Succ distance between two strings

[trans. (T. Onoma)]

Is there an efficient way to calculate the "succ distance" between two strings
(without iterating over each succession)? Examples:

'a'..'a' 0
'a'..'b' 1
'a'..'z' 25
'a'..'aa' 26

T.

 

[David A. Black]

Hi --

Is there an efficient way to calculate the "succ distance" between two strings
(without iterating over each succession)? Examples:

'a'..'a' 0
'a'..'b' 1
'a'..'z' 25
'a'..'aa' 26

'a'...'aa'.to_a.size # would be one way


David

 

[(Curne) Simon Conrad-Armes]

Hi --



'a'...'aa'.to_a.size # would be one way

That still iterates over all elements but it looks sweet
Only for large strings would be a problem


My stab:

def diff_succ s1, s2
t1 = t2 = 0
s1.each_byte{|c| t1 = t1*26 + c - 96}
s2.each_byte{|c| t2 = t2*26 + c - 96}
t2 - t1
end

def t s1, s2
puts "#{s1}..#{s2} => #{diff_succ s1, s2}"
end

t 'a', 'a' #0
t 'a', 'b' #1
t 'a', 'z' #25
t 'a', 'aa' #26

t 'A', 'B'
t 'A', 'Z'
t 'A', 'AA'


output:
a..a => 0
a..b => 1
a..z => 25
a..aa => 26
A..B => 1
A..Z => 25
A..AA => -806


Notice how it breaks on multi-letter uppercase strings? that is because
of the -96. Maybe one should just lowercase the args...

/Curne

 

[Chad Fowler]

Hi --





'a'...'aa'.to_a.size # would be one way

For the first 3 examples you can also treat them as characters and do:

?a - ?a #=> 0
?b - ?a #=> 1
?z - ?a #=> 25

Not exactly what you want though.

Chad Fowler
http://chadfowler.com
http://rubycentral.org
http://rubygarden.org
http://rubygems.rubyforge.org (over 20,000 gems served!)

 

[gabriele renzi]

trans. (T. Onoma) ha scritto:

Is there an efficient way to calculate the "succ distance" between two strings
(without iterating over each succession)? Examples:

'a'..'a' 0
'a'..'b' 1
'a'..'z' 25
'a'..'aa' 26

T.

my tentativ impl would be
class String
def value
i=-26
split(//).inject(0){|x,y|
i+=26
x+y[0]-?a+i
}
end
end

class Range
def dist
max.value - min.value
end
end
p 'aa'.value - 'a'.value
p 'a'.value - 'a'.value
p ('a'..'b').dist
p ('a'..'z').dist

note that '-?a' could be moved in the 'i' initialization but I'm running
away

 

[trans. (T. Onoma)]

Thanks all for the responses. Looks like it _might_ be doable, but the
complexity quickly racks up. The presented quick stabs at it fail on capital
letters and other characters.

Running away might be the best course of action

T.

| > Is there an efficient way to calculate the "succ distance" between two
| > strings (without iterating over each succession)? Examples:
| >
| > 'a'..'a' 0
| > 'a'..'b' 1
| > 'a'..'z' 25
| > 'a'..'aa' 26
| >
| > T.
|
| my tentativ impl would be
| class String
| def value
| i=-26
| split(//).inject(0){|x,y|
| i+=26
| x+y[0]-?a+i
| }
| end
| end
|
| class Range
| def dist
| max.value - min.value
| end
| end
| p 'aa'.value - 'a'.value
| p 'a'.value - 'a'.value
| p ('a'..'b').dist
| p ('a'..'z').dist
|
| note that '-?a' could be moved in the 'i' initialization but I'm running
| away

--
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// trans.
/ \ (e-mail address removed)

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-Tadayoshi Funaba

 

[Brian Schröder]

Hi --



'a'...'aa'.to_a.size # would be one way

That does not work, as the ... have a very low binding. It seems a common error I made often.

bschroed@black:~ $ irb
irb(main):001:0> 'a'...'aa'.to_a.size
=> "a"...1
irb(main):002:0> ('a'...'aa').to_a.size
=> 26

Regards,

Brian

 

[David A. Black]

Hi --

That does not work, as the ... have a very low binding. It seems a common error I made often.

bschroed@black:~ $ irb
irb(main):001:0> 'a'...'aa'.to_a.size
=> "a"...1
irb(main):002:0> ('a'...'aa').to_a.size
=> 26

Whoops -- I did actually do it correctly in irb, to make sure, and
then wrote it out wrongly instead of pasting it.

It's like putting (i.e., putt-ing, in golf) -- you can never take it
for granted


David