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Control Flow Keywords

Control flow keywords direct program execution based on conditions and patterns.

Overview

Keyword Used With Purpose
IF THEN, ELSE Conditional expression
THEN IF, WHEN Consequent result
ELSE IF Alternative result
CONSIDER WHEN Pattern matching
WHEN CONSIDER Pattern case
OTHERWISE CONSIDER Default case
BRANCH IF Multi-way conditional

IF / THEN / ELSE

Conditional expressions that choose between two alternatives.

Syntax

IF condition THEN trueResult ELSE falseResult

Examples

DECIDE status IS
  IF age >= 18 THEN "adult" ELSE "minor"

See IF for complete documentation.

CONSIDER / WHEN / OTHERWISE

Pattern matching for examining values and executing different branches.

Syntax

CONSIDER value
  WHEN pattern1 THEN result1
  WHEN pattern2 THEN result2
  OTHERWISE defaultResult

Examples

DECLARE Color IS ONE OF Red, Green, Blue

GIVEN c IS A Color
colorName c MEANS
  CONSIDER c
    WHEN Red THEN "red"
    WHEN Green THEN "green"
    WHEN Blue THEN "blue"

See CONSIDER for complete documentation.

BRANCH

Multi-way conditional for flat comparison chains. Alternative to nested IF statements.

Syntax

BRANCH IF condition1 THEN result1
       IF condition2 THEN result2
       IF condition3 THEN result3
       OTHERWISE default

Examples

DECLARE Category IS ONE OF Standard, Premium, Enterprise

GIVEN cat IS A Category
GIVETH A NUMBER
priceFor cat MEANS
  BRANCH IF cat EQUALS Standard   THEN 10
         IF cat EQUALS Premium    THEN 25
         IF cat EQUALS Enterprise THEN 100
         OTHERWISE 0

BRANCH vs CONSIDER vs IF

Use Case Best Choice
Binary decision IF...THEN...ELSE
Multiple equality checks BRANCH
Pattern matching / destructuring CONSIDER
Nested conditions Nested IF or CONSIDER

THEN

Marks the result expression in conditionals.

  • With IF: IF condition THEN result ELSE alternative
  • With WHEN: WHEN pattern THEN result
  • With BRANCH: BRANCH IF condition THEN result

ELSE

Marks the alternative result when condition is false.

IF x > 0 THEN "positive" ELSE "not positive"

Note: ELSE is required in IF expressions — there's no "dangling else" ambiguity.

OTHERWISE

Default case in CONSIDER/BRANCH when no pattern matches.

CONSIDER status
  WHEN Active THEN "running"
  WHEN Paused THEN "waiting"
  OTHERWISE "unknown"

Best Practice: Always include OTHERWISE unless you've covered all cases.

  • IF - Detailed conditional documentation
  • CONSIDER - Detailed pattern matching documentation
  • AND / OR - Combine conditions

See Also