I keep getting a 'no block given' error when trying to pass the string to the is_tut? method. I am new to Ruby and have no idea what I'm doing wrong. Any and all help would be appreciated.
class Tut
##consonants = ["b","c","d","f","g","h","j","k","l","m","n","p","q","r","s","t","v","w","x","y","z"]
def is_tut? string
if string =~ /^(([b-df-hj-np-z]ut)|([aeiou\s])|[[:punct:]])+$/i
yield
else
false
end
end
def self.to_tut string
string.each_char do |c|
c += "ut" if ##consonants.find { |i| i == c.downcase }
yield c
end
end
def self.to_english string
array = string.split //
array.each do |c|
if ##consonants.find { |i| i == c.downcase }
array.shift
array.shift
end
yield c
end
end
end
#Tut.to_tut( "Wow! Look at this get converted to Tut!" ) { |c| print c }
# should output : Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!
puts
puts
tut = Tut.to_tut( "Wow! Look at this get converted to Tut!" )
puts "from return: #{tut}"
puts
#Tut.to_tut( "Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!" ) { |c| print c }
# should outout : Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!
puts
puts
#tut = Tut.to_tut( "Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!" )
#puts "from return: #{tut}"
puts
#tut_string = ""
#Tut.to_tut( "I'm in tut but I want to be in english." ) { |c| tut_string += c }
#puts tut_string
# should output : I'mut inut tututut bututut I wutanuttut tuto bute inut enutgutlutisuthut.
puts
#Tut.to_english( tut_string ) { |c| print c }
# should output : I'm in tut but I want to be in english.
If you have yield within your method definition, that means you have to obligatorily pass a block when you use it (unless the part including it is not executed according to conditioning etc.). (You might already know, but in case you don't: a block is something that is described as {...} or do ... end) And yield will refer to the block.
If you want to make a block optional, then one way to do it is to put the & symbol before the variable name.
def method(argument, &block_argument)
if block_argument # block is given
block_argument.call(argument_for_block) # use call to execute the block
else # the value of block_argument becomes nil if you didn't give a block
# block was not given
end
end
This will allow optional block. Or, as suggested by Squeegy,
def method(argument)
if block_given? # block is given
yield(argument_for_block) # no need to use call to execute the block
else
# block was not given
end
end
will also work.
Because you're calling yield in your to_tut() method, this line will fail:
tut = Tut.to_tut( "Wow! Look at this get converted to Tut!" )
You either need to give a block (as you did in the first commented-out call to Tut.to_tut()), or you need to modify your to_tut() function to make the code block optional:
def self.to_tut string
string.each_char do |c|
c += "ut" if ##consonants.find { |i| i == c.downcase }
yield c if block_given?
end
end
yield requires a block to be passed to to_tut.
When you do:
Tut.to_tut( "Wow! Look at this get converted to Tut!" ) { |c| print c }
It works because it has the block { |c| print c }.
Without a block it will raise the error.
Related
This is really driving me up a wall.
I have an instance method I'm trying to debug, but I'm running into an issue where my puts and gets aren't showing up inside the instance method.
Code:
#! /usr/bin/env ruby
class Calculator
def evaluate(string)
ops = string.split(' ')
ops.map! do |item|
if item.is_a? Numeric
return item.to_i
else
return item.to_sym
end
end
puts "Got #{string}" #Doesn't output
puts "Converted to #{ops}" #This too
opscopy = ops.clone
ops.each.with_index do |item, index|
if item == :* || item == :/
opscopy[index] = ops[index-1].send(item, ops[index+1])
opscopy[index-1] = opscopy[index+1] = nil
end
end
ops = opscopy.compact
puts "After multi/div #{ops}"
ops.each.with_index do |item, index|
if item == :+ || item == :-
opscopy[index] = ops[index-1].send(item, ops[index+1])
opscopy[index-1] = opscopy[index+1] = nil
end
end
puts "After +/- #{opscopy.compact}"
opscopy.compact.first
end
end
item = Calculator.new.evaluate "4 * 2"
puts "#{item} == 8" #Prints :(
Output:
action#X:~/workspace/ruby$ ./calculator.rb
4 == 8
That return in your map! block is where the problem is.
ops.map! do |item|
if item.is_a? Numeric
return item.to_i # returns from method
else
return item.to_sym # returns from method
end
end
You are returning the method in your map! block before the puts is called.
Change the map! block to:
ops.map! do |item|
item.send(item.is_a?(Numeric) ? :to_i : :to_sym)
end
str = 'put returns between paragraph put returns between paragraph put returns between paragraph'
def word_count(string)
resut= []
return result = string.split.inject(Hash.new(0)) { |h,v| h[v] += 1; h }
end
def parse_word(word)
word.gsub!(/[^a-zA-Z0-9]/, " ")
word.downcase!
