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What is the difference between parent.frame() and parent.env() in R; how do they differ in call by reference?

由 元气小坏坏 提交于 2019-11-26 23:43:53
It would be helpful if someone can illustrate this with a simple example? Also, where would it be useful to use parent.frame() instead of parent.env() and vice versa. parent.env is the environment in which a closure (e.g., function) is defined. parent.frame is the environment from which the closure was invoked. f = function() c(f=environment(), defined_in=parent.env(environment()), called_from=parent.frame()) g = function() c(g=environment(), f()) and then > g() $g <environment: 0x14060e8> $f <environment: 0x1405f28> $defined_in <environment: R_GlobalEnv> $called_from <environment: 0x14060e8>

What's the return value from a function call if that function doesn't really provide one

由 怎甘沉沦 提交于 2019-11-26 18:33:48
问题 Let's say we have following code: int func(char str[], int len) { // Don't return anything here. } int main() { char str[] = "Hello"; int result = func(str, strlen(str)); printf("%d\n", result); } It will print some string value -1679929632 on my computer. And it changes from time to time when I execute. Can anyone explain why this happen? 回答1: If no return statement appears in a function definition, control automatically returns to the calling function after the last statement of the called

What is the difference between parent.frame() and parent.env() in R; how do they differ in call by reference?

由 微笑、不失礼 提交于 2019-11-26 12:20:33
问题 It would be helpful if someone can illustrate this with a simple example? Also, where would it be useful to use parent.frame() instead of parent.env() and vice versa. 回答1: parent.env is the environment in which a closure (e.g., function) is defined. parent.frame is the environment from which the closure was invoked. f = function() c(f=environment(), defined_in=parent.env(environment()), called_from=parent.frame()) g = function() c(g=environment(), f()) and then > g() $g <environment:

What is a stack map frame

由 我们两清 提交于 2019-11-26 10:09:16
问题 I\'ve recently been looking at The Java Virtual Machine Specifications (JVMS) to try to better understand the what makes my programs work, but I\'ve found a section that I\'m not quite getting... Section 4.7.4 describes the StackMapTable Attribute, and in that section the document goes into details about stack map frames. The issue is that it\'s a little wordy and I learn best by example; not by reading. I understand that the first stack map frame is derived from the method descriptor, but I

What is the direction of stack growth in most modern systems?

由 你离开我真会死。 提交于 2019-11-26 00:46:13
问题 I am preparing some training materials in C and I want my examples to fit the typical stack model. What direction does a C stack grow in Linux, Windows, Mac OSX (PPC and x86), Solaris, and most recent Unixes? 回答1: Stack growth doesn't usually depend on the operating system itself, but on the processor it's running on. Solaris, for example, runs on x86 and SPARC. Mac OSX (as you mentioned) runs on PPC and x86. Linux runs on everything from my big honkin' System z at work to a puny little
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