Remote-processing CAMBASIC Manuel d'utilisateur télécharger pdf (Page 72)

Commands - 39

DO/UNTIL

Statements

SYNTAX: DO

UNTIL expression is true

PURPOSE: To execute a conditional loop structure.

REMARK S: The DO/ UNT IL statements cause a list of statements to be executed until a condition is met. You

may exit a DO/UNTIL with the EXIT statement

EXAMPLE: 10 A= - 45

20 DO

30 INC A:PRINT A

50 UNTIL A=0

Nesting DO/UNT IL loops is permitted. Care must be taken in the construct. The following

example illustrates one of the possible pitfalls:

10 DO

20 DO

30 INC X

40 UNTIL X=5

50 INC Y

60 UNTIL Y=5

In the “inside” loop beginning at line 20, variable X is incremented until X = 5. Line 50 is then

executed. Since Y is now 1, execution branches to line 20. T he prev ious value of X was 5, and it is

now incremented to 6. Since this is greater than 5, the inside loop continues until X overflows (a

very long time).

One solution is to add line 45 to reset X each time so the program will run properly:

45 X=0

ERROR: < UNTIL> – if UNTIL encountered without corresponding DO.

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Remote-processing CAMBASIC Manuel d'utilisateur Page 72