# "&prock", not "&block" **URL:** \ **Category:** Ruby\ **Created:** [November 15, 2007, 2:28am UTC](https://www.ruby-forum.com/t/prock-not-block/120237 "2007-11-15T02:28:18Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![S-gw](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/ed655f/32.png) [@S-gw](https://www.ruby-forum.com/u/S-gw)\ **Post date:** [November 15, 2007, 2:28am UTC](https://www.ruby-forum.com/t/prock-not-block/120237/1 "2007-11-15T02:28:18Z")
In all of the code below, “prock” by itself is always a proc, while the combination “&prock” is always a block: ``` def my_proc &prock # accepts a block prock # returns a proc end prock = my_proc { p "Hello, world" } prock.call def doit &prock # param is redundant, but illustrative yield # yields to &prock, a block end doit &prock # same as 'doit { p "Hello, world" }' ``` So, it seems to me that “prock” above is distinctly clearer than “block”. (“proc” would be better still, but it’s taken.) My only problem with “prock” is that my eye tends to scan it as p-rock instead of the desired proc-k. But it still seems better than “block”. Any other ideas? “proce” perhaps? “procc”? ---
**Author:** ![S-gw](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/ed655f/32.png) [@S-gw](https://www.ruby-forum.com/u/S-gw)\ **Post date:** [November 15, 2007, 3:48am UTC](https://www.ruby-forum.com/t/prock-not-block/120237/2 "2007-11-15T03:48:56Z")
On Nov 14, 8:28 pm, Greg W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > instead of the desired proc-k. But it still seems better than “block”. > Any other ideas? “proce” perhaps? “procc”? use something more semantically relevant when you can: &action &event &what\_i\_do\_on\_wednesdays T. ---
**Author:** ![S-gw](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/ed655f/32.png) [@S-gw](https://www.ruby-forum.com/u/S-gw)\ **Post date:** [November 15, 2007, 11:40am UTC](https://www.ruby-forum.com/t/prock-not-block/120237/3 "2007-11-15T11:40:37Z")
On Nov 14, 2007, at 17:28 , Greg W. wrote: > In all of the code below, “prock” by itself is always a proc, while > the > combination “&prock” is always a block: Class doesn’t matter, methods do. I’m (almost) always passing in a block, so its a block. ---
**Author:** ![S-gw](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/ed655f/32.png) [@S-gw](https://www.ruby-forum.com/u/S-gw)\ **Post date:** [November 15, 2007, 9:34pm UTC](https://www.ruby-forum.com/t/prock-not-block/120237/4 "2007-11-15T21:34:14Z")
Trans wrote: > use something more semantically relevant when you can: > > &action > &event > &what\_i\_do\_on\_wednesdays Certainly, in real-life code. I was thinking of examples in textbooks where the reader is trying to sort out the difference between blocks and procs. In these examples, I’ve seen the variable “block” used – eg, in “Block, Closures, and Proc Objects” in “The Ruby Language” in Pickaxe – and I find it unappealing to remind myself that “block” is a proc, and “&block” is a block. ---
**Author:** ![S-gw](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/ed655f/32.png) [@S-gw](https://www.ruby-forum.com/u/S-gw)\ **Post date:** [November 15, 2007, 10:06pm UTC](https://www.ruby-forum.com/t/prock-not-block/120237/5 "2007-11-15T22:06:56Z")
Eric H. wrote: > Class doesn’t matter, methods do. You’re preaching to the choir 🙂 > I’m (almost) always passing in a block, so its a block. If you’re passing in a block, then the method parameter is something like “&foo”. If you’re passing in a proc, then the message parameter is something like “foo”. In either case, in the method body, “&foo” is a block, and “foo” is a proc. It may be that “&foo” is pedagogically described as the “foo” parameter with an “&” modifier. But that is misleading. The block argument is bound to “&foo”, not to “foo”. And the block argument is accessible in the method body – as “&foo”. So in all cases, “&foo” is a block iff “foo” is a proc. ---
