Why don't Scala traits allow constructor parameters? -


i'm new scala, coming java, , reading traits. 1 thing gets mentioned traits don't (can't? won't?) have constructor parameters. curious know if there reason this.

coming long ago maths/computer-science background was wondering if inevitable consequence because of language design decision, or if conscious decision avoid inheritance/mix-in problem or another?

was hoping might know because feels there might interesting behind fact.

the other answers describe language; suspect question may "why designed in way".

i believe arises out of awkwardnesses , verboseness arise when extending multiple traits, overrides , types, , various mix-in strategies.

the cake pattern results in various traits providing missing bits each other in way totally invisible - design - in mixing class. , mixing can bi-directional, using self-types. construction of class traits can messy business compiler. scala trades simplicity of compiler design , implementation simplicity of language use , code reduction, , example.

so while there may simple, hierarchical cases having constructor might useful , sufficient, have redundant of other mechanisms more difficult, non-hierarchical scenarios.


Comments

Post a Comment

Popular posts from this blog

Payment information shows nothing in one page checkout page magento -

i using magento ver. 1.9.1.0 want remove shipping information , shipping method step 1 page checkout page. changed code in core file like in app\code\core\mage\checkout\block\onepage.php public function getsteps() { $steps = array(); $stepcodes = $this->_getstepcodes(); /* remove shipping address , shipping method */ $excludestep=array_diff($stepcodes,array('shipping','shipping_method')); //$excludestep=$stepcodes; if ($this->iscustomerloggedin()) { $stepcodes = array_diff($excludestep, array('login')); } foreach ($excludestep $step) { $steps[$step] = $this->getcheckout()->getstepdata($step); } return $steps; } and in app\code\core\mage\checkout\controllers\onepagecontroller.php public function savebillingaction() { if ($this->_expireajax()) { return; } if ($this->getrequest()-...
Read more

tcpdump - How to check if server received packet (acknowledged) -

Image
i running tcpdump on server capture traffic between server (servera) , remote server (serverb). not know how read output tcpdump. point out if serverb acknowledging packets being sent servera being received serverb? here tcpdump log: 2015-03-31 11:32:18.038284 ip (tos 0x0, ttl 64, id 30781, offset 0, flags [df], proto tcp (6), length 60) servera.14033 > serverb.8004: flags [s], cksum 0x02bd (correct), seq 337482636, win 14600, options [mss 1460,nop,nop,ts val 506588081 ecr 0,nop,wscale 7], length 0 0x0000: 4500 003c 783d 4000 4006 bae4 0a04 7a0e e.. servera.14033: flags [s.], cksum 0x3b2a (correct), seq 1742982091, ack 337482637, win 4140, options [mss 1380,nop,wscale 0], length 0 0x0000: 4500 0030 5ff2 0000 f606 5d3b cefd b48a e..0_.....];.... 0x0010: 0a04 7a0e 1f44 36d1 67e3 cbcb 141d 938d ..z..d6.g....... 0x0020: 7012 102c 3b2a 0000 0204 0564 0103 0300 p..,;*.....d.... 2015-03-31 11:32:18.078622 ip (tos 0x0, ttl 64, id 30782, offset 0, flags [...
Read more