if (condition trueCallable falseCallable -- branchResult)

Builtins

Name introduction, declaration modifiers, and module binding: NAME: ...;, codeRef, def, exportFunction, importFunction, importVariable, overload, private, static, use, and virtual.
Struct construction forms: (...), {...}, and array.
Selection forms: source-text selection with NAME and .NAME, read-only source-text selection with @NAME and .@NAME, and ordinal or known-name data-input selection with @, callField, and fieldRead.
Writing forms: source-text selection with !NAME and .!NAME, ordinal selection with ! and fieldWrite, and already-selected destination replacement with set.
Calling and control flow: call, if, loop, ucall, and uif.
Text operations: &, LF, attribute, textSize, and textSplit.
Condition constants, value comparison, and logical operators: <, =, >, DEBUG, FALSE, TRUE, and, is, lshift, or, rshift, xor, and ~.
Arithmetic and numeric transforms: *, +, -, /, ^, cast, ceil, cos, floor, log, log10, mod, neg, sin, and sqrt.
Reference, creation, and value-state operations: const, dynamic, isConst, isDirty, isDynamic, isRef, isStatic, known?, new, newVarOfTheSameType, stable?, unconst, and unknownStable?.
Schema and struct introspection: code?, codeRef?, fieldCount, fieldIndex, fieldIsRef, fieldIsVirtual, fieldName, has, isCombined, managed?, same, schemaName, and virtual?.
Storage and manual lifetime operations: addressToReference, alignment, manuallyDestroyVariable, manuallyInitVariable, storageAddress, and storageSize.
Diagnostics and compile-time failure: failCompilation, getCallTrace, printCompilerMessage, printStack, printStackTrace, and raiseStaticError.

if (condition trueCallable falseCallable -- branchResult)

Inputs

condition: Non-NIL Cond that selects or merges branches.

trueCallable: Already-selected Block called when condition is true.

falseCallable: Already-selected Block called when condition is false.

Outputs

branchResult: Result produced by the selected branch, or merged branch result when the condition is unknown at compile time.

if selects between two already-selected Block branches by one non-NIL Cond value.

The selected branch is called through a normal call boundary. Locals created inside a branch do not remain available afterward.

For a known condition, only the selected branch is called. The unselected branch is ignored and may be invalid. For an unknown condition, both branches are compiled separately and their outputs are merged.

Behavior

condition must be a non-NIL Cond value.

Both branch inputs must be Block values already on the data stack.

Any additional data inputs used by a branch must already be below condition, trueCallable, and falseCallable on the data stack.

Before a branch is called or compiled, condition, trueCallable, and falseCallable are removed from the stack. Each branch sees only the remaining underlying data stack as its input.

For a known condition, TRUE selects the first branch and FALSE selects the second branch.

For an unknown condition, both branches are compiled from the same input stack.

When both branches are compiled, their stack outputs must be compatible; otherwise compilation fails.

The final output stack depends on the selected branch or on the merged result of both branches.

Example

{} 0 {} [ "-- known TRUE selects the first branch --" printCompilerMessage TRUE [ 1 ] [ impossibleName ] if printStack _:; "-- known FALSE selects the second branch --" printCompilerMessage FALSE [ impossibleOtherName ] [ 2 ] if printStack _:; condition: FALSE dynamic; "-- unknown condition compiles both branches --" printCompilerMessage condition [ "-- unknown true branch --" printCompilerMessage 1 ] [ "-- unknown false branch --" printCompilerMessage 2 ] if printStack _:; 0 ] "main" exportFunction

Expected Output During Compilation

-- known TRUE selects the first branch -- 1 -- known FALSE selects the second branch -- 2 -- unknown condition compiles both branches -- -- unknown true branch -- -- unknown false branch -- Int32