Review this function. Is it too complex?

← Getting Started · Ref: Q1030

Yes, a single function that validates input, calculates a result and formats output would be too complex. Each concern should be a separate pure function.

The code shown is the decomposed result:
- validateAmount: checks the value is usable
- calculateWithTax: does the arithmetic
- formatCurrency: converts to a display string

Benefits:
- Each function is testable in isolation
- Pure functions can be reused elsewhere
- The main function becomes a pipeline of clear steps
- Complexity is distributed across small, readable units

EK9 encourages small pure functions composed together. When a function has multiple responsibilities, split it.

Example

defines module qa.gettingstarted.reviewcomplexity

  defines function

    validateAmount() as pure
      -> amount as Float
      <- rtn as Boolean: amount?

    calculateWithTax() as pure
      ->
        amount as Float
        taxRate as Float
      <- rtn as Float: amount + (amount * taxRate)

    formatCurrency() as pure
      -> amount as Float
      <- rtn as String: `Total: ${amount}`

  defines program

    ComplexityDemo()
      stdout <- Stdout()

      amount <- 99.50
      taxRate <- 0.20

      if validateAmount(amount)
        total <- calculateWithTax(amount, taxRate)
        stdout.println(formatCurrency(total))
      else
        stdout.println("Invalid amount")

      //An unset amount is rejected by the same check
      missingAmount <- Float()
      if validateAmount(missingAmount)
        stdout.println(formatCurrency(calculateWithTax(missingAmount, taxRate)))
      else
        stdout.println("Invalid amount")

Common mistakes

E11031 — 'value' is a banned non-descriptive variable name in EK9 — use a meaningful identifier such as 'total'. See ek9 -h E11031 for details.

Incorrect:

        value <- calculateWithTax(amount, taxRate)
        stdout.println(formatCurrency(value))

Correct:

        total <- calculateWithTax(amount, taxRate)
        stdout.println(formatCurrency(total))

Other ways to ask this

Is this code doing too much in one function?
Should I break this function into smaller pieces?
Assess the complexity of this EK9 function

Coming from another language?

EK9 encourages small, pure functions composed together. Split complex functions into single-responsibility pieces.

Keywords: review, function, pure, split, complexity