#yoo= word
end
result =word_count(str)
print result, "\n\n"
res2 = result.select { |pair| pair[1] > 1 } `#Error coming`
I am getting OutPut
**
OutPut
**
{"put"=>3, "returns"=>3, "between"=>3, "paragraph"=>3}
I need OutPut Like this
**
OutPut
**
{"put"=>3, "returns"=>3, "between"=>3, "paragraph"=>3}
and
put: 3
returns: 3
between: 3
but the main problem is that he gave us the code to do that but i cant able to understand it
I am not getting this what this code will do can anyone help me ...And modify it so it can work
The following processes the first paragraph of put returns ... Note that ss is an array of those words that occur at least twice in this paragraph.
nect = ss.select { |p| p[1] > 1 }
nect .sort.each do |key, count|
puts "#{key}: #{count}"
end
module WordCount
def self.word_count(s)
count_frequency(words_from_string(s))
end
def self.word_count_from_file(filename)
s = File.open(filename) { |file| file.read }
word_count(s)
end
def self.words_from_string(s)
s.downcase.scan(/[\w']+/)
end
def self.count_frequency(words)
counts = Hash.new(0)
for word in words
counts[word] += 1
end
# counts.to_a.sort {|a,b| b[1] <=> a[1]}
# sort by decreasing count, then lexicographically
counts.to_a.sort do |a,b|
[b[1],a[0]] <=> [a[1],b[0]]
end
end
end
def word_count(s)
WordCount.word_count(s)
end
I am trying to create a program where by the user can enter multiple names. those names are then displayed under each other in alphabetical order, and print(display) every second name backwards. i have gone through several tutorials this is my second day using ruby.. here is what i have so far.
name_list = {}
puts 'please enter names seperated by a space:'
name_list = gets.chomp
names = name_list.split(" ")
to grab names...
names.sort do |a,b| a.upcase <=> b.upcase end
display = "#{names}"
for ss in 0...display.length
print ss, ": ", display[ss], "\n"
end
to arrange them alphabetically and under each other.
i am really struggling to mesh it all together i think i have got at least half a dozen errors in here...if i am on the wrong path could someone guide me to some info so i can start again??
EDIT
i also had this idea of using a class.
but i would have to program the names in i wanted the user to be able to add info via the consol.
class A
def initialize(name)
#name = name
end
def to_s
#name.reverse
end
end
>> a = [A.new("greg"),A.new("pete"),A.new("paul")]
>> puts a
Problems in your code:
name_list defined as an empty hash at the top but not used.
split(" ") -> split
sort { |a, b| a.method <=> b.method } -> sort_by { |x| x.method } -> sort_by(&:method)
sort is not an in-place operation, assign the result (or directly use it).
display = "#{names}" -> display = names
for ss in 0...display.length -> enumerable.each_with_index { |item, index| ... }
don't write do/end in one-liners, use { ... }
I'd write:
puts 'Please enter names separated by spaces'
gets.split.sort_by(&:upcase).each_with_index do |name, index|
puts "%s: %s" % [index, (index % 2).zero? ? name : name.reverse]
end
A few pointers then:
names.sort do |a,b| a.upcase <=> b.upcase end # Will not modify the "names" array, but will return a sorted array.
names.sort! do |a,b| a.upcase <=> b.upcase end # Will modify the "names" array.
To display your names:
names.each_with_index do |name, index|
if index % 2 == 0
puts name
else
puts name.reverse
end
end
puts 'please enter names seperated by a space`enter code here` :'
names = gets.chomp.split(" ")
names.sort! {|a,b| a.upcase <=> b.upcase } # For a single line use {..} instead of do..end
names.each_with_index do |n,i|
if i % 2 == 0
p n
else
p n.reverse
end
end
You can also use a ternary operator, I used the full if else block for readability in this case.
names.each_with_index do |n,i|
p (i % 2 == 0) ? n : n.reverse
end
EDIT
command = ""
names = []
while command != "exit"
puts 'please enter names seperated by a space`enter code here` :'
command = gets.chomp!
if command == "display"
names.sort! {|a,b| a.upcase <=> b.upcase } # For a single line use {..} instead of do..end
names.each_with_index do |n,i|
if i % 2 == 0
p n
else
p n.reverse
end
end
else
names << command
end
end
I am trying to make this code return when called without a block. The uncommented lines at the bottom is what I'm trying to get to return. The first uncommented line should return in tut, second line converted to english and the last should be in english. And why is the line " puts eng " returning up and down and not in sentence form? Thanks for any and all help.
