C#•3w ago

✅ Is it possible to Parse a string and identify it's type?

I want to scan an index of an array and identify if it's an operator such as (+,-,*) or if it's an operand (doubles). Is this possible?

101 Replies

Merineth 🇸🇪•3w ago

            while (stack != null)
            {
                
                if (stack.top == )

            while (stack != null)
            {
                
                if (stack.top == )

basically in my if statement i'm triyng to identify if the string at the top of the stack is an operator or operand My guess would be an if else statement to check the operators? else it's an operand?

Angius•3w ago

You can use an if/else, you can use a switch, sure

Merineth 🇸🇪•3w ago

nice Also by any chance, do you know how i can identify the length of an array? Does C# have a CBL for such a method?

Angius•3w ago

uh .Length? Or .Count, I can never remember which is arrays which is lists

Merineth 🇸🇪•3w ago

Hmmm

int topofstack = mainstack[mainstack.top];

int topofstack = mainstack[mainstack.top];

Are attributes not a part of the object that we create?

Angius•3w ago

What attributes?

Merineth 🇸🇪•3w ago

Merineth 🇸🇪•3w ago

I'm trying to access the attribute "top" But it says it's not accessible because of it's protection level even tho the class is public

Angius•3w ago

it's private

Merineth 🇸🇪•3w ago

oh i have to set the attributes to public if i want to use them?

Angius•3w ago

C# defaults to lowest access if no access is specified

Merineth 🇸🇪•3w ago

I see

Merineth 🇸🇪•3w ago

I don't get the type error? top is of type int

Angius•3w ago

Does Stack have an indexer?

Merineth 🇸🇪•3w ago

indexer?

Angius•3w ago

This tells me that it does not:

Angius•3w ago

Yes You can't just get an element from anything with [9] or what have you That thing must have an indexer Yout StackArray field in Stack is an array, so that one would have an indexer by default You could do mainstack.StackArray[mainstack.top] But not mainstack[mainstack.top] Not unless you implement an indexer

Merineth 🇸🇪•3w ago

:harold:

Angius•3w ago

https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/indexers/using-indexers

Using Indexers - C#

Learn how to declare and use an indexer for a class, struct, or interface in C#. This article includes example code.

Merineth 🇸🇪•3w ago

Got another related question i think

right = mainstack.StackArray[Convert.ToDouble(mainstack.top)];

right = mainstack.StackArray[Convert.ToDouble(mainstack.top)];

Merineth 🇸🇪•3w ago

I'm trying to set right which is a double to the value at mainstack.StackArray[mainstack.top] Can i not convert a string to a double? "Cannot implicitly convert type string to double" I'm not entirely sure what that means

Angius•3w ago

You can parse a string into a double, yes But mainstack.top is not a string And you cannot index arrays with doubles

Merineth 🇸🇪•3w ago

mainstack.top is an integer

Angius•3w ago

Yes

Merineth 🇸🇪•3w ago

Can i convert int to double?

Angius•3w ago

Sure But you cannot use a double to index an array

Merineth 🇸🇪•3w ago

Ahhh So i have to convert it first and then assign it to right?

Angius•3w ago

uh You use ints to index arrays mainstack.top is an int

Merineth 🇸🇪•3w ago

yea

Angius•3w ago

Why would you convert anything here?

Merineth 🇸🇪•3w ago

AAAh

                        right = Convert.ToDouble(mainstack.StackArray[mainstack.top]);

                        right = Convert.ToDouble(mainstack.StackArray[mainstack.top]);

` Is that what you meant?

