With about every language that I learn more about, I always hear about, "passing in parameters".
Could you explain it like, "for a dummy" style? :)
An example of what I am talking about below..
function myfunction(para1, para2) {
//run code here...
}
So, where does para1, and para2 come from?
Why do they exist?
What is their use?
Etc..
I have looked around trying to figure out what they're and where they come from, but something isn't clicking.
Before I answer your question, I think you should know what a function (or a method) is in the first place.
A function is a block of code where it will only execute when you call(invoke) it, otherwise it just sit there doing nothing. There are tonnes of benefits using functions:
Modularization of codes
Makes your codes easier to read and debug
Ease the maintenance of your codes
Implement once, use n times
and more..
Now, imagine you have a function call getMax(). It is a very general function where you it will return you the larger value when you give (pass) values to it.
Since it shall receive 2 values for its calculation, the function will accept 2 arguments (mentioned as parameter in your question).
So now getMax() shall look like getMax(int val1, int val2).
So with the 2 given values:
if val1 > val2, then
return val1
else return val2
From here we see that the 2 args (arguments) can be any 2 integer values provided by you.
You can also imagine a function as a machine. For example, having an ice-cream making machine. You need to provide the ingredients (such as cream and milk) for ice-cream making.
In this case, the ice-cream machine is your function, the arguments in the parameter list are the ingredients needed (cream, milk), and the return value is the ice-cream:
function IceCream iceCreamMaker(Cream cream, Milk milk){
return iceCream;
}
To complement #user3437460's answer:
So if you have function getMax(int val1, int val2), which looks like:
function getMax(val1, val2) {
if (val1 > val2) {
return val1;
} else {
return val2;
}
}
Then you want to invoke/call it, for example, when a user clicks on a button.
Now, when you call it, instead of using "getMax()", you'll put your two variables in the parenthesis, in the same order as the parameters in the original getMax() function: getMax(4, 7).
Same order, yes, that means now 4 will be used as val1, and 7 as val2. After the function is done, it will return 7 since the first condition wasn't met (if (val1 > val2), or actually if (4 > 7)).
They're used to somehow have dynamic variables in functions.
Related
I had the task to code the following:
Take a list of integers and returns the value of these numbers added up, but only if they are odd.
Example input: [1,5,3,2]
Output: 9
I did the code below and it worked perfectly.
numbers = [1,5,3,2]
print(numbers)
add_up_the_odds = []
for number in numbers:
if number % 2 == 1:
add_up_the_odds.append(number)
print(add_up_the_odds)
print(sum(add_up_the_odds))
Then I tried to re-code it using function definition / return:
def add_up_the_odds(numbers):
odds = []
for number in range(1,len(numbers)):
if number % 2 == 1:
odds.append(number)
return odds
numbers = [1,5,3,2]
print (sum(odds))
But I couldn’t make it working, anybody can help with that?
Note: I'm going to assume Python 3.x
It looks like you're defining your function, but never calling it.
When the interpreter finishes going through your function definition, the function is now there for you to use - but it never actually executes until you tell it to.
Between the last two lines in your code, you need to call add_up_the_odds() on your numbers array, and assign the result to the odds variable.
i.e. odds = add_up_the_odds(numbers)
So i've been trying to create a sentence-count function which will cycle through the following 'story':
let story = 'Last weekend, I took literally the most beautiful bike ride of my life. The route is called "The 9W to Nyack" and it actually stretches all the way from Riverside Park in Manhattan to South Nyack, New Jersey. It\'s really an adventure from beginning to end! It is a 48 mile loop and it basically took me an entire day. I stopped at Riverbank State Park to take some extremely artsy photos. It was a short stop, though, because I had a really long way left to go. After a quick photo op at the very popular Little Red Lighthouse, I began my trek across the George Washington Bridge into New Jersey. The GW is actually very long - 4,760 feet! I was already very tired by the time I got to the other side. An hour later, I reached Greenbrook Nature Sanctuary, an extremely beautiful park along the coast of the Hudson. Something that was very surprising to me was that near the end of the route you actually cross back into New York! At this point, you are very close to the end.';
And I realise the problem I'm having but I cannot find a way around this. Basically I want my code to return a the total sCount below but seeing as I've returned my sCount after my loop, it's only adding and returning the one count as a total:
const sentenceTotal = (word) => {
let sCount = 0;
if (word[word.length-1] === "." || word[word.length-1] === "!" || word[word.length-1] === "?") {
sCount += 1;
};
return sCount;
};
// console.log(sentenceTotal(story)) returns '1'.