Here's my code:
class Tut
##consonants = ["b","c","d","f","g","h","j","k","l","m","n","p","q","r","s","t","v","w","x","y","z"]
def is_tut? string
if string =~ /^(([b-df-hj-np-z]ut)|([aeiou\s])|[[:punct:]])+$/i
yield
else
false
end
end
def self.to_tut string
string.each_char do |c|
c += "ut" if ##consonants.find { |i| i == c.downcase }
yield c if block_given?
end
end
def self.to_english string
array = string.split //
array.each do |c|
if ##consonants.find { |i| i == c.downcase }
array.shift
array.shift
end
yield c if block_given?
end
end
end
#Tut.to_tut( "Wow! Look at this get converted to Tut!" ) { |c| print c }
# should output : Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!
#puts
#puts
tut = Tut.to_tut( "Wow! Look at this get converted to Tut!" )
puts "from return: #{tut}"
puts
#Tut.to_tut( "Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!" ) { |c| print c }
#should outout : Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!
#puts
#puts
tut = Tut.to_tut( "Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!" )
puts "from return: #{tut}"
#puts
#tut_string = ""
#Tut.to_tut( "I'm in tut but I want to be in english." ) { |c| tut_string += c }
#puts tut_string
# should output : I'mut inut tututut bututut I wutanuttut tuto bute inut enutgutlutisuthut.
puts
#Tut.to_english( tut_string ){ |c| print c }
# should output : I'm in tut but I want to be in english.
lan = Tut.to_english( tut )
puts lan
(Opening note: You normally don't want to modify an Enumerable object while iterating over it, since that makes it much harder to read the code and debug it.)
Your to_tut doesn't retain your modifications because the "c" block variable is a copy of the string slice, instead of a reference to part of the string (if it were a ref, you'd be able to use << to append; "+=" still wouldn't work because it reassigns rather than changing the ref). That's just how each_char works, since a String doesn't contain references.
If you wanted to modify the string in place, you'd probably have to count backwards and then insert the 'ut' by index via string#[]= . But that's way complicated so I'll present a couple alternates.
Working to_tut #1:
def self.to_tut string
string.chars.map do |c|
yield c if block_given?
# this must be the last expression the block
if ##consonants.find { |i| i == c.downcase }
c + 'ut'
else
c
end
end.join
end
Working to_tut #2 - this is probably the most ruby-ish way to do it:
def self.to_tut string
string.gsub(/[#{##consonants.join}]/i) {|match|
yield match if block_given?
# this must be the last expression in the block
match + 'ut'
}
end
Your to_english doesn't work because array.shift always removes the first element of the array. Instead, you want to track the current index, and remove 2 chars starting from index+1.
Working to_english:
def self.to_english2 string
array = string.split //
array.each_with_index do |c, idx|
if ##consonants.find { |i| i == c.downcase }
array.slice!(idx+1, 2)
end
yield c if block_given?
end
array.join
end
Regarding why your "puts lan" returns one char per line - it's because your to_english returns an array. You'll want to call join to convert it.
The methods to_tut and to_english are giving you wrong answers when used without a block. This happens because ruby always returns the last value evaluated in your method. In your code that will be the result of the string.each_char for to_tut or array.each for to_english. In both cases, the result contains the original input, which is consequently returned and printed.
As to the puts eng, it prints the array returned by array.each of to_english.
def get_type
x = [{:type=>'A', :patterns=>['foo.*']}, {:type=>'B', :patterns=>['bar.*']}]
name = 'foo.txt'
result = x.each { |item|
item[:patterns].each { |regex|
puts "Checking #{regex} against #{name}"
if !name.match(regex).nil?
puts "Found match: #{item[:type]}"
return item[:type]
end
}
}
end
result = get_type
puts "result: #{result}"
Expected output:
Checking foo.* against foo.txt
Found match: A
result: A
However, all I see is:
Checking foo.* against foo.txt
Found match: A
My current work around is this:
def get_type
x = [{:type=>'A', :patterns=>['foo.*']}, {:type=>'B', :patterns=>['bar.*']}]
name = 'foo.txt'
result = []
x.each { |item|
item[:patterns].each { |regex|
puts "Checking #{regex} against #{name}"
if !name.match(regex).nil?
puts "Found match: #{item[:type]}"
result << item[:type]
end
}
}
result[0] unless result.empty?
end
Why doesn't the first approach work? or maybe it is 'working', I just don't understand why I'm not getting what I'd expect.
May I suggest a refactor? your code looks kind of clunky because you are using each loops (imperative) when you in fact need a map+first (functional). As Ruby enumerables are not lazy this would be inefficient, so people usually build the abstraction Enumerable#map_detect (or find_yield, or find_first, or map_first):
def get_type_using_map_detect(name)
xs = [{:type => 'A', :patterns => ['foo.*']}, {:type => 'B', :patterns => ['bar.*']}]
xs.map_detect do |item|
item[:patterns].map_detect do |regex|
item[:type] if name.match(regex)
end
end
end
This is a possible implementation of the method:
module Enumerable
# Like Enumerable#map but return only the first non-nil value
def map_detect
self.each do |item|
if result = (yield item)
return result
end
end
nil
end
end
Works fine for me. Are you actually invoking it with
result = get_type puts "result: #{result}"
? Because that shouldn't work at all, though I'm assuming there's a linefeed that got eaten when you posted this.