Another Q: find behavior

[Krekna Mektek]

Hi,

Still learning from the Pickaxe book, and I've got a question about this code:

class Array
def find
for i in 0..size
value = self
puts self
return value if yield(value)
end
return nil
end
end

[1,3,5,7,9].find {|v| v*v > 30 }

irb(main):369:0> [1,3,5,7,9].find {|v| v*v > 30 }
=> 7


how come it prints only 7, and not also 9?
The loop is not stopping as far as I can see, and 9 times 9 is also
bigger then 30.

Krekna

 

[Morton Goldberg]

Hi,

Still learning from the Pickaxe book, and I've got a question about
this code:

class Array
def find
for i in 0..size
value = self
puts self
return value if yield(value)
end
return nil
end
end

[1,3,5,7,9].find {|v| v*v > 30 }

irb(main):369:0> [1,3,5,7,9].find {|v| v*v > 30 }
=> 7


how come it prints only 7, and not also 9?
The loop is not stopping as far as I can see, and 9 times 9 is also
bigger then 30.

But the loop does stop when it reaches 7. As soon as 'yield(value)'
evaluates to true, the 'return' is executed and both the method and
the loop terminate.

Regards, Morton

 

[Krekna Mektek]

Ah, so the return exits the loop, now I understand.

@Joey:
What I want to achieve? This is just an example from the book

Krekna

Hi,

Still learning from the Pickaxe book, and I've got a question about
this code:

class Array
def find
for i in 0..size
value = self
puts self
return value if yield(value)
end
return nil
end
end

[1,3,5,7,9].find {|v| v*v > 30 }

irb(main):369:0> [1,3,5,7,9].find {|v| v*v > 30 }
=> 7


how come it prints only 7, and not also 9?
The loop is not stopping as far as I can see, and 9 times 9 is also
bigger then 30.

But the loop does stop when it reaches 7. As soon as 'yield(value)'
evaluates to true, the 'return' is executed and both the method and
the loop terminate.

Regards, Morton

 

[Robert Klemme]

Hi,

Still learning from the Pickaxe book, and I've got a question about this
code:

class Array
def find
for i in 0..size

That line should read

for i in 0...size

Otherwise you will always throw nil at your test if it failed for all
elements in the array.

value = self
puts self
return value if yield(value)
end
return nil
end
end

[1,3,5,7,9].find {|v| v*v > 30 }

irb(main):369:0> [1,3,5,7,9].find {|v| v*v > 30 }
=> 7


how come it prints only 7, and not also 9?

Because the "return" will immediately make the method exit.

The loop is not stopping as far as I can see, and 9 times 9 is also
bigger then 30.

The loop will stop once the first match is found precisely because of
the "return". Either you tested a different piece of code than you
posted or you overlooked something.

Kind regards

robert