CONTROL STATEMENTS
This chapter reviews the GDL commands available for controlling loops and subroutines in scripts and introduces the concept of buffer manipulation designed to store parameter values for further use. It also explains how to use objects as macro calls and how to display calculated expressions on screen.
FLOW CONTROL STATEMENTS
FOR
FOR variable_name = initial_value TO end_value [ STEP step_value ]
First statement of a FOR loop. If the STEP keyword and the step_value are missing, the step is assumed to be 1. A global variable is not allowed as a loop control variable.
Example:
FOR I=1 TO 10 STEP 2 PRINT I
NEXT I
NEXT
NEXT variable_name
Last statement of a FOR loop.
The loop variable varies from the initial_value to the end_value by the step_value increment (or decrement) in each execution of the body of the loop (statements between the FOR and NEXT statements). If the loop variable exceeds the value of the end_value, the program executes the statement following the NEXT statement.
Note: Changing the step_value during the execution of the loop has no effect.
ArchiCAD 11 GDL Reference Guide |
209 |
Control Statements
The two program fragments below are equivalent:
!1st A = B
1:IF C > 0 AND A > D OR C < 0 AND A < D THEN 2 PRINT A
A = A + C GOTO 1
2:
!2nd
FOR A = B TO D STEP C PRINT A
NEXT A
The above example shows that step_value = 0 causes an infinite loop.
Only one NEXT statement is allowed after a FOR statement. You can exit the loop with a GOTO (or IF ... GOTO) statement and to return after leaving, but you cannot enter a loop skipping the FOR statement.
DO
DