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CONTROL STRUCTURES
These are abbreviated details from the section WORD
LIST grouped here for convenience. The numbers n can be negative or
positive 16-bit integers. There are similar control structures in assembler,
see the section STRUCTURED CONTROL
IN ASSEMBLER.
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n2 n1 DO .
LOOP
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Loop n2-n1 times, maximum
32767 times but will always loop at least once. Index starts with n1 and
increments at LOOP each time around
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n2 n1 DO .
n3 +LOOP
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Similar but index increases
by n3 each time giving a maximum number of loops of INT((n2-n1))/n3)
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BEGIN . f UNTIL
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Loops until f is true (non-zero)
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BEGIN . AGAIN
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Indefinite loop used only as top level of hierarchy of
software, such as the word entered at power-up or the word executed by
another task
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BEGIN . f WHILE . REPEAT
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Most general of loops. Circulates around
BEGIN and
REPEAT
until f is true, when execution jumps from
WHILE
to after REPEAT
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n IF . ELSE . THEN
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Executes code from IF to ELSE if
n is true, otherwise executes the code from ELSE to THEN
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RECURSE
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Execute the current word definition, occasionally preferable
to loops
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CASE w OF .
ENDOF
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Executes one of many possible
sections of
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x OF . ENDOF
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code. nx represents possible
value(s)
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y
OF . ENDOF
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of n. cond is any conditional
such as
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...
(more if needed) ...
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> = or < . See example in WORD
LIST
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R nx cond IFCASE . ENDOF
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...
(default if none of above) ...
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ENDCASE
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