I'm playing with Lua https://www.lua.org/pil/1.html and saw the following example.
-- defines a factorial function
function fact (n)
if n == 0 then
return 1
else
return n * fact(n-1)
end
end
print("enter a number:")
a = io.read("*number") -- read a number
print(fact(a))
I was wondering, what is the meaning of "*" in the line a = io.read("*number") -- read a number?
Related
So I need to write a program which gets a table as an input and gives the same table as an output without the values with even keys. So basically I need to filter out the even keys and their values and leave the uneven keys with their values.
local function selecteer_oneven(tabel)
for q, n in ipairs(tabel) do
if (q % 2) == 0 then
table.remove(tabel, q)
end
end
return tabel
end
local function printtabel(tabel)
for k,v in pairs(tabel) do
print(k,v)
end
end
io.write("Geef een lua-tabel: ")
local tabelstring = "t = "..io.read()
local string2tab = loadstring(tabelstring)
string2tab()
local resultaat = selecteer_oneven(t)
printtabel(resultaat)
my input is
{ "aap", "kat", "hond", "paard", "kip", "salamander", "programmeren is leuk" }
and my output is
1 aap
2 hond
3 paard
4 salamander
5 programmeren is leuk
(sorry it is in Dutch)
"Aap", "Hond", "Programmeren is leuk" are the only uneven ones. "paard", and "salamander" are even.
Dont do table.remove on the table you are checking at same time.
Better do a second local table and insert q.
And finaly return the second table...
local function selecteer_oneven(tabel)
local tabel2={}
for q, n in ipairs(tabel) do
if (q % 2) ~= 0 then
table.insert(tabel2, q)
end
end
return tabel2
end
...dont tested - yet ;-)
EDIT: Tested with lua -i
-- <ready>
>function selecteer_oneven(tabel)
local tabel2={}
for q, n in ipairs(tabel) do
if (q % 2) ~= 0 then
table.insert(tabel2, q)
end
end
return tabel2
end
-- <ready>
>dump(selecteer_oneven({1,2,3,4,5,6,7,8,9,10}))
1=1
2=3
3=5
4=7
5=9
-- <ready>
>-- whats dump?
-- <ready>
>code.dump
-- dump()
return function(dump)
for key,value in pairs(dump) do
io.write(string.format("%s=%s\n",key,value))
end
end
-- <ready>
I am new to programming in LUA. And I am not able to solve this question below.
Given a number N, generate a star pattern such that on the first line there are N stars and on the subsequent lines the number of stars decreases by 1.
The pattern generated should have N rows. In every row, every fifth star (*) is replaced with a hash (#). Every row should have the required number of stars (*) and hash (#) symbols.
Sample input and output, where the first line is the number of test cases
This is what I tried.. And I am not able to move further
function generatePattern()
n = tonumber(io.read())
i = n
while(i >= 1)
do
j = 1
while(j<=i)
do
if(j<=i)
then
if(j%5 == 0)
then
print("#");
else
print("*");
end
print(" ");
end
j = j+1;
end
print("\n");
i = i-1;
end
end
tc = tonumber(io.read())
for i=1,tc
do
generatePattern()
end
First, just the stars without hashes. This part is easy:
local function pattern(n)
for i=n,1,-1 do
print(string.rep("*", i))
end
end
To replace each 5th asterisk with a hash, you can extend the expression with the following substitution:
local function pattern(n)
for i=n,1,-1 do
print((string.rep("*", i):gsub("(%*%*%*%*)%*", "%1#")))
end
end
The asterisks in the pattern need to be escaped with a %, since * holds special meaning within Lua patterns.
Note that string.gsub returns 2 values, but they can be truncated to one value by adding an extra set of parentheses, leading to the somewhat awkward-looking form print((..)).
Depending on Lua version the metamethod __index holding rep for repeats...
