So i'm trying to convert python to lua but a road block i have right now is the class i'm not sure how i would convert a class to lua does anyone know how i would go about converting a class from python to lua?
python class
class
The OOP magic can be done with Lua tables and metatables.
Python
Look at The __init__() Function example here...
https://www.w3schools.com/python/python_classes.asp
Lets implement this with Lua...
( Lua 5.4 interactive console )
> _VERSION
Lua 5.4
> Person = setmetatable({},{
__call = function(self, name, age)
self.name = name
self.age = age
return {name = self.name, age = self.age}
end
})
> p1 = Person("John", 36)
> print(p1.name, p1.age)
John 36
So, some readers would ask: Why a metatabled table?
A simple function could do the same job.
Once a table has a metatable it is quit simple to add methods...
> Person = setmetatable({},{
__call = function(self, name, age)
self.name, self.age = name, age
table.insert(self, {name = self.name, age = self.age}) -- Numbered keys are the Data part
return {name = self.name, age = self.age}
end,
__index = {list = function(self) for i = 1, #self do print(self[i].name, self[i].age) end end}
})
> Person("John", 31);
> Person("Jack", 32);
> Person("Jim", 33);
> Person:list()
John 31
Jack 32
Jim 33
...that can handle the data of the table by itself.
Its a great benefit that the behaviour of a table can be controlled with metatables/methods.
And above example is only the tip of the iceberg.
Have a look at the __index of a string...
> for key, value in pairs(getmetatable(_VERSION).__index) do print(key, "=", value) end
byte = function: 0x565d6f20
lower = function: 0x565d4d90
len = function: 0x565d4750
sub = function: 0x565d7210
dump = function: 0x565d5d00
gsub = function: 0x565d7dc0
char = function: 0x565d5060
unpack = function: 0x565d6530
match = function: 0x565d7da0
packsize = function: 0x565d6420
pack = function: 0x565d6950
upper = function: 0x565d4ac0
format = function: 0x565d52d0
reverse = function: 0x565d4b50
find = function: 0x565d7db0
gmatch = function: 0x565d70d0
rep = function: 0x565d4be0
Therefore this is possible...
> print(("koyaanisqatsi"):upper():reverse())
ISTAQSINAAYOK
Means: Methods can be chained if their returning datatype has a method
Exceptions are: len() accept but dont return a string and sub() needs numbers before it returns a string also dump() needs a self defined function and returns a binary (almost unreadable) string.
Related
How can I add a method to the string table and modify self inside it ?
Basically, I'm trying to mimic the behaviour of the io.StringIO.read method in python, which reads n char in the string and returns them, modifying the string by "consuming" it.
I tried this:
function string.read(str, n)
to_return = str:sub(1, n)
str = str:sub(n + 1)
return to_return
end
local foo = "heyfoobarhello"
print(string.read(foo, 3))
print(foo)
Output is:
hey
heyfoobarhello
I expected the second line to be only foobarhello.
How can I achieve this ?
To mimic Python's io.StringIO class, you must make an object that stores both the underlying string and the current position within that string. Reading from an IO stream normally does not modify the underlying data.
local StringIO_mt = {
read = function(self, n)
n = n or #self.buffer - self.position + 1
local result = self.buffer:sub(self.position, self.position + n - 1)
self.position = self.position + n
return result
end,
}
StringIO_mt.__index = StringIO_mt
local function StringIO(buffer)
local o = {buffer = buffer, position = 1}
setmetatable(o, StringIO_mt)
return o
end
local foo = StringIO"heyfoobarhello"
print(foo:read(3))
print(foo:read())
Output:
hey
foobarhello
I don't recommend adding this class or method to Lua's string library, because the object has to be more complex than just a string.
You can add methods to the datatype string independently from the string table.
Short example that shows that the string methods even work if string table gets deleted...
string=nil
return _VERSION:upper():sub(1,3)
-- Returning: LUA
So you can add a method...
-- read.lua
local read = function(self, n1, n2)
return self:sub(n1, n2)
end
getmetatable(_VERSION).__index.read=read
return read
...for all strings.