**Author:** ![S-gw](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/ed655f/32.png) [@S-gw](https://www.ruby-forum.com/u/S-gw)\ **Post date:** [November 16, 2007, 10:20am UTC](https://www.ruby-forum.com/t/prock-not-block/120237/6 "2007-11-16T10:20:22Z")
On Nov 15, 2007, at 13:06 , Greg W. wrote: > Eric H. wrote: > > > Class doesn’t matter, methods do. > > You’re preaching to the choir 🙂 > > > I’m (almost) always passing in a block, so its a block. > > If you’re passing in a block, then the method parameter is something > like “&foo”. You can’t make a variable &foo. def x(&foo); end Says that if you pass in a block, assign it to the foo variable. mything = … x(&mything) Says call mything.to\_proc and pass that result as a block to #x. If you see & used outside of those two contexts, it is the & method. > If you’re passing in a proc, then the message parameter is > something like “foo”. In either case, in the method body, “&foo” > is a block, and “foo” is a proc. Class and type don’t matter, methods do. If I call x(&5), Ruby will call 5.to\_proc for me and pass the result of that along. If I try to use &foo as a variable, ruby gives a syntax error. You can only use &foo for describing a method argument, or for passing an argument to a method. > It may be that “&foo” is pedagogically described as the “foo” > parameter > with an “&” modifier. But that is misleading. This is correct, and this is what happens. Its not misleading. &foo works the same as \*foo. If I put \*foo in the method signature, all the arguments will be collected into foo as an Array, like &foo collects a block into foo as a Proc. If I call a method and use \*foo as one of the parameters, Ruby will call foo.to\_ary and pass the results to the method like &foo calls foo.to\_proc. Both \*foo and &foo are optional. You won’t get an ArgumentError if you omit an item with \*foo or a block with &foo. If \* is the “splat” operator, & is the “block splat” (“blockify”?) operator. > The block argument is bound to “&foo”, not to “foo”. And the block > argument is accessible in the method body – as “&foo”. No, it is bound too foo, not &foo. &foo is not a variable name. > So in all cases, “&foo” is a block iff “foo” is a proc. def z(&foo) p foo end z() # =\> nil ---
**Author:** ![S-gw](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/ed655f/32.png) [@S-gw](https://www.ruby-forum.com/u/S-gw)\ **Post date:** [November 17, 2007, 4:20am UTC](https://www.ruby-forum.com/t/prock-not-block/120237/7 "2007-11-17T04:20:28Z")
On Nov 16, 2007, at 02:01 , Greg W. wrote: > not. If you want to use the _block_ argument in the method body, you > use the expression &foo, not foo. If by ‘use the block argument in the method body’ you mean ‘call methods on the block argument’, you must use ‘foo’, as ‘&foo.some\_method’ is a syntax error. If by ‘use […]’ you mean ‘pass foo as a block argument to another method’ (like the array- splat \* syntax) you are correct. > foo is a proc; &foo – an expression, not a parameter as I > erroneously said – is a block. &foo is not an expression, & can only be used to modify argument passing: $ ruby def x(&foo) &foo end -:1: parse error def x(&foo) &foo end ^ def x(&foo) (&foo) end -:2: parse error def x(&foo) (&foo) end ^ ---
**Author:** ![S-gw](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/ed655f/32.png) [@S-gw](https://www.ruby-forum.com/u/S-gw)\ **Post date:** [November 16, 2007, 11:01am UTC](https://www.ruby-forum.com/t/prock-not-block/120237/8 "2007-11-16T11:01:41Z")
Eric H. wrote: > > It may be that “&foo” is pedagogically described as the “foo” > > parameter with an “&” modifier. But that is misleading. > > This is correct, and this is what happens. Its not misleading. I take your point. Thanks for the correction. Nevertheless, even though the argument is a block, the parameter foo is not. If you want to use the _block_ argument in the method body, you use the expression &foo, not foo. foo is a proc; &foo – an expression, not a parameter as I erroneously said – is a block. > def z(&foo) > p foo > end > > z() # =\> nil Because no block was supplied.