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12/3/2007 11:59:00 AM
Note: parts of this message were removed by the gateway to make it a legal Usenet post.
This is my solution:
# this program understands simple operations and also sin, cos, tg and ctg
# to use, provide string in BPN as argument
# example: ruby postf2inf '3 5 + sin 5 3 cos + /'
# result in "sin(3 + 5) / (5 + cos(3))"
str_postf=ARGV[0]
str_inf=[]
prior = {'+'=>1,'-'=>1,'*'=>3,'/'=>3}
stack = str_postf.split(' ')
0.upto stack.size-1 do |l|
if ['+','-','*','/'].include?(stack[l])
arg1 = str_inf.pop
arg2 = str_inf.pop
arg1[1]='('+arg1[1]+')' if arg1[0]<prior[stack[l]]
arg2[1]='('+arg2[1]+')' if arg2[0]<prior[stack[l]]
str_inf.push([prior[stack[l]] , arg2[1]+" #{stack[l]} "+arg1[1]])
elsif ['sin','cos','tg','ctg'].include?(stack[l])
str_inf.push([5 , "#{stack[l]}(#{str_inf.pop[1]})"])
else
str_inf.push([5,stack[l]])
end
end
p str_inf.pop[1]