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Jigar Gosar
Jigar Gosar

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Elm: Guarantees Over Guidelines—Eliminate Bugs, Not Just Reduce Them

#elm #webdev

Elm vs. Functional Conventions: Guarantees That Eliminate Entire Classes of Errors

Elm's strict guarantees provide structural safety that functional conventions in multi-paradigm languages simply can't enforce. Let's look at some concrete examples of how Elm eliminates errors that would require discipline in other languages:

Example 1: Eliminating Null References (No Runtime Exceptions)

In JavaScript or TypeScript, developers rely on conventions like avoiding null or checking for undefined:

function getName(user?: { name: string }) {
  return user ? user.name : "Unknown"; // Manual check required
}
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Miss the check, and you’ll face runtime errors!

In Elm, this isn’t even a possibility—its type system requires all values to be handled explicitly:

getName : Maybe String -> String
getName maybeName =
    case maybeName of
        Just name -> name
        Nothing -> "Unknown" -- No accidental `null`
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The compiler forces exhaustive handling, eliminating null-related crashes entirely.

Example 2: Enforcing Pure Functions

In JavaScript, functional purity relies on developer discipline:

let count = 0; 

function increment() {
  count += 1; // Mutates external state, leading to unexpected bugs
}
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Without strict enforcement, side effects sneak into code.

In Elm, functions are pure by design. You simply cannot modify outside state:

increment count = count + 1 -- Always returns a new value, no hidden state mutation
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By enforcing purity at the language level, Elm prevents unintended state changes altogether.

Example 3: Exhaustive Case Analysis Prevents Edge Case Errors

In TypeScript, developers must manually ensure every possible case is handled:

type Status = "Success" | "Error" | "Loading";

function handleStatus(status: Status) {
  if (status === "Success") {
    return "Operation complete";
  } else if (status === "Error") {
    return "Something went wrong";
  }
  // Missing "Loading" case—leads to undefined behavior
}
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Elm requires handling all cases explicitly, preventing these oversights:

type Status = Success | Error | Loading

handleStatus : Status -> String
handleStatus status =
    case status of
        Success -> "Operation complete"
        Error -> "Something went wrong"
        Loading -> "Please wait..."
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No forgotten cases—no silent failures!

Conclusion: Why Elm Wins Over Developer Discipline

Functional conventions in multi-paradigm languages can reduce errors, but they rely on developers following best practices—an inherently fragile approach.

Elm ensures correctness by design, eliminating entire classes of errors rather than simply reducing their likelihood. With guarantees like enforced purity, exhaustive case handling, and immutability, developers spend less time debugging and more time building robust, maintainable applications.

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