E11050: operator returns a value but result is discarded - assign to variable or use in expression

What went wrong

An operator that returns a value was used as a standalone statement. The computed result is discarded — this is dead code.

Operators like +, -, *, /, ==, <>, contains, matches, length, ?, $ return values that represent the computation result. Discarding them means the computation was pointless.

Worked examples

Compilable examples demonstrating this error and the correct fix:

• ek9 -q 815 (Why is calling a computational operator without using its...)

Rationale

EK9's operator model is precise: mutating operators (+=, -=, :=:, ++, --) return Void because the side-effect IS the purpose. Computational operators return values because the VALUE is the purpose. If you discard that value, the statement achieves nothing.

How to fix it

1. Assign the result: total <- price + tax
2. Use in an expression: if price > limit
3. If the side-effect was intended, use the mutating operator instead: price += tax

See also

• E11051: discarded pure method return
• E11052: discarded Result or Optional

Examples

Every example is compiled by the EK9 compiler: the first fails exactly as captioned, the others fix it.

Fails with E11050: operator returns a value but result is discarded - assign to variable or use in expression

#!ek9
defines module error.e11050.bad

  defines function

    testDiscardedComparisonOperator()
      a <- "hello"
      b <- "world"
      a.==(b)

    testDiscardedAddOperator()
      a <- 10
      b <- 20
      a.+(b)

    testDiscardedNotEqualOperator()
      a <- "hello"
      b <- "world"
      a.<>(b)

Fixed: Use the result of the operator

#!ek9
defines module error.e11050.good

  defines function

    sameWord()
      <- rtn as Boolean?
      first <- "hello"
      second <- "world"
      rtn: first == second

    total()
      <- rtn as Integer?
      first <- 10
      second <- 20
      rtn: first + second

Questions and answers

These Q&A entries show E11050 and its fix:

• Q815: Why is calling a computational operator without using its result an error in EK9?