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Pascal's triangle: Difference between revisions
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makeCommand("yourFavoriteWebBrowser")("triangle.html")</lang>
=={{header|Eiffel}}==
<lang eiffel>
note
description : "Prints pascal's triangle"
computer_arithmetic :
"[
This version avoids integer overflow and stops at the last representable number in the sequence.
]"
output : "[
Per requirements of the RosettaCode example, execution will print the first n rows of pascal's triangle
]"
date : "19 December 2013"
authors : "Sandro Meier", "Roman Brunner"
revision : "1.0"
libraries : "Relies on HASH_TABLE from EIFFEL_BASE library"
implementation : "[
Recursive implementation to calculate the n'th row.
]"
warning : "[
Will not work for large n's (INTEGER_32)
]"
class
APPLICATION
inherit
ARGUMENTS
create
make
feature {NONE} -- Initialization
make
local
n:INTEGER
do
create {HASH_TABLE[ARRAY[INTEGER],INTEGER]}pascal_lines.make (n) --create the hash_table object
io.new_line
n:=25
draw(n)
end
feature
line(n:INTEGER):ARRAY[INTEGER]
--Calculates the n'th line
local
upper_line:ARRAY[INTEGER]
i:INTEGER
do
if n=1 then --trivial case first line
create Result.make_filled (0, 1, n+2)
Result.put (0, 1)
Result.put (1, 2)
Result.put (0, 3)
elseif pascal_lines.has (n) then --checks if the result was already calculated
Result := pascal_lines.at (n)
else --calculates the n'th line recursively
create Result.make_filled(0,1,n+2) --for caluclation purposes add a 0 at the beginning of each line
Result.put (0, 1)
upper_line:=line(n-1)
from
i:=1
until
i>upper_line.count-1
loop
Result.put(upper_line[i]+upper_line[i+1],i+1)
i:=i+1
end
Result.put (0, n+2) --for caluclation purposes add a 0 at the end of each line
pascal_lines.put (Result, n)
end
end
draw(n:INTEGER)
--draw n lines of pascal's triangle
local
space_string:STRING
width, i:INTEGER
do
space_string:=" " --question of design: add space_string at the beginning of each line
width:=line(n).count
space_string.multiply (width)
from
i:=1
until
i>n
loop
space_string.remove_tail (1)
io.put_string (space_string)
across line(i) as c
loop
if
c.item/=0
then
io.put_string (c.item.out+" ")
end
end
io.new_line
i:=i+1
end
end
feature --Access
pascal_lines:HASH_TABLE[ARRAY[INTEGER],INTEGER]
--Contains all already calculated lines
end
</lang>
=={{header|Erlang}}==
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