( Not only _VERSION )
And use it...
do require('read') print(_VERSION:read(1,3):upper()) end
-- Print out: LUA
I want convert string to Map in grails. I already have a function of string to map conversion. Heres the code,
static def StringToMap(String reportValues){
Map result=[:]
result=reportValues.replace('[','').replace(']','').replace(' ','').split(',').inject([:]){map,token ->
List tokenizeStr=token.split(':');
tokenizeStr.size()>1?tokenizeStr?.with {map[it[0]?.toString()?.trim()]=it[1]?.toString()?.trim()}:tokenizeStr?.with {map[it[0]?.toString()?.trim()]=''}
map
}
return result
}
But, I have String with comma in the values, so the above function doesn't work for me. Heres my String
[program_type:, subsidiary_code:, groupName:, termination_date:, effective_date:, subsidiary_name:ABC, INC]
my function returns ABC only. not ABC, INC. I googled about it but couldnt find any concrete help.
Generally speaking, if I have to convert a Stringified Map to a Map object I try to make use of Eval.me. Your example String though isn't quite right to do so, if you had the following it would "just work":
// Note I have added '' around the values.
String a = "[program_type:'', subsidiary_code:'', groupName:'', termination_date:'', effective_date:'', subsidiary_name:'ABC']"
Map b = Eval.me(a)
// returns b = [program_type:, subsidiary_code:, groupName:, termination_date:, effective_date:, subsidiary_name:ABC]
If you have control of the String then if you can create it following this kind of pattern, it would be the easiest solution I suspect.
In case it is not possible to change the input parameter, this might be a not so clean and not so short option. It relies on the colon instead of comma values.
String reportValues = "[program_type:, subsidiary_code:, groupName:, termination_date:, effective_date:, subsidiary_name:ABC, INC]"
reportValues = reportValues[1..-2]
def m = reportValues.split(":")
def map = [:]
def length = m.size()
m.eachWithIndex { v, i ->
if(i != 0) {
List l = m[i].split(",")
if (i == length-1) {
map.put(m[i-1].split(",")[-1], l.join(","))
} else {
map.put(m[i-1].split(",")[-1], l[0..-2].join(","))
}
}
}
map.each {key, value -> println "key: " + key + " value: " + value}
BTW: Only use eval on trusted input, AFAIK it executes everything.
You could try messing around with this bit of code:
String tempString = "[program_type:11, 'aa':'bb', subsidiary_code:, groupName:, termination_date:, effective_date:, subsidiary_name:ABC, INC]"
List StringasList = tempString.tokenize('[],')
def finalMap=[:]
StringasList?.each { e->
def f = e?.split(':')
finalMap."${f[0]}"= f.size()>1 ? f[1] : null
}
println """-- tempString: ${tempString.getClass()} StringasList: ${StringasList.getClass()}
finalMap: ${finalMap.getClass()} \n Results\n finalMap ${finalMap}
"""
Above produces:
-- tempString: class java.lang.String StringasList: class java.util.ArrayList
finalMap: class java.util.LinkedHashMap
Results
finalMap [program_type:11, 'aa':'bb', subsidiary_code:null, groupName:null, termination_date:null, effective_date:null, subsidiary_name:ABC, INC:null]
It tokenizes the String then converts ArrayList by iterating through the list and passing each one again split against : into a map. It also has to check to ensure the size is greater than 1 otherwise it will break on f[1]
Here is the code i am trying to get working
def expr = ''
List params = []
params << 'filter-name'
params << 'servlet-name'
params << 'url-pattern'
params.each{expr = expr+ "it.'${it}'.text().trim()#"}
expr = expr.substring(0, expr.length()-1)
consNodes.each{
println "data is:$"{expr}"
println "actual : ${it.'filter-name'.text().trim()}#${it.'servlet-name'.text().trim()}#${it.'url-pattern'.text().trim()}"
}
in the above result comes like
data is:it.'filter-name'.text().trim()#it.'servlet-name'.text().trim()#it.'url-pattern'.text().trim()
actual : presenceLogoutFilter##/adfAuthentication/*
data is:it.'filter-name'.text().trim()#it.'servlet-name'.text().trim()#it.'url-pattern'.text().trim()
actual : remoteApplication##/rr/*
data is:it.'filter-name'.text().trim()#it.'servlet-name'.text().trim()#it.'url-pattern'.text().trim()
actual : ServletADFContextFilter#GetHandler#
data is:it.'filter-name'.text().trim()#it.'servlet-name'.text().trim()#it.'url-pattern'.text().trim()
actual : ServletADFContextFilter##/PresenceServlet/*
So, as you can see that my constructed expression is not able to evaluate further. Any advise on how to make it work?