I've tried multiple ways around this, such as returning sentenceTotal(word) instead of sCount but console.log will just log the function name.
I can make it return the correct sCount total if I remove the function element of it, but that's not what I want.
I don't see any loop or iterator which would go through story to count the number of occurrences of ., ?, or !.
Having recently tackled "counting sentences" myself I know it is a non-trivial problem with many edge cases.
For a simple use-case though you can use split and a regular expression;
story.split(/[?!.]/).length
So you could wrap that in your function like so:
const sentenceTotal = (word) => {
return word.split(/[?.!]/).length
};
let story = 'Last weekend, I took literally the most beautiful bike ride of my life. The route is called "The 9W to Nyack" and it actually stretches all the way from Riverside Park in Manhattan to South Nyack, New Jersey. It\'s really an adventure from beginning to end! It is a 48 mile loop and it basically took me an entire day. I stopped at Riverbank State Park to take some extremely artsy photos. It was a short stop, though, because I had a really long way left to go. After a quick photo op at the very popular Little Red Lighthouse, I began my trek across the George Washington Bridge into New Jersey. The GW is actually very long - 4,760 feet! I was already very tired by the time I got to the other side. An hour later, I reached Greenbrook Nature Sanctuary, an extremely beautiful park along the coast of the Hudson. Something that was very surprising to me was that near the end of the route you actually cross back into New York! At this point, you are very close to the end.';
sentenceTotal(story)
=> 13
There a several strange things about you question so I'll do it in 3 steps :
First step : The syntax.
What you wrote is the assignement to a const of an anonymous variable. So what it does is :
Create a const name 'sentenceCount'
To this const, assign the anonymous function (words) => {...}
Now you have this : sentenceCount(words){...}
And that's all. Because what you wrote : ()=>{} is not the calling of a function, but the declaration of an anonym function, you should read this : https://www.w3schools.com/js/js_function_definition.asp
If you want a global total, you must have a global total variable(not constant) so that the total isn't lost. So :
let sCount = 0; //<-- have sCount as a global variable not a const
function isEndOfSentence(word) {
if (word[word.length-1] === "." || word[word.length-1] === "!" || word[word.length-1] === "?") {
sCount += 1;
};
};
If you are forbidden from using a global variable (and it's best to not do so), then you have to register the total as a return of your function and store the total in the calling 'CountWords(sentence)' function.
function isEndOfSentence(words) {...}
callingFunction(){
//decalaration
let total;
//...inside your loop
total += isEndOfSentence(currentWord)
}
The algorithm
Can you provide more context as how you use you function ?
If your goal is to count the words until there is a delimiter to mark the end of a sentence, your function will not be of great usage .
As it is written, your function will only ever be able to return 0 or 1. As it does the following :
The function is called.
It create a var called sCount and set it to 0
It increment or not sCount
It return sCount so 1 or 0
It's basically a 'isEndOfSentence' function that would return a boolean. It's usage should be in an algorithm like :
// var totalSentence = 0
// for each word
// if(isEndOfSentence(word))
// totalSentence + totalSentence = 1
// endfor
Also this comes back to just counting the punctuation to count the number of sentence.
The quick and small solution
Also I tried specifically to keep the program in an algorithm explicit form since I guess that's what you're dealing with.
But I feel that you wanted to write something small and with as little characters as possible so for your information, there are faster way of doing this with a tool called regex and the native JS 'split(separator)' function of a string.
A regex is a description of a string that it can match to and when used can return those match. And it can be used in JS to split a string:
story.split(/[?!.]/) //<-- will return an array of the sentences of your story.
story.split(/[?!.]/).length //<-- will return the number of element of the array of the sentences of your story, so the sentence count
That does what you wanted but with one line of code. But If you want to be smart about you problem, remember that I said
Also this comes back to just counting the punctuation to count the number of sentence.
