Comment by Tarmil on Why is it so slow to create records with a field that...
The thing is, for Set, you need not just equality but comparison. And you can't really do comparison by reference in .NET. So I think you have 2 choices. 1: Add a Guid to BigType, fill it with...
View ArticleComment by Tarmil on Catching inner exception in F# async block
You can't use reraise in an async though. But come to think of it, you can also just skip this branch and it will be reraised by async.
View ArticleComment by Tarmil on How to use FSharp.Data.JsonProvider dynamically?
@JoshDredge Edited the answer for this case.
View ArticleComment by Tarmil on Implementing let! ... and! ... in a custom Computation...
Unfortunately the link to the RFC is dead in the announcement blog; here is the correct address: github.com/fsharp/fslang-design/blob/main/FSharp-5.0/…
View ArticleComment by Tarmil on F# How to use an anonymous type in place of a full typed...
I think you're looking for an equivalent of C#'s new(15000f) aka target-typed new expressions? There isn't one in F#.
View ArticleComment by Tarmil on Value option for optional parameters in F#?
@sdgfsdh Yes, this parameter will also be treated as optional by an F# caller.
View ArticleComment by Tarmil on F# script can't find nuget package - probably because...
You can specify a source in the script with #i "nuget: https://...". But I don't think it completely overrides the ones in your global config, it just adds one.
View ArticleComment by Tarmil on How to Parse a DateTime in a specific timezone in .Net 6...
@MrDatKookerellaLtd In GetUtcOffset, the unspecified date is interpreted as a datetime in the Sydney timezone.
View ArticleComment by Tarmil on F#: How can I wrap a non-async value in Async
"in your use case it won't work, due to eager evaluation of the argument." On the contrary, it would be a closer equivalent of Task.FromResult, which is also eager.
View ArticleComment by Tarmil on Why does module rec result in a warning?
@sdgfsdh Yes, it can be determined statically. I guess the point of not doing it is to discourage the use of module rec as a way to just reorder declarations that are not actually mutually recursive.
View ArticleComment by Tarmil on Type method appears to call private functions in an...
In fact, seq<T> isn't just implemented via IEnumerable<T>; it's a simple alias for IEnumerable<T>.
View ArticleComment by Tarmil on Unexpected result with F# type check
Yeah, the fact that null doesn't match :? obj is expected, but the compiler definitely shouldn't warn that it always does!
View ArticleComment by Tarmil on How to make anchors work when switching between two...
It's in Bolero, you need to open Bolero.Remoting.Client. (and I should move it to Bolero, it would be better there)
View ArticleAnswer by Tarmil for F# query expression: How to do a left join and return on...
I think this should do the trick:query { for student in db.Student do leftOuterJoin selection in db.CourseSelection on (student.StudentID = selection.StudentID) into result where (not (result.Any()))...
View ArticleAnswer by Tarmil for F# query expression nested lists
What you're doing is pretty much exactly what groupJoin does.let events = query { for event in db.Events do groupJoin ea in db.EventAttendances on (event.Id = ea.EventId) into result select (event,...
View ArticleAnswer by Tarmil for Can't get bind operator to work with discriminated union
When you use an operator, F# looks for it in order:as a let-defined operator;as a static member-defined operator on one of the two arguments' types. Here, the arguments you are passing to the operator...
View ArticleAnswer by Tarmil for Generating custom data in FsCheck
To always generate valid Quality and ShelfLife, you need to register Arbitrary instances:type Arbs = static member Quality() = Arb.Default.NonNegativeInt() |> Arb.convert (fun (NonNegativeInt x)...
View ArticleAnswer by Tarmil for F# unit of measure to model area
There are several things here:You need to define area as being a square length with type area = radius * radius. Otherwise the compiler has no way to match your input and output units.Pi, when used...
View ArticleAnswer by Tarmil for F# Discriminated Union - "downcasting" to subtype
This is a common mistake when coming from an OO language: there are no subtypes involved in this code. The fact that you named your union cases the same as the type of the field they contain can make...
View ArticleAnswer by Tarmil for How to specify the result type for F# function's signature?
You can put a type annotation for the return value at the end of the declaration line:static member TryParse(s: string): SocialAccount option =As an aside, static member X = fun ... -> is not...
