overflow | 易学教程

Create method which checks if x + y will overflow using bitwise operations

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问题 I need to create a method in C using bitwise operations which checks if x + y will overflow or not. I can only use a maximum of 20 of the following operations; ! ~ & ^ | + << >> Keep in mind I have to test for both negative and positive numbers. I've tried several times to make it work. Is my logic sound? I'm going by: if (x + y) is less than x, then it has overflowed. Based on that logic, I wrote this; int addOK(int x, int y) { int sum = x + y; int nx = ((~x) + 1); int check = (sum + nx)>>31

How to detect an overflow in C++?

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问题 I just wonder if there is some convenient way to detect if overflow happens to any variable of any default data type used in a C++ program during runtime? By convenient, I mean no need to write code to follow each variable if it is in the range of its data type every time its value changes. Or if it is impossible to achieve this, how would you do? For example, float f1=FLT_MAX+1; cout << f1 << endl; doesn't give any error or warning in either compilation with "gcc -W -Wall" or running. Thanks

常规流之块级格式化上下文（Block Formatting Contexts）

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　　在css2.1中，常规流包括块框（block boxes）的块格式化（block formatting）,行内框（inline boxes）的行内格式化（inline formatting），块级框（block-level-boxes）或行内级框（inline-level-boxes）的相对定位。常规流中的框属于一个格式化上下文，可能是块或者是行内，但不能同时都是。块级框参与块级格式化上下文，行内级框参与行内级格式化上下文。今天我们先来说说块级格式化上下文，也就是我们常说的BFC。一.形成块级格式化上下文绝对定位元素（fixed其实是absolute的一个子集） display为inline-block，table-cell，table-caption，flex，inline-flex（这里有一点要注意的，display-table本身不会形成BFC，但是它会产生匿名框，其中包含的dispaly：table-cell元素会形成BFC） overflow不为visible 根元素 float属性不为none 　这里要说明的是这些是形成块格式化上下文，而不是说是参与块级格式化上下文，这两个概念很容易弄混，大家可以仔细体会下。块格式化上下文是一个独立的渲染区域，而且只会有块级框（block-level box）来参与，它规定内部的块级框如何布局

Is arithmetic overflow equivalent to modulo operation?

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问题 I need to do modulo 256 arithmetic in C. So can I simply do unsigned char i; i++; instead of int i; i=(i+1)%256; 回答1: No. There is nothing that guarantees that unsigned char has eight bits. Use uint8_t from <stdint.h> , and you'll be perfectly fine. This requires an implementation which supports stdint.h : any C99 compliant compiler does, but older compilers may not provide it. Note: unsigned arithmetic never overflows, and behaves as "modulo 2^n". Signed arithmetic overflows with undefined

css overflow - only 1 line of text

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问题 I have div with the following css style: width:335px; float:left; overflow:hidden; padding-left:5px; When I insert, into that div , a long line of text, it's breaking to a new line and displays all the text. What I want is to have only one line of text that will not line-break. When the text is long, I want this overflowing text to disappear. I was thinking about setting the height but it seems to be wrong. Maybe if I add height that is the same as the font, it should work and not cause any

css overflow - only 1 line of text

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Multilevel Nav Menu not showing 3rd level

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问题 the third level of my menu doesn't show up when hovering the 2nd level. I know that this is because overflow:hidden is styled on the 2nd level ul , however, if I make overflow:visible then the transition effect with max-height doesn't work properly. I have tried making overflow-y:hidden with overflow-x:visible and that does allow the transition to still work but adds a horizontal scroll bar that you need to scroll to the right to see the 3rd level menu. If you can solve this, i have another

Overflow: auto does not work in Firefox

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问题 I have a table. Its <td> have overflow: auto . The width is set to be 100px. In Firefox only , text that exceeds 100px is not hidden and replaced with a scrollbar. How can I hide content and have a scrollbar when it exceeds the width of its container? http://jsfiddle.net/be6tM/10/ 回答1: this question from here maybe solve your problem nickb answer: "Try wrapping it in a <div> . I'm pretty sure the overflow attribute is not defined for a <td> element, at least in HTML4 it's not." try to put

HTML fieldset allows children to expand indefinitely

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问题 I want to put a scrollable box inside of a fieldset , but I’ve run into a quirk and I can’t figure out my way around it. When you put your scrollable div inside of a fieldset , the fieldset expands instead of making the scrollable element scroll. Here’s a test case. The following expands indefinitely (boo): <div style="width: 300px; overflow: hidden;"> <fieldset> <div style="overflow: scroll; white-space: nowrap;"> Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed lorem arcu,

浮层滚动问题

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引子使用 position transform 实现从右边滑出的 h5 浮层效果，但在手机浏览器上左右滑动时，页面产生了左右滚动条，浮层也出来了。这是问题页面，移动端访问如下：这个现象不应该出现，问题好解决，但为什么会这样？想了一下，好像知道相关点，但又讲不清，所以在此梳理一下。 Origin My GitHub 原因产生了滚动，很自然的就会想到 overflow 属性，那么就先来了解一下。 overflow 属性指定了块容器元素的内容溢出时是否被剪裁，是 overflow-x 和 overflow-y 的简写。 Name overflow 可取值 visible 默认值 visible 适用于块级容器和建立了格式化上下文的盒子继承性无 visible ：这个值表示内容不会被剪切，可能会在盒子之外渲染。 hidden ：这个值表示内容被剪切，并且不应提供滚动用户界面来查看剪裁区域之外的内容。 scroll ：这个值表示内容被剪切，并且如果用户代理使用在屏幕上可见的滚动机制（例如滚动条或窗格），则无论盒子中的任何内容是否被剪裁，都应为盒子显示该机制。这是为了避免滚动条在一个动态环境中，出现和消失造成的任何问题。当指定这个值且目标媒介是打印时，溢出的内容可能会被打印，也可能不会打印。当用在 table boxes 时，这个值跟 visible 作用一致。 auto