让其可以响应鼠标事件需要设置 setOpaque(true) 这样就可以响应鼠标事件了 (吐槽一下,多年以前在大学做个web地图导航的网 ...
- IDEA 单元测试
下载所需的两个 jar 包,下载地址:Download and Install · junit-team/junit4 Wiki · GitHub junit-4.12.jar hamcrest-co ...
- CodeFirst建模:DataAnotation
示例一 新建一个控制台应用程序,并安装entityframework 新建一个文件Blog.cs类,输入以下代码: using System.ComponentModel.DataAnnotation ...