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What is F# best for?

F# is a universal programming language for writing succinct, robust and performant code. F# allows you to write uncluttered, self-documenting code, where your focus remains on your problem domain, rather than the details of programming.

learn.microsoft.com - What is F# | Microsoft Learn
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Table of contents

What is F#

Article

10/13/2022

2 minutes to read

11 contributors Feedback

In this article

F# is a universal programming language for writing succinct, robust and performant code. F# allows you to write uncluttered, self-documenting code, where your focus remains on your problem domain, rather than the details of programming. It does this without compromising on speed and compatibility - it is open-source, cross-platform and interoperable. open System // Gets access to functionality in System namespace. // Defines a list of names let names = [ "Peter"; "Julia"; "Xi" ] // Defines a function that takes a name and produces a greeting. let getGreeting name = $"Hello, {name}" // Prints a greeting for each name! names |> List.map getGreeting |> List.iter (fun greeting -> printfn $"{greeting}! Enjoy your F#")

F# has numerous features, including:

Lightweight syntax

Immutable by default

Type inference and automatic generalization

First-class functions

Powerful data types

Pattern matching

Async programming

A full set of features are documented in the F# language guide.

Rich data types

Types such as Records and Discriminated Unions let you represent your data.

// Group data with Records type SuccessfulWithdrawal = { Amount: decimal Balance: decimal } type FailedWithdrawal = { Amount: decimal Balance: decimal IsOverdraft: bool } // Use discriminated unions to represent data of 1 or more forms type WithdrawalResult = | Success of SuccessfulWithdrawal | InsufficientFunds of FailedWithdrawal | CardExpired of System.DateTime | UndisclosedFailure F# records and discriminated unions are non-null, immutable, and comparable by default, making them very easy to use.

Correctness with functions and pattern matching

F# functions are easy to define. When combined with pattern matching, they allow you to define behavior whose correctness is enforced by the compiler. // Returns a WithdrawalResult let withdrawMoney amount = // Implementation elided let handleWithdrawal amount = let w = withdrawMoney amount // The F# compiler enforces accounting for each case! match w with | Success s -> printfn $"Successfully withdrew %f{s.Amount}" | InsufficientFunds f -> printfn $"Failed: balance is %f{f.Balance}" | CardExpired d -> printfn $"Failed: card expired on {d}" | UndisclosedFailure -> printfn "Failed: unknown :(" F# functions are also first-class, meaning they can be passed as parameters and returned from other functions.

Functions to define operations on objects

F# has full support for objects, which are useful when you need to blend data and functionality. F# members and functions can be defined to manipulate objects. type Set<'T when 'T: comparison>(elements: seq<'T>) = member s.IsEmpty = // Implementation elided member s.Contains (value) =// Implementation elided member s.Add (value) = // Implementation elided // ... // Further Implementation elided // ... interface IEnumerable<'T> interface IReadOnlyCollection<'T> module Set = let isEmpty (set: Set<'T>) = set.IsEmpty let contains element (set: Set<'T>) = set.Contains(element) let add value (set: Set<'T>) = set.Add(value) In F#, you will often write code that treats objects as a type for functions to manipulate. Features such as generic interfaces, object expressions, and judicious use of members are common in larger F# programs. To learn more about a larger set of F# features, check out the F# Tour.

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What heart rate is too high by age?

To estimate your maximum age-related heart rate, subtract your age from 220. For example, for a 50-year-old person, the estimated maximum age-related heart rate would be calculated as 220 – 50 years = 170 beats per minute (bpm).

cdc.gov - Target Heart Rate and Estimated Maximum Heart Rate - CDC

One way of checking physical activity intensity is to determine whether your pulse or heart rate is within the target zone during physical activity. 1 For moderate-intensity physical activity, your target heart rate should be between 64% and 76%1,2 of your maximum heart rate. You can estimate your maximum heart rate based on your age. To estimate your maximum age-related heart rate, subtract your age from 220. For example, for a 50-year-old person, the estimated maximum age-related heart rate would be calculated as 220 – 50 years = 170 beats per minute (bpm). The 64% and 76% levels would be:

64% level: 170 x 0.64 = 109 bpm, and

76% level: 170 x 0.76 = 129 bpm

This shows that moderate-intensity physical activity for a 50-year-old person will require that the heart rate remains between 109 and 129 bpm during physical activity. For vigorous-intensity physical activity, your target heart rate should be between 77% and 93%1,2 of your maximum heart rate. To figure out this range, follow the same formula used above, except change “64 and 76%” to “77 and 93%”. For example, for a 35-year-old person, the estimated maximum age-related heart rate would be calculated as 220 – 35 years = 185 beats per minute (bpm). The 77% and 93% levels would be:

77% level: 185 x 0.77 = 142 bpm, and

93% level: 185 x 0.93 = 172 bpm

This shows that vigorous-intensity physical activity for a 35-year-old person will require that the heart rate remains between 142 and 172 bpm during physical activity.

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