C#•3mo 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 🇸🇪OP•3mo 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•3mo ago

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

Merineth 🇸🇪OP•3mo 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•3mo ago

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

Merineth 🇸🇪OP•3mo ago

Hmmm

int topofstack = mainstack[mainstack.top];

int topofstack = mainstack[mainstack.top];

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

Angius•3mo ago

What attributes?

Merineth 🇸🇪OP•3mo ago

Merineth 🇸🇪OP•3mo 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•3mo ago

it's private

Merineth 🇸🇪OP•3mo ago

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

Angius•3mo ago

C# defaults to lowest access if no access is specified

Merineth 🇸🇪OP•3mo ago

I see

Merineth 🇸🇪OP•3mo ago

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

Angius•3mo ago

Does Stack have an indexer?

Merineth 🇸🇪OP•3mo ago

indexer?

Angius•3mo ago

This tells me that it does not:

Angius•3mo 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 🇸🇪OP•3mo ago

:harold:

Angius•3mo 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 🇸🇪OP•3mo ago

Got another related question i think

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

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

Merineth 🇸🇪OP•3mo 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•3mo 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 🇸🇪OP•3mo ago

mainstack.top is an integer

Angius•3mo ago

Yes

Merineth 🇸🇪OP•3mo ago

Can i convert int to double?

Angius•3mo ago

Sure But you cannot use a double to index an array

Merineth 🇸🇪OP•3mo ago

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

Angius•3mo ago

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

Merineth 🇸🇪OP•3mo ago

yea

Angius•3mo ago

Why would you convert anything here?

Merineth 🇸🇪OP•3mo ago

AAAh

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

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

` Is that what you meant?

Angius•3mo ago

That seems better, yes

Merineth 🇸🇪OP•3mo ago

nicee very smart of you

Angius•3mo ago

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

MODiX•3mo 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 🇸🇪OP•3mo ago

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

Merineth 🇸🇪OP•3mo ago

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

Angius•3mo ago

Does it exist in the same class?

Merineth 🇸🇪OP•3mo ago

Noo it's in a differenty class

Merineth 🇸🇪OP•3mo ago

Angius•3mo ago

Well there you go, then

Merineth 🇸🇪OP•3mo ago

But both the class and the method are public

Angius•3mo 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 🇸🇪OP•3mo ago

Aaaah right i completely forgot about that 🧠 It worked!

Angius•3mo ago

nice

Merineth 🇸🇪OP•3mo ago

Got another question :sadcat:

Angius•3mo ago

Shoot

Merineth 🇸🇪OP•3mo 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•3mo ago

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

Merineth 🇸🇪OP•3mo ago

In my folder on my pc?

Angius•3mo ago

In Visual Studio

Merineth 🇸🇪OP•3mo ago

Do you mean in the code?

Angius•3mo ago

Merineth 🇸🇪OP•3mo ago

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

Angius•3mo 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 🇸🇪OP•3mo ago

Angius•3mo 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 🇸🇪OP•3mo ago

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

Angius•3mo ago

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

Merineth 🇸🇪OP•3mo 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 🇸🇪OP•3mo ago

when applying a foreach loop

Angius•3mo ago

WriteAllLines It expects an array of lines

Merineth 🇸🇪OP•3mo 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•3mo 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 🇸🇪OP•3mo ago

Oh damn i didn't even think of that hehe

Merineth 🇸🇪OP•3mo ago

Shouldn't outputlines be defined inside my foreach loop?

Angius•3mo 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 🇸🇪OP•3mo ago

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

Angius•3mo ago

Nope

Merineth 🇸🇪OP•3mo ago

Nice works now!

Merineth 🇸🇪OP•3mo ago

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

Angius•3mo 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 🇸🇪OP•3mo ago

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

Angius•3mo ago

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

Merineth 🇸🇪OP•3mo ago

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

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

Angius•3mo ago

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

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

Merineth 🇸🇪OP•3mo ago

ohh

Angius•3mo ago

A parameter

Merineth 🇸🇪OP•3mo ago

I thought it was pass it as an argument

Angius•3mo ago

$structure

MODiX•3mo 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 🇸🇪OP•3mo ago

Or rather everything inside () are arguments

Angius•3mo ago

Here's the naming reference

Merineth 🇸🇪OP•3mo 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•3mo 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•3mo 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 🇸🇪OP•3mo ago

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

Merineth 🇸🇪OP•3mo ago

It should output the exception into the output file

Angius•3mo 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 🇸🇪OP•3mo ago

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

Merineth 🇸🇪OP•3mo 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?