To: J3                                                     J3/26-224
From: Malcolm Cohen
Subject: Interp F23/030 on conditional arguments/expressions
Date: 2026-October-26


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NUMBER: F23/030
TITLE: Are conditional expressions allowed as actual arguments?
KEYWORDS: conditional expression, conditional argument
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress
REFERENCES: 24-007

QUESTION:

Consider

    ! a and b are variables.
    CALL sub( ( a>b ? a : b ) )

Is the actual argument
(i) a conditional-arg, in which case the effective argument is one of
    the variables a or b, and the dummy argument is definable, or
(ii) an expr that is a conditional-expr, in which case the effective
     argument is the value of a or b, and the dummy argument is not
     definable.

Constraint C1535 says
   "An actual-arg that is an expr shall not be a variable or a
    conditional-arg."

However, that does not rule out the conditional-expr case.
In fact it is impossible to reach the conditional-arg production
starting from expr, other than in a nested function reference,
thus an expr cannot be a conditional-arg, i.e. the constraint
does not do anything.

This program fragment thus seems to be ambiguous, and thus not
conforming.

Should this program fragment be conforming, and if so, how is the
ambiguity resolved?

ANSWER:

This was intended to be conforming, and the actual argument should be
a conditional-arg.

An edit is provided to correct the mistake in constraint C1535.
After this edit, an actual-arg cannot be a conditional-expr; however,
no functionality is lost, as it can still be a parenthesised
conditional-expr.

EDIT to 24-007.

[322:4] 15.5.1 Syntax of a procedure reference,
        C1535 beginning "An actual-arg that is an expr..."
        change "conditional-arg" to "conditional-expr".

SUBMITTED BY: Malcolm Cohen

HISTORY: 26-nnn   m241  Submitted

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