@IF function

The REXX @IF function is used to test for specific values within a REXX expression and then interpret the associated REXX expressions and return the results.

The @IF function can be used anywhere a REXX expression may be entered. REXX expressions can be used in FORM.CALC, FORM.CONDITIONS and FORM.COLUMNS (Column Definition)

           .-+---+-----------------------------------.
           | '-,-'                                   |
           V              (1)                   (2)  |
>>-@IF--(----comparison_1-------,--expression_1------+---------->

                   (3)
>--,--expression_N-------)-------------------------------------><

1. A valid REXX expression that can be reduced to a 0 or 1. Typically contains a REXX comparative operator. The @IF function tests the comparison and if the result is 1, the following expression is evaluated and the results are returned. The @IF function evaluates the comparisons left to right until a true comparison is found. If no comparsions are found to be true, then the last expression is interpreted and the results are returned.
2. A valid REXX expression consisting of terms (strings, symbols, and functions) interspersed with operators and parenthesis. If the preceding comparison is true, the expression is interpreted and the results are returned.
3. A valid REXX expression as defined above. If no comparisons are true, then expression_N is interpreted and he results are returned.

Notes on the @IF function:

• There must be an odd number of arguments.
• The minimum number of arguments is 3, the maximum is 19.
• The first token must be @IF and it must be immediately followed by a left parenthesis.
• Arguments must be delimited by commas.
• The argument list must end with a right parenthesis.
• The last argument serves as an "otherwise" or default expression.
• If an odd numbered argument is not the last, then it is a comparison.
• If PASS NULLS is set to YES and the expression contains a substitution variable that is null, undefined, overflow, has no instance, or no relationship, then the entire expression will be set to the value that represents that condition. This reduction is performed only on expressions, not comparisons.
• If PASS NULLS is set to YES and the expression contains more than one substitution variable that is null, undefined, overflow, has no instance, or no relationship, then the following order of precedence will be used for expression reduction:
  1. Undefined
  2. Overflow
  3. Null
  4. No instance
  5. No relationship

  The use of multiple arguments (comparisons and expressions) passed to the @IF function will eliminate the need to nest @IF functions (nested @IF functions are not supported for expression reduction).