From: Henry Maddocks <hmaddocks@...>
Date: 2012-06-22T08:30:12+09:00
Subject: inject was Benchmark obsession?


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On 21/06/2012, at 9:50 AM, Ryan Davis wrote:

> Given #inject's other alias, #reduce, it is obvious that you don't use #inject for building up other objects. Even in a functional style of programming you'd _never_ see it building up anything. You'd see it REDUCING (folding) an object. If #inject is applied in a non-folding manner, it isn't functional, it is just dumb. Don't pretend otherwise (and if you do pretend otherwise, go read more books on lisp--start with SICP). The second I see a semicolon (or return) in an inject, I immediately suspect that someone is writing clevar/stupid code.
> 
> I don't have any recent examples from the list, but I'm on record in multiple mediums ranting against people who use #inject improperly. I'll make up one based on examples I've seen time and time again:

I come across this quite often, especially in Rails apps.

a = {:list => [1,2,3,4]}
b = {:list => [9,8,7,6,5]}

c = [a,b]

c.inject([]) {|memo, run| memo + run[:list] } 

I always cringe when I see it but I haven't found an alternative that is as clear and concise. 
collect and flatten looks ugly. I'd love to be able to do...

c.collect {|run| *run[:list]}


Henry


      

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<html><head></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; =
"><br><div><div>On 21/06/2012, at 9:50 AM, Ryan Davis =
wrote:</div><br><blockquote type=3D"cite"><div>Given #inject's other =
alias, #reduce, it is obvious that you don't use #inject for building up =
other objects. Even in a functional style of programming you'd _never_ =
see it building up anything. You'd see it REDUCING (folding) an object. =
If #inject is applied in a non-folding manner, it isn't functional, it =
is just dumb. Don't pretend otherwise (and if you do pretend otherwise, =
go read more books on lisp--start with SICP). The second I see a =
semicolon (or return) in an inject, I immediately suspect that someone =
is writing clevar/stupid code.<br><br>I don't have any recent examples =
from the list, but I'm on record in multiple mediums ranting against =
people who use #inject improperly. I'll make up one based on examples =
I've seen time and time again:<br></div></blockquote><br></div><div>I =
come across this quite often, especially in Rails =
apps.</div><div><br><font class=3D"Apple-style-span" face=3D"Courier">a =
=3D {:list =3D&gt; [1,2,3,4]}<br>b =3D {:list =3D&gt; =
[9,8,7,6,5]}<br><br>c =3D [a,b]<br><br>c.inject([]) {|memo, run| memo + =
run[:list] }&nbsp;<br></font><br></div><div>I always cringe when I see =
it but I haven't found an alternative that is as clear and =
concise.&nbsp;</div><div>collect and flatten looks ugly. I'd love to be =
able to do...</div><div><br></div><div><font class=3D"Apple-style-span" =
face=3D"Courier">c.collect {|run| =
*run[:list]}</font></div><div><br></div><div><br></div><div>Henry</div><di=
v><br></div><div><br></div>&nbsp; &nbsp; &nbsp;&nbsp;</body></html>=

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