generator

问题 I have a construct of the form: pub enum Value { Nil, Str(String), Seq(Vec<Value>), } A Value is either null, a string, or a vector of other Value s, which can then in turn be any of the three options. I'd like to make a method that lazily iterates over each String in a Value , respecting nesting. My first attempt looks something like this: #![feature(generators)] #![feature(generator_trait)] use std::ops::{Generator, GeneratorState}; use std::pin::Pin; fn gen_to_iter<G>(g: G) -> impl

问题 I am looking for some free/oss to reverse engineer from DDL a data model diagram. My database is Oracle if that matters. Do any exist? 回答1: http://schemaspy.sourceforge.net/ 回答2: SQL Power architect has a GPL version (though it looks like they are releasing an 'Enterprise' edition soon) There is also FabForce's DBDesigner, though it is more geared to MySQL (but has some Oracle capability) 回答3: You could also look at sql-developer and data-modeler from Oracle. both are free http://www.oracle

问题 package com.sb.firstjpaexample.pojo; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.SequenceGenerator; import javax.persistence.Table; import javax.persistence.TableGenerator; @Entity @Table(name = "EMPLOYEE") public class Employee { @Id @TableGenerator(name = "TABLE_GEN", table = "SEQUENCE_TABLE", pkColumnName = "SEQ_NAME", valueColumnName

问题 I'm reading this question which asks if generators are thread-safe, and one answer said: It's not thread-safe; simultaneous calls may interleave, and mess with the local variables. Another answer shows that you can use a lock to ensure that only one thread uses the generator at a time. I'm new to multithreading. Can anyone devise an example to show what exactly happens when you use the generator without lock? For example, it doesn't seem to have any problems if I do this: import threading def

问题 It is very convenient to use Tasks to express a lazy collection / a generator. Eg: function fib() Task() do prev_prev = 0 prev = 1 produce(prev) while true cur = prev_prev + prev produce(cur) prev_prev = prev prev = cur end end end collect(take(fib(), 10)) Output: 10-element Array{Int64,1}: 1 1 2 3 5 8 13 21 34 However, they do not follow good iterator conventions at all. They are as badly behaved as they can be They do not use the returned state state start(fib()) == nothing #It has no state

问题 Is the following code for generating primes pythonic? def get_primes(n): primes=[False,False]+[True]*(n-1) next_p=(i for i,j in enumerate(primes) if j) while True: p=next(next_p) yield p primes[p*p::p]=[False]*((n-p*p)//p+1) Note that next(next_p) will eventually throw a StopIteration error which somehow ends the function get_primes. Is that bad? Also note that next_p is a generator which iterates over primes, however primes changes during iteration. Is that bad style? adding the following if

问题 Is the following code for generating primes pythonic? def get_primes(n): primes=[False,False]+[True]*(n-1) next_p=(i for i,j in enumerate(primes) if j) while True: p=next(next_p) yield p primes[p*p::p]=[False]*((n-p*p)//p+1) Note that next(next_p) will eventually throw a StopIteration error which somehow ends the function get_primes. Is that bad? Also note that next_p is a generator which iterates over primes, however primes changes during iteration. Is that bad style? adding the following if

问题 I have a generator function (Python) that works like this def Mygenerator(x, y, z, ...): while True: # code that makes two matrices based on sequences of input arrays yield (matrix1, matrix2) What I want to do is to add the output from this generator. This line does the job: M1, M2 = reduce(lambda x, y: x[0] + y[0], x[1] + y[1], Mygenerator(x, y, z, ...)) I would like to parallelize this to speed up the computations. It is important that the outputs from Mygenerator is reduced as it is

问题 I have some use cases in which I need to run generator functions without caring about the yielded items. I cannot make them non-generaor functions because in other use cases I certainly need the yielded values. I am currently using a trivial self-made function to exhaust the generators. def exhaust(generator): for _ in generator: pass I wondered, whether there is a simpler way to do that, which I'm missing? Edit Following a use case: def create_tables(fail_silently=True): """Create the

问题 Does ES6's support for tail call optimization cover tail calls in generators? Suppose I have this generator for integers >= 0: var nums = function* (n) { n = n || 0; yield n; yield* nums(n + 1); }; Currently, in Chrome and Firefox, it adds a stack level with each recursive call and eventually runs into a "maximum call stack size exceeded" error. Will this still occur once ES6 is fully implemented? (I know I can write the above generator iteratively and not run into the error. I'm just curious