View ArticleAnswer by Tarmil for FParsec and postfix modifiers to parsed items
I think you can use opt to allow parseCount to not find a count if there isn't one:let parseCount = parseTerm .>>. opt (choice [ skipChar '*'>>% (MinCount 0) skipChar '+'>>% (MinCount...
View ArticleAnswer by Tarmil for What are the differences between in .fsx, .fsi and .fs...
.fsx is for individual files intended to run as a script. In particular, in an .fsx file you can use things like #r "Foo.dll" to dynamically load a library and #load "Foo.fsx" to load another script...
View ArticleAnswer by Tarmil for External JS library not applied to tag generated by...
The problem is that you have jQuery included twice: once by you manually in your index.html, and once by WebSharper automatically for its own purposes. So all the functionality added by TypeAhead and...
View ArticleAnswer by Tarmil for F# Async let! & return! computation expression
No, there are no default implementations for computation expression methods. If you want want special behavior for Async<'T option>, you can add an extension method to AsyncBuilder. It looks like...
View ArticleAnswer by Tarmil for F# create instance method for a constrained generic...
As mentioned by @brianberns in the comments, not directly. However, C#-style extension methods can be defined for a specialized version of a class. The caveat is that as an extension method, it won't...
View ArticleAnswer by Tarmil for Pattern match multiple dates
when can be added to a whole pattern, not to nested patterns, so you need something like this:match (startDate, endDate) with| d, e when d = DateTime.MinValue && e = DateTime.MinValue -> 0|...
View ArticleAnswer by Tarmil for Reflection doesn't work only with webassembly
As @JL0PD correctly guessed in their comment, this is because Bolero's tryfsharp runs an older compiler that doesn't support nameof.Updating it has been on my to-do list for ever, but there have been...
View ArticleAnswer by Tarmil for How do you override `GetHashCode()` idiomatically for an...
The recommended way to combine hash codes since .NET Standard 2.1 is using System.HashCode.Combine(). To differentiate between cases, you can add an integer argument.override this.GetHashCode() = match...
View ArticleAnswer by Tarmil for How to get Elmah working with .Net 6 F# Web Api Project
The equivalent in F#, and with asp.net minimal API that you are using, would be to put this before let app = ...:builder.Services.AddElmah<SqlErrorLog>(fun options -> options.ConnectionString...
View ArticleAnswer by Tarmil for Why Does F# Pattern Matching for a String Type Match a...
When you use an identifier in a pattern, you're not testing equality with an existing value (or type). Instead, you're defining a pattern that always matches, and giving the matched value the given...
View ArticleAnswer by Tarmil for How can I install the Fantomas Tool with the latest...
In version 5, the name of the package has changed from fantomas-tool to just fantomas. So you should uninstall fantomas-tool and install fantomas instead.
View ArticleAnswer by Tarmil for Why got "expected class or object definition" in very...
On Unix, fsc is the Scala compiler, not F#.Given how old Expert F# 4.0 is, I assume it suggested installing mono; in this case, the F# compiler is fsharpc.If you have the dotnet SDK instead, then the...
View ArticleAnswer by Tarmil for Apparent non-coherent behaviour between F# and C# when...
This is indeed a limitation in F#, you can't have a subtype constraint on two type parameters, ie 'T :> 'U. I think there's a language design suggestion to remove this limitation, although I can't...
View ArticleAnswer by Tarmil for Error when using MathNet.Numerics Fit.Line with F# tuple...
You should be able to use the struct keyword in the pattern part of let to deconstruct a struct tuple:let struct(Tau, Mu) = Fit.Line(shearRate, shearStress)
View ArticleAnswer by Tarmil for Moving FParsec code to an F# module does not work
As explained by @Gus in the comments, the problem is that parsers have a second type parameter for user data, that was disambiguated by the call to run in the original code but not in the modularized...
View ArticleAnswer by Tarmil for NullReferenceException in F# interactive
As @Jim Foye pointed out, the best way to go is to reference the package with #r "nuget:".As for why your original code throws an exception: the assemblies in the ref folder of a package, when there is...
View ArticleAnswer by Tarmil for What is a "sealed" type in F# and why doesn't the type...
Sealed types are a .NET concept. They are types that cannot be inherited from. This includes:F# recordsF# unionsF# classes declared with the [<Sealed>] attributeC# classes declared with the...
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