Asp Forum - symbol tricks - comp.lang.ruby

YAD

9/7/2006 5:36:00 PM

Trying to write one function that will find a
full row or column in a 2D array (for tic-tac-toe).
Like this:

------------------------------------------
$grid =
[[' ',' ','O'],
['X','X','X'],
['O',' ',' ']]

def doAxis (outr,inr)
outerLoop:
[0,1,2].each do |:"#{outr}"|
[0,1,2].each do |:"#{inr}"|
if ($grid[row][col] != 'X')
next outerLoop # is this supported?
end
end
puts "Got 3 in a row!"
return true
end
false
end

doAxis 'row', 'col' # want to find full rows
doAxis 'col', 'row' # want to find full columns
-----------------------------------------------

Is this possible? So far Ruby doesn't seem to like it.
What are the limits to how you can use this construction?

:"#{foo}"

--
Yet another Dan

23 Answers

Jason Nordwick

9/7/2006 6:05:00 PM

I don't think you can use a symbol in a parameter list ever.

-j

(grid+grid.transpose).map {|x,y,z| x=='X' && x==y && y==z}

As long as you don't want diagonals

YAD wrote:
> Trying to write one function that will find a
> full row or column in a 2D array (for tic-tac-toe).
> Like this:
>
> ------------------------------------------
> $grid =
> [[' ',' ','O'],
> ['X','X','X'],
> ['O',' ',' ']]
>
> def doAxis (outr,inr)
> outerLoop:
> [0,1,2].each do |:"#{outr}"|
> [0,1,2].each do |:"#{inr}"|
> if ($grid[row][col] != 'X')
> next outerLoop # is this supported?
> end
> end
> puts "Got 3 in a row!"
> return true
> end
> false
> end
>
> doAxis 'row', 'col' # want to find full rows
> doAxis 'col', 'row' # want to find full columns
> -----------------------------------------------
>
> Is this possible? So far Ruby doesn't seem to like it.
> What are the limits to how you can use this construction?
>
> :"#{foo}"
>

Paul Lutus

9/7/2006 6:22:00 PM

YAD wrote:

> Trying to write one function that will find a
> full row or column in a 2D array (for tic-tac-toe).

I'm making an assumption here, that you want to find a winning pattern.

----------------------------------------------------------

#! /usr/bin/ruby

grid =
[
['X',' ','O'],
[' ','O',' '],
['O',' ','X']
]

def test_rows(array)
array.each do |row|
return row.first if (row.first != ' ' && row.uniq.size == 1)
end
return false
end

def test_diagonals(array)
c = array[1][1]
if(c != ' ')
return c if((c == array[0][2] && c == array[2][0]) || (c == array[0][0] && c == array[2][2]))
end
return false
end

def find_winner(array)
w = test_rows(array) || test_rows(array.transpose) || test_diagonals(array)
puts "found winning row for player \"#{w}\"" if w
end

find_winner(grid)

Output: found winning row for player "O"

--
Paul Lutus
http://www.ara...

Johannes Held

9/7/2006 6:30:00 PM

Paul Lutus schrieb:
> I'm making an assumption here, that you want to find a winning pattern.
> snipped the code
> Output: found winning row for player "O"
That's an elegant solution without "black magic".

--
GruÃ?, Johannes
http://www...
http://gallery.he...

Paul Lutus

9/7/2006 6:54:00 PM

Johannes Held wrote:

> Paul Lutus schrieb:
>> I'm making an assumption here, that you want to find a winning pattern.
>> snipped the code
>> Output: found winning row for player "O"
> That's an elegant solution without "black magic".

Thanks, you are very kind. I personally think my diagonal finder is rather
like squeezing blood from a stone. I suspect someone will think of a more
elegant solution that remains human-readable.

Thanks again. :)

--
Paul Lutus
http://www.ara...

YAD

9/8/2006 12:23:00 AM

Jason Nordwick wrote:
> I don't think you can use a symbol in a parameter list ever.
Thanks. I just wanted to make sure.

> (grid+grid.transpose)
Is this correct Ruby? If so, is it documented online somewhere?
You're not really adding the arrays, are you?

Also, transpose sounds like the simplest solution.