--- Lua 5.3
n=10
asterisk='*'
print(asterisk:rep(n))
-- puts out: **********
#! /usr/bin/env lua
for n = arg[1], 1, -1 do
local char = ''
while #char < n do
if #char %5 == 4 then char = char ..'#'
else char = char ..'*'
end -- mod 5
end -- #char
print( char )
end -- arg[1]
chmod +x asterisk.lua
./asterisk.lua 15
Please do not follow this answer since it is bad coding style! I would delete it but SO won't let me. See comment and other answers for better solutions.
My Lua print adds newlines to each printout, therefore I concatenate each character in a string and print the concatenated string out afterwards.
function generatePattern()
n = tonumber(io.read())
i = n
while(i >= 1)
do
ouput = ""
j = 1
while(j<=i)
do
if(j%5 == 0)
then
ouput=ouput .. "#";
else
ouput=ouput .. "*";
end
j = j+1;
end
print(ouput);
i = i-1;
end
end
Also this code is just yours minimal transformed to give the correct output. There are plenty of different ways to solve the task, some are faster or more intuitive than others.
I have what I believe is a proper implementation of the miller-rabin algorithm using Lua, and I am trying to get a consistent return for prime numbers. It seems my implementation only works half of the time. Although if I try implementing similar code within python, that code works 100% of the time. Could someone point me in the right direction?
--decompose n-1 as (2^s)*d
local function decompose(negOne)
exponent, remainder = 0, negOne
while (remainder%2) == 0 do
exponent = exponent+1
remainder = remainder/2
end
assert((2^exponent)*remainder == negOne and ((remainder%2) == 1), "Error setting up s and d value")
return exponent, remainder
end
local function isNotWitness(n, possibleWitness, exponent, remainder)
witness = (possibleWitness^remainder)%n
if (witness == 1) or (witness == n-1) then
return false
end
for _=0, exponent do
witness = (witness^2)%n
if witness == (n-1) then
return false
end
end
return true
end
--using miller-rabin primality testing
--n the integer to be tested, k the accuracy of the test
local function isProbablyPrime(n, accuracy)
if n <= 3 then
return n == 2 or n == 3
end
if (n%2) == 0 then
return false
end
exponent, remainder = decompose(n-1)
--checks if it is composite
for i=0, accuracy do
math.randomseed(os.time())
witness = math.random(2, n - 2)
if isNotWitness(n, witness, exponent, remainder) then
return false
end
end
--probably prime
return true
end
if isProbablyPrime(31, 30) then
print("prime")
else
print("nope")
end
Python has arbitrary length integers. Lua doesn't.
The problem is in witness = (possibleWitness^remainder)%n.
Lua is unable to calculate exact result of 29^15 % 31 directly.
There is a workaround working for numbers n < sqrt(2^53):
witness = mulmod(possibleWitness, remainder, n)
where
local function mulmod(a, e, m)
local result = 1
while e > 0 do
if e % 2 == 1 then
result = result * a % m
e = e - 1
end
e = e / 2
a = a * a % m
end
return result
end
I need Help adding a if clause to my Change Maker, so that if say I have denominations of coins that can't equal the input coin value. For Example I have Coins worth 2,4,6 and I have a Value of 1. I Want it to return Change Not Possible I tried adding a clause to it below but when I test it I get 1.#INF
I also am curious how I can find the optimal coin solution, So on top of saying the minimum number of coins it returns the optimal coin setup if there is one.
function ChangeMaking(D,n)
--[[
//Applies dynamic programming to find the minimum number of coins
//of denominations d1< d2 < . . . < dm where d1 = 1 that add up to a
//given amount n
//Input: Positive integer n and array D[1..m] of increasing positive
// integers indicating the coin denominations where D[1]= 1
//Output: The minimum number of coins that add up to n
]]
F = {} -- F is List Array of Coins
m = tablelength(D)
F[0] = 0
for i =1,n do
temp = math.huge
j = 1
while j <= m and i >= D[j] do
temp = math.min(F[ i - D[j] ], temp)
j = j + 1
end
F[i] = temp + 1
end
--I wanted to Catch the failed Solution here but I return 1.#INF instead
--if F[n] <= 0 and F[n] == 1.#INF then print("No Change Possible") return end
return F[n]
end
function main()
--[[
//Prints a Greeting, Asks for Denominations separated by spaces.