The problem is that you're creating a GString like this: "it.'${it}'.text().trim()#", but then you're converting it into a String when you concatenate it: expr + "it.'${it}'.text().trim()#". Once you turn a GString into a String it no longer evaluates expressions. But even if you address that it won't solve your problem because GStrings do not evaluate like you think they do. The best way to explain it is with an example:
import org.codehaus.groovy.runtime.GStringImpl
// What you're doing
def a = 'John'
def b = 'Hello, $a'
def c = "${a}"
assert b == 'Hello, $a'
// What the compiler is doing (ignoring the variable name changes)
def aa = 'John'
def bb = 'Hello, $a'
def cc = new GStringImpl([] as Object[], ['Hello, $a'] as String[])
assert cc == 'Hello, $a'
// What you want the compiler to do, but it will not.
def aaa = 'John'
def bbb = 'Hello, $a'
def ccc = new GStringImpl(['John'] as Object[], ['Hello, '] as String[])
assert ccc == 'Hello, John'
If you really want to, you can build the GStrings manually, but that will be very difficult. And you'd end up depending on a class which is not guaranteed to remain backward-compatible between Groovy releases.
Here's what you can do instead:
def params = []
params << 'filter-name'
params << 'servlet-name'
params << 'url-pattern'
def evaluators = params.collect {
{ attr, node -> node[attr]?.text()?.trim() ?: '' }.curry(it)
}
consNodes.each { node ->
println evaluators.collect { c -> c(node) }.join('#')
}
The output looks like this:
presenceLogoutFilter##/adfAuthentication/*
remoteApplication##/rr/*
ServletADFContextFilter#GetHandler#
ServletADFContextFilter##/PresenceServlet/*
Instead of a single large expression you and up with a list of closures, each responsible for evaluating a node attribute. Then, you can join the results with '#'s.
How do I find the indexes of all the occurances of a substring in a large string -
(so basically ,and extension of the "indexOf" function) . Any ideas?
Current situation:
def text = " --- --- bcd -- bcd ---"
def sub = "bcd"
text.indexOf(sub)
// = 9
I want something like:
def text = " --- --- bcd -- bcd ---"
def sub = "bcd"
text.indexesOf(sub)
// = [9,15]
Is there such a function? How should I implement it otherwise? (in a non trivial way)
You could write a new addition to the String metaClass like so:
String.metaClass.indexesOf = { match ->
def ret = []
def idx = -1
while( ( idx = delegate.indexOf( match, idx + 1 ) ) > -1 ) {
ret << idx
}
ret
}
def text = " --- --- bcd -- bcd ---"
def sub = "bcd"
text.indexesOf(sub)
There is nothing I know of that exists in groovy currently that gets you this for free though
This is a relatively easy approach:
String.metaClass.indexesOf = { arg ->
def result = []
int index = delegate.indexOf(arg)
while (index != -1) {
result.add(index);
index = delegate.indexOf(arg, index+1);
}
return result;
}
Note that this will find overlapping instances (i.e. "fooo".indexesOf("oo") will return [1, 2]). If you don't want this, replace index+1 with index+arg.length().
What I have so far is:
def imageColumns = ["products_image", "procuts_subimage1", "products_subimage2", "prodcuts_subimage3", "products_subimage4"]
def imageValues = ["1.jpg","2.jpg","3.jpg"]
def imageColumnsValues = []
// only care for columns with values
imageValues.eachWithIndex { image,i ->
imageColumnsValues << "${imageColumns[i]} = '${image}'"
}
println imageColumnValuePair.join(", ")
It works but I think it could be better. Wish there was a collectWithIndex ... Any suggestions?
There's no collectWithIndex, but you can achieve the same result with a little effort:
def imageColumns = ["products_image", "procuts_subimage1", "products_subimage2", "prodcuts_subimage3", "products_subimage4"]
def imageValues = ["1.jpg","2.jpg","3.jpg"]
def imageColumnsValues = [imageValues, 0..<imageValues.size()].transpose().collect { image, i ->
"${imageColumns[i]} = '${image}'"
}
println imageColumnsValues.join(", ")
This takes the list of items and a range of numbers from 0 size(list) - 1, and zips them together with transpose. Then you can just collect over that result.