--
Yet another Dan

YAD

9/8/2006 1:15:00 AM

Paul Lutus wrote:
> I'm making an assumption here, that you want to find a winning pattern.
I want to calculate several things (at different times), including
whether a player has two in a row, and whether a player has two blank
squares that will win the game (two pairs in a row that require
different squares to be completed).
Since that's a total of six functions, I figured combining rows & cols
into one function would be the simplest way to reduce the total amount
of code.

> def find_winner(array)
> w = test_rows(array) > || test_rows(array.transpose) > || test_diagonals(array)

This looks like the simplest way to do it. The only concern I would
have with this solution is performance in searching a whole tree of
possible future grids.

--
Yet another Dan

Paul Lutus

9/8/2006 1:49:00 AM

YAD wrote:

> Paul Lutus wrote:
>> I'm making an assumption here, that you want to find a winning pattern.
> I want to calculate several things (at different times), including
> whether a player has two in a row, and whether a player has two blank
> squares that will win the game (two pairs in a row that require
> different squares to be completed).
> Since that's a total of six functions, I figured combining rows & cols
> into one function would be the simplest way to reduce the total amount
> of code.

If speed is your primary goal (referring to later content in your post),
then minimizing the number of functions may not be so important.

>> def find_winner(array)
>> w = test_rows(array) >> || test_rows(array.transpose) >> || test_diagonals(array)
>
> This looks like the simplest way to do it. The only concern I would
> have with this solution is performance in searching a whole tree of
> possible future grids.

Given the speed requirement, this might be a case where (at risk of sounding
sacrilegious) you would test various approaches in Ruby until you came up
with an obviously efficient method, then converted the algorithm into C or
C++. In this case Ruby would serve as a quick prototyping tool (but a
comparatively slow execution tool).

As to "possible future grids", if you factor out mirror reflections and
transpositions, there really aren't that many unique board configurations
in this game. Compare this to the Japanese game Go, which is still not
well-represented in a computer program.

--
Paul Lutus
http://www.ara...

Jason Nordwick

9/8/2006 3:40:00 PM

YAD wrote:
> Jason Nordwick wrote:
>> (grid+grid.transpose)
> Is this correct Ruby? If so, is it documented online somewhere?
> You're not really adding the arrays, are you?

Plus for arrays and strings is concatenation. I don't like it either, b/c array plus should be addition of corresponding elements, but that is the way things are.

-j

John Miller

9/9/2006 3:41:00 AM

Jason Nordwick wrote:
> YAD wrote:
>> Jason Nordwick wrote:
>>> (grid+grid.transpose)
>> Is this correct Ruby? If so, is it documented online somewhere?
>> You're not really adding the arrays, are you?
>
> Plus for arrays and strings is concatenation. I don't like it either,
> b/c array plus should be addition of corresponding elements, but that is
> the way things are.
>
> -j

No, Vectors should add elemets as they represent mesurable value.
Arrays are part of Set Thoery and as such + most obviously represents
the union of two sets.

This is niether correct nor intuitive:
["red","orange",yellow] + ["green","blue","purple"] =>
["reggreen","orangeblue","yellowpurple] #incorrect!

--
Posted via http://www.ruby-....

Jason Nordwick

9/11/2006 4:12:00 PM

Yes, that's nice. Yet another module with different sematics to learn and more type conversions to do. From learning Ruby, I've learned that there is probably a package to do something. Too bad you also need packages B and C and half a doze type conversion to do any interesting data processing. And this comes from somebody who really wants to like the language, but finds it frustratingly messy.

-j

Steven Lumos wrote:
> Jason Nordwick <jason@adapt.com> writes:
>
>> YAD wrote:
>>> Jason Nordwick wrote:
>>>> (grid+grid.transpose)
>>> Is this correct Ruby? If so, is it documented online somewhere?
>>> You're not really adding the arrays, are you?
>> Plus for arrays and strings is concatenation. I don't like it either, b/c array plus should be addition of corresponding elements, but that is the way things are.
>>
>> -j
>
>>> require 'matrix'
> => true
>>> Vector[1,2,3] + Vector[4,5,6]
> => Vector[5, 7, 9]
>
> Steve
>
>

comp.lang.ruby

symbol tricks

YAD

Jason Nordwick

Paul Lutus

Johannes Held

Paul Lutus

YAD

YAD

Paul Lutus

Jason Nordwick

John Miller

Jason Nordwick

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