// Iterates through the input and assigns values to table
// Table is then input into ChangeMaker, and a while loop takes an n value for user input.
// User Enters 0 to end the Loop
]]
io.write("Hello Welcome the to Change Maker - LUA Edition\nEnter a series of change denominations, separated by spaces: ")
input = io.read()
deno = {}
for num in input:gmatch("%d+") do table.insert(deno,tonumber(num)) end
local i = 1
while i ~= 0 do
io.write("Please Enter Total for Change Maker, When Finished Enter 0 to Exit: ")
input2 = io.read("*n")
if input2 ~= 0 then io.write("\nMinimum # of Coins: " .. ChangeMaking(deno,input2).."\n") end
if input2 == 0 then i=0 print("0 Entered, Exiting Change Maker") end
end
end
function tablelength(T)
--[[
//Function for grabbing the total length of a table.
]]
local count = 0
for _ in pairs(T) do count = count + 1 end
return count
end
main()
I want to make a lua script that takes the input of a table, then outputs the strings in that table in their full width counterparts, eg
input = {"Hello", " ", "World"}
print(full(table.concat(input)))
and it will print "Ｈｅｌｌｏ Ｗｏｒｌｄ"
I tried it using this:
local encoding = [[ ０１２３４５６７８９ａｂｃｄｅｆｇｈｉｊｋｌｍｎｏｐｑｒｓｔｕｖｗｘｙｚＡＢＣＤＥＦＧＨＩＪＫＬＭＮＯＰＱＲＳＴＵＶＷＸＹＺ！゛＃＄％＆（）＊＋、ー。／：；〈＝〉？＠［\\］＾＿‘｛｜｝～]]
function char(i)
return encoding:sub(i:len(),i:len())
end
function decode(t)
for i=1,#t do t[i]=char(t[i]) end
return table.concat(t)
end
function returns(word, word_eol)
print(char(word_eol[2]))
end
but that did not work
note: it is a plugin for hexchat that's why I have it as print(char(word_eol[2])))
Because when you hook a command in hexchat it spits out a table that is the command name, then what was entered after
If (string) = [[ ０１２３４５６７８９ａｂｃｄｅｆｇｈｉｊｋｌｍｎｏｐｑｒｓｔｕｖｗｘｙｚＡＢＣＤＥＦＧＨＩＪＫＬＭＮＯＰＱＲＳＴＵＶＷＸＹＺ！゛＃＄％＆（）＊＋、ー。／：；〈＝〉？＠［\］＾＿‘｛｜｝～]], you're finding the n th character of (string), with n being the length of the character, which will always be one. If I understand correctly, this will do the job, by having a separate alphabet and matching the characters.
local encoding = [[ ０１２３４５６７８９ａｂｃｄｅｆｇｈｉｊｋｌｍｎｏｐｑｒｓｔｕｖｗｘｙｚＡＢＣＤＥＦＧＨＩＪＫＬＭＮＯＰＱＲＳＴＵＶＷＸＹＺ！゛＃＄％＆（）＊＋、ー。／：；〈＝〉？＠［］＾＿‘｛｜｝～]]
local decoding = [[ 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&()*+,-./:;{=}?#[]^_'{|}~]]
function char(i)
local l = decoding:find(i,1,true)
return encoding:sub(l,l)
end
function decode(t)
for i=1,#t do t[i]=char(t[i]) end
return table.concat(t)
end
function returns(word, word_eol)
print(char(word_eol[2]))
end
function full(s)
return (s:gsub('.', function(c)
c = c:byte()
if c == 0x20 then
return string.char(0xE3, 0x80, 0x80)
elseif c >= 0x21 and c <= 0x5F then
return string.char(0xEF, 0xBC, c+0x60)
elseif c >= 0x60 and c <= 0x7E then
return string.char(0xEF, 0xBD, c+0x20)
end
end))
end