Angius•3w ago

That seems better, yes

Merineth 🇸🇪•3w ago

nicee very smart of you

Angius•3w ago

Also, it's generally better to use double.TryParse() since it handles the string not being a double better

MODiX•3w ago

Angius

REPL Result: Success

string[] str = { "1.4", "0", "chair", " ", "", "0.1" };
foreach (var s in str)
{
    var isDouble = double.TryParse(s, out var num);
    if (isDouble)
    {
        Console.WriteLine($"Double of value {num}");
    }
    else
    {
        Console.WriteLine($"'{s}' is not a double");
    }
}

string[] str = { "1.4", "0", "chair", " ", "", "0.1" };
foreach (var s in str)
{
    var isDouble = double.TryParse(s, out var num);
    if (isDouble)
    {
        Console.WriteLine($"Double of value {num}");
    }
    else
    {
        Console.WriteLine($"'{s}' is not a double");
    }
}

Console Output

Double of value 1.4
Double of value 0
'chair' is not a double
' ' is not a double
'' is not a double
Double of value 0.1

Double of value 1.4
Double of value 0
'chair' is not a double
' ' is not a double
'' is not a double
Double of value 0.1

Compile: 521.251ms | Execution: 59.278ms | React with ❌ to remove this embed.

Merineth 🇸🇪•3w ago

Ahh i see C# is so confusing sometimes I don't really understand why some errors occur

Merineth 🇸🇪•3w ago

Here for example. It says it doesn't exists, even tho it's clearly public ?

Angius•3w ago

Does it exist in the same class?

Merineth 🇸🇪•3w ago

Noo it's in a differenty class

Merineth 🇸🇪•3w ago

Angius•3w ago

Well there you go, then

Merineth 🇸🇪•3w ago

But both the class and the method are public

Angius•3w ago

Sure But this method is a member of a specific class You can't just reference it and not the class If the method is static, you just do Class.Method() If the method is not static, you need an instance of the class first

var c = new Class();
c.Method();

var c = new Class();
c.Method();

Merineth 🇸🇪•3w ago

Aaaah right i completely forgot about that 🧠 It worked!

Angius•3w ago

nice

Merineth 🇸🇪•3w ago

Got another question :sadcat:

Angius•3w ago

Shoot

Merineth 🇸🇪•3w ago

I'm trying to read/write of files. One input.txt and output.txt. They are located in C:\Users\aljom\Documents\Plugg Programmering filer\OOP\Assignment1\Assignment1\Calculator\Calculator\bin\Debug\net6.0. in my code i set my filepath to

            string inputfile = @"\input.txt";
            string outputfile = @"\output.txt";

            string inputfile = @"\input.txt";
            string outputfile = @"\output.txt";

It couldn't find them, not exactly sure what i messed up

Angius•3w ago

Right-click on each of those files, go to properties, set them to be copied always or copied if newer

Merineth 🇸🇪•3w ago

In my folder on my pc?

Angius•3w ago

In Visual Studio

Merineth 🇸🇪•3w ago

Do you mean in the code?

Angius•3w ago

Merineth 🇸🇪•3w ago

Or should they be in the same file location as my solution explorer?

Angius•3w ago

Ideally, place them next to the .csproj Then right-click them And do what I mentioned When doing so, they will be automatically copied to that .bin folder when the project gets built and ran

Merineth 🇸🇪•3w ago

Angius•3w ago

Remove that \ Or replace it with ./ \ refers to the root, the root of the drive in this case No slash or ./ will refer to the current working directory

Merineth 🇸🇪•3w ago

Ooh ok the code ran! i'm not sure tho where it got placed the copies that is

Angius•3w ago

Probably in that .bin/debug/......

Merineth 🇸🇪•3w ago

Yeah i found them! now all that remains is fix the code since it's not outputting wha ti want xD I got a quick question about foreach loop and StreamWriter

Merineth 🇸🇪•3w ago

when applying a foreach loop

Angius•3w ago

WriteAllLines It expects an array of lines

Merineth 🇸🇪•3w ago

ooh In that case, are there any substitution to it? Or would i have to take my double and convert it into an array of lines?

Angius•3w ago

There are many options You can keep appending to the file in the loop Could use a stringbuilder to build a single string and use WriteAllText() Could store the calculated results in another array/list and write those as lines And that can be done with either a loop like here, or LINQ Plenty of choices

Merineth 🇸🇪•3w ago

Oh damn i didn't even think of that hehe

Merineth 🇸🇪•3w ago

Shouldn't outputlines be defined inside my foreach loop?

