Consider a tail recursive factorial implementation in C: #include <stdio.h> unsigned long long factorial(unsigned long long fact_so_far, unsigned long long count, unsigned long long max_count){ if (max_count==0 || max_count==1 || count >= max_count) return fact_so_far; else { printf("%llu %p n", count, &factorial); return factorial(fact_so_far * count, ++c
考虑一下C中的尾递归阶乘实现: #include <stdio.h> unsigned long long factorial(unsigned long long fact_so_far, unsigned long long count, unsigned long long max_count){ if (max_count==0 || max_count==1 || count >= max_count) return fact_so_far; else { printf("%llu %p n", count, &factorial); return factorial(fact_so_far * count, ++count, max_count); } } in
From Optimization Compiler on Wikipedia, Compiler optimization is generally implemented using a sequence of optimizing transformations , algorithms which take a program and transform it to produce a semantically equivalent output program that uses fewer resources. and GCC has a lot of optimization options. I'd like to study the generated assembly (the one -S gives) after each optimizati
从维基百科上的优化编译器, 编译器优化通常是使用一系列优化转换来实现的,这些转换算法采用一个程序并将其转换为产生语义等价的输出程序,从而使用较少的资源。 而GCC有很多优化选项。 我想在使用不同的标志(例如-O1 , -O2 , -O3等)进行编译时,在GCC执行每次优化之后研究生成的程序集(一个-S给出)。 我怎样才能做到这一点? 编辑:我的输入将是C代码。 中间表示可以使用-fdump-tree-all开关保存到文件中。
I almost understand how tail recursion works and the difference between it and a normal recursion. I only don't understand why it doesn't require stack to remember its return address. // tail recursion int fac_times (int n, int acc) { if (n == 0) return acc; else return fac_times(n - 1, acc * n); } int factorial (int n) { return fac_times (n, 1); } // normal recursion int
我几乎了解尾递归如何工作,以及它和正常递归之间的区别。 我只是不明白为什么它不需要堆栈来记住它的返回地址。 // tail recursion int fac_times (int n, int acc) { if (n == 0) return acc; else return fac_times(n - 1, acc * n); } int factorial (int n) { return fac_times (n, 1); } // normal recursion int factorial (int n) { if (n == 0) return 1; else return n * factorial(n - 1); }
F# supports a type constraint for "unmanaged". This is not the same as a value type constraint like "struct" constraints. MSDN notes that the behavior of the unmanaged constraint is: The provided type must be an unmanaged type. Unmanaged types are either certain primitive types (sbyte, byte, char, nativeint, unativeint, float32, float, int16, uint16, int32, uint32, int64,
F#支持“非托管”的类型约束。 这与“结构”约束等值类型约束不同。 MSDN注意到非托管约束的行为是: 提供的类型必须是非托管类型。 非托管类型可以是某些基本类型(sbyte,byte,char,nativeint,unativeint,float32,float,int16,uint16,int32,uint32,int64,uint64或decimal),枚举类型,nativeptr <_>泛型结构的字段都是非托管类型。 在进行平台调用时,这是一个非常方便的约束类型,并且我希望C#有一种
In the past years I've occasionally been wondering what equivalent of the (in)famous DLL_PROCESS_ATTACH was available in the .NET world. Any documentation I have says, slightly simplified, that the earliest entry point to a class is the static constructor (cctor), but you cannot influence when it is called, nor can you define one cctor that's guaranteed to be called prior to any other cc
在过去的几年中,我偶尔会想知道在.NET世界中什么样的(着名的) DLL_PROCESS_ATTACH可用。 我所说的任何文档都略有简化,最早的类入口点是静态构造函数(cctor),但不能影响何时调用它,也不能定义一个保证在任何其他cctor之前被调用的cctor或者字段初始值设定项hack,如果从未使用该类,甚至可能根本不会调用它。 所以,如果你想在你的程序集的任何方法被调用之前保证某些东西已经被初始化了,并且你不想为你的程序集中的
