Closures syntax?


#1

Hi, im new to ruby. I ve qaquestions about closures

  1. if i defiene this

def loopN n, &b
i=0
while (i<n) do
b.call
i+=1
end
end

Why the first and the second calls dosnt works and the third works?
1.1) loopN 5, {puts “hola”} # compile error , parse error unexpected
“{”, expected “$”
1.2) loopN 5 {puts “hola”} # compile error , unexpected tString.
1.2) loopN (5) {puts “hola”} # works

thanks


Pedro Del G.

Email : removed_email_address@domain.invalid


#2

Hi,
Am Donnerstag, 15. Feb 2007, 20:52:08 +0900 schrieb Pedro Del G.:

Why the first and the second calls dosnt works and the third works?
1.1) loopN 5, {puts “hola”} # compile error , parse error unexpected
“{”, expected “$”
1.2) loopN 5 {puts “hola”} # compile error , unexpected tString.
1.2) loopN (5) {puts “hola”} # works

Precedence. “do … end” has low precedence, applies to the leftmost
function name, “{ …}” has high.

loopN 5 do puts “hola” end # should work

Bertram


#3

On Feb 15, 2007, at 6:52 AM, Pedro Del G. wrote:

Why the first and the second calls dosnt works and the third works?
1.1) loopN 5, {puts “hola”} # compile error , parse error unexpected
“{”, expected “$”

Ruby doesn’t expect a comma between the last standard argument and
the optional block argument. Drop the comma.

1.2) loopN 5 {puts “hola”} # compile error , unexpected tString.

The {} of the block is binding to the number 5, which is a syntax error.
You need to add parens to clarify your intent as in:

1.2) loopN (5) {puts “hola”} # works

This would be more commonly written as:

loopN(5) { puts “hola”}

Alternatively you can use do/end, which has low precedence

loopN 5 do
puts “hola”
end

Gary W.