Angius•3w ago

outputlines has no value It's empty, uninitialized You have a space that says "apple crates go here" You're trying to put an apple in a crate But there are no crates

Merineth 🇸🇪•3w ago

haha okay that makes sense I just assume it auto initialized like in C

Angius•3w ago

Nope

Merineth 🇸🇪•3w ago

Nice works now!

Merineth 🇸🇪•3w ago

Can the string 2.5 not be converted to decimals? (or even double, i tried making it double)

Angius•3w ago

I'm assuming you live in a country that uses a comma as decimal separator 😄 Just need to pass CultureInfo.InvariantCulture as the second parameter Or any other culture that uses a period Alternatively, you can set the culture of the whole thread

Merineth 🇸🇪•3w ago

Hmmm How do i pass CultureInfo.InvariantCulture as a second parameter?

Angius•3w ago

Just... do? Assuming Convert.ToDecimal() takes it

Merineth 🇸🇪•3w ago

                        right = Convert.ToDecimal.CultureInfo.InvariantCulture(mainstack.StackArray[mainstack.top]);

                        right = Convert.ToDecimal.CultureInfo.InvariantCulture(mainstack.StackArray[mainstack.top]);

Angius•3w ago

Convert.ToDecimal("123.45", CultureInfo.InvariantCulture)

Convert.ToDecimal("123.45", CultureInfo.InvariantCulture)

Merineth 🇸🇪•3w ago

ohh

Angius•3w ago

A parameter

Merineth 🇸🇪•3w ago

I thought it was pass it as an argument

Angius•3w ago

$structure

MODiX•3w ago

namespace Namespace;

[Attribute]
public class Class
{
    public string PublicField;
    private bool _privateField;    

    public int PublicProperty { get; set; }

    public Class() {} // Constructor

    public void Method(int parameter)
    {
        var localVariable = parameter; 

        int LocalMethod(string param) { return 3; }
    } 
}

namespace Namespace;

[Attribute]
public class Class
{
    public string PublicField;
    private bool _privateField;    

    public int PublicProperty { get; set; }

    public Class() {} // Constructor

    public void Method(int parameter)
    {
        var localVariable = parameter; 

        int LocalMethod(string param) { return 3; }
    } 
}

Merineth 🇸🇪•3w ago

Or rather everything inside () are arguments

Angius•3w ago

Here's the naming reference

Merineth 🇸🇪•3w ago

Aah i see! I'm a little unclear how to handle exceptions

                        try
                        {
                            right = Convert.ToDecimal(mainstack.StackArray[mainstack.top], CultureInfo.InvariantCulture);
                        }
                        catch (FormatException)
                        {
                            
                        }

                        try
                        {
                            right = Convert.ToDecimal(mainstack.StackArray[mainstack.top], CultureInfo.InvariantCulture);
                        }
                        catch (FormatException)
                        {
                            
                        }

Angius•3w ago

Remember when I mentioned the TryParse() method? Like that So you don't get exceptions but a nice bool you can check with a regular if $tryparse

MODiX•3w ago

When you don't know if a string is actually a number when handling user input, use int.TryParse (or variants, e.g. double.TryParse)

if(int.TryParse("123", out int number))
{
    var total = number + 1;
    Console.WriteLine(total); // output: 124
}

if(int.TryParse("123", out int number))
{
    var total = number + 1;
    Console.WriteLine(total); // output: 124
}

TryParse returns a bool, where true indicates successful parsing. Remarks: - Avoid int.Parse if you do not know if the value parsed is definitely a number. - Avoid Convert.ToInt32 entirely, this is an older method and Parse should be preferred where you know the string can be parsed. Read more here

Merineth 🇸🇪•3w ago

Well i think in our assignment we want to get an exception Basically when the user tries different things

Merineth 🇸🇪•3w ago

It should output the exception into the output file

Angius•3w ago

Ah Then yeah, you handle exceptions with a try/catch But the thing in the image here I think is about creating and throwing your own exceptions

Merineth 🇸🇪•3w ago

Yes, most likely Okay i watched a few videos and tried again

Merineth 🇸🇪•3w ago

However i have nooo idea how to return it? xD

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✅ Is it possible to Parse a string and identify it's type?