Can somebody clarify the C# is keyword please. In particular these 2 questions: Q1) line 5; Why does this return true? Q2) line 7; Why no cast exception? public void Test() { object intArray = new int[] { -100, -200 }; if (intArray is uint[]) //why does this return true? { uint[] uintArray = (uint[])intArray; //why no class cast exception? for (in
有人可以澄清C# is关键字请。 特别是这2个问题: Q1)第5行; 为什么这返回真实? Q2)第7行; 为什么没有演员异常? public void Test() { object intArray = new int[] { -100, -200 }; if (intArray is uint[]) //why does this return true? { uint[] uintArray = (uint[])intArray; //why no class cast exception? for (int x = 0; x < uintArray.Length; x++)
I was practicing my coding chops today and solving the "remove all elements of a certain value from a linked list" problem today. The solution I came up with was public void RemoveAll ( T val ) { if(_root == null) return; if(_root.Value == val) { _root = _root.Next; RemoveAll(val); } Node last = _root, cur = _root.Next;
我今天正在练习编码,并且今天解决了“从链表中删除某个值的所有元素”的问题。 我提出的解决方案是 public void RemoveAll ( T val ) { if(_root == null) return; if(_root.Value == val) { _root = _root.Next; RemoveAll(val); } Node last = _root, cur = _root.Next; while(cur != null) { if(cur.Value == val) last.Next = cur.
I am working on project where we have to work out delivery times based on rules in the database. The same day can have a few possibilities (same day deliveries) but also Fridays, Saturdays don't have rules so we have to look ahead and find the Monday rule. Sorry for long winded explanation ... To add to complexity we also calculate when the item can be collected at the delivery point so
我正在开发项目,根据数据库中的规则来制定交付时间。 同一天可能有一些可能(当天交付),但星期五,星期六也没有规则,所以我们必须向前看并找到星期一规则。 对不起长时间的解释... 为了增加复杂性,我们还计算何时可以在交货点收集物品,以便根据上午/下午的担保计算接货时间,并确保该地点是开放的,而不是假期...... 当我最初编写逻辑时,我创建了一个采用日期并计算所有这些值并返回我们的计算模型的方法。 就在
ECMA-335, III.2.4 specifies tail. prefix that can be used in recursive functions. However, I could not find its usage neither in C# nor in F# code. Are there any example of using in? You are not going to find it in any code produced by the current MS C# compiler. You will find it in code produced from the F# compiler, but not as much as you might expect, for almost opposite reasons. Now,
ECMA-335,III.2.4规定了tail. 可以在递归函数中使用的前缀。 但是,我无法在C#和F#代码中找到它的用法。 有没有使用的例子? 您不会在当前MS C#编译器生成的任何代码中找到它。 您可以从F#编译器生成的代码中找到它,但由于几乎相反的原因,没有您期望的那么多。 现在,首先要纠正你的陈述中的一个错误: ECMA-335,III.2.4规定了尾巴。 可以在递归函数中使用的前缀。 这不完全正确。 tail. 前缀可用于被叫
The following function I wrote causing the program to crash due to the stack overflow, although the recursion is finite. public static void Key(char[] chars, int i, int l, string str) { string newStr=null; for(int j=0; j<l; j++) newStr+=chars[i/(int)Math.Pow(68, j)%68]; if(newStr==str) return; Key(chars, ++i, l, newStr); } When I call the method with these
我写的以下函数导致程序因堆栈溢出而崩溃,尽管递归是有限的。 public static void Key(char[] chars, int i, int l, string str) { string newStr=null; for(int j=0; j<l; j++) newStr+=chars[i/(int)Math.Pow(68, j)%68]; if(newStr==str) return; Key(chars, ++i, l, newStr); } 当我用这些参数调用方法时,一切正常: Key(chars, 0, 4, "aaaa"); 但是当涉及更多的调用时,它会抛