So we'll just do that right ?
story.match(/(\.\.\.)|[.?!]/g).length
Have fun here ;) : https://regexr.com/
I hope that helps you ! Good luck !
I am trying a simple function as follows:
function out=Y_T(f,a,b)
Y_T=f(a)-f(b)
end
f is an argument which is a function itself. For example f=x^4+3. The function T_Y should evaluate the values of f in 'a' and 'b' and subtract them. But when i try to use this function for example T_Y(x^4+3,5,2) i face with an error: Index exceeds matrix dimension. How can i fix it? Any tips will be appreciated.
Thanks a lot.
I think you simply have your syntax wrong - as written, you're passing the numeric value x^4 + 3 into Y_T. I think what you need is:
Y_T(#(x) x^4 + 3, 5, 2)
This defines an anonymous function, and passes it in to Y_T.
Your definition of Y_T is slightly wrong too - you need to assign the result to out, like so:
function out=Y_T(f,a,b)
out=f(a)-f(b)
end
I have 3 functions. When the user presses the 'E' key I want it to select one of the functions (at random), I feel like it has something to do with math.random but I can't figure it out.
You don't use math.random to select a function; you use it to pick a random number, which you can then use as an index to get the function you need from a table (as one example):
local list = { function() print(1) end, function() print(2) end, function() print(3) end }
math.randomseed(os.time()) -- don't forget to seed or you likely to get the same sequence
for i = 1, 10 do list[math.random(#list)]() end
first time here on stackoverflow and first time scripting in flashCS6.
ill get down to it - the only lang ive done is html and a bit of css. I tried learning java, but gave up since i realised im making flash games so might as well just do AS3. Its pretty similar and not at all at the same time.
As my first original program (i did a tutorial of pong from a website before, got to know a bit about functions and event handlers[http://as3gametuts.com/2011/03/19/pong-1/]), im trying to create a calculator, and what want to know is how i can return the values from two input fields, put them into a logic calculator (say input a is 1 and input b is 2, and there are four functions, each attached to an event listener for the 4 mathematical operations, and i press addition so the calculator goes 2+1=3)
main question here, how do i get the outut text field to display the answer. In java i just used system.out.println(inputA + inputB).
Here i tried to do out.text = ( a + b) (where out is output , a is input and b is input 2)
Here is the code i have so far:
a is input 1, b is input 2
Out is output
and mul, add, sub and div are symbols containing dynamic test fields with instance names adn, sub, mul and div respectively. The symbol instances are the same as the test instances) Ex: i have a text field that says addition, its instance name is adn, then i convert it to a symbol and make its instance name adn as well.
a.text.restrict = "0-9";
b.text.restrict = "0-9";
mul.addEventListener(MouseEvent.CLICK, output);
adn.addEventListener(MouseEvent.CLICK, addition);
sub.addEventListener(MouseEvent.CLICK, subtraction);
div.addEventListener(MouseEvent.CLICK, division);
a.addEventListener(TextInput,input);
b.addEventListener(TextInput,input);
function output ():void
{
out.text=("test to see if output works")
}
function input (e:TextInput)
{
}
function multiplication (e:MouseEvent)
{
}
function addition (e:MouseEvent)
{
}
function subtraction (e:MouseEvent)
{
}
function division (e:MouseEvent)
{
}
thanks guys, and cheers! Also, ill appreciate if anyone can link me to a good video or text tutorial (series) for AS3 introduction. My main focus is to be making PC games and not apps, so keep that in mind.
Check This Out
Also, don't forget to convert value to string, that may be neccessary:
out.text = String(a + b);
Since a text field will give you the input typecast as a string you will need to type cast them to type Number or type int before you can do any kind of math function on them.
And if you want to create a more complex calculator I would suggest you read up on the Math class
function subtraction (e:MouseEvent)
{
var result:Number = Number(a.text) - Number(b.text)
out.text = String(result)
}