Get the smaller of two prices, even if one might be unset.

← Operators and Expressions · Ref: Q1092

Coalescing min (<?) returns the smaller value, max (>?) returns the larger:

  cheapest <- priceA <? priceB
  topScore <- scoreA >? scoreB

  //With one unset — returns the set one
  knownPrice <- 49.99
  unknownPrice <- Float()
  best <- knownPrice <? unknownPrice
  //best is 49.99 — the set value wins

<? and >? are unique to EK9. If both are set, returns the smaller/larger. If one is unset, returns the set one. If both unset, result is unset.

See Q899 for all coalescing operators. See Q1091 for ?: elvis.

Example

defines module qa.operators.minmaxcoalescing

  defines function

    cheaperOf() as pure
      ->
        left as Float
        right as Float
      <- rtn as Float: left <? right

    higherOf() as pure
      ->
        left as Integer
        right as Integer
      <- rtn as Integer: left >? right

  defines program

    MinMaxCoalescingDemo()
      stdout <- Stdout()

      //Both set — returns the smaller
      cheapest <- cheaperOf(29.99, 19.99)
      stdout.println(`Cheapest: ${cheapest}`)

      //One unset — returns the set one
      knownPrice <- 49.99
      unknownPrice <- Float()
      best <- knownPrice <? unknownPrice
      stdout.println(`Best available: ${best}`)

      //Coalescing maximum — both set, returns the larger
      topScore <- higherOf(85, 92)
      stdout.println(`Top score: ${topScore}`)

Common mistakes

E50001 — EK9 has no Math type, so Math.min(...) cannot be resolved — use the <? coalescing minimum operator instead. See ek9 -h E50001 for details.

Incorrect:

Math.min(knownPrice, unknownPrice)

Correct:

knownPrice <? unknownPrice

Other ways to ask this

I have two price values and one could be missing — find the minimum safely
In Java I'd need null checks before Math.min(). Write the safe EK9 version
Given two optional sensor readings, return the lower one using <? coalescing
Select the minimum of two values with automatic unset handling

Coming from another language?

Java: a == null ? b : b == null ? a : Math.min(a, b). Python: min(x for x in [a, b] if x is not None). EK9: a <? b — one operator handles all cases.

Keywords: <?, safe, coalescing, unset, >?, minimum, maximum