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Control Structures

Control words are used in Explicit Definition (:) and are punctuation that determine the sequence of execution. Matching control words and the enclosed sentences make up a control structure. The following control words and structures are available:
assert. T



for.     T do. B end.
for_xyz. T do. B end.


if. T do. B end.

if. T do. B else. B1 end.

if.     T  do. B
elseif. T1 do. B1
elseif. T2 do. B2


select. T
 case.  T0 do. B0
 fcase. T1 do. B1
 case.  T2 do. B2


try. B catch. B1 catchd. B2 catcht. B3 end.

while.  T do. B end.
whilst. T do. B end.
Words beginning with B or T denote blocks, comprising zero or more simple sentences and control structures. The last sentence executed in a T block is tested for a non-zero value in its leading atom, and determines the block to be executed next. (An empty T block result or an omitted T block tests true.) The final result is the result of the last sentence executed that was not in a T block, and if there is no such last executed sentence, the final result is i.0 0 .

These control words and control structures are further detailed in the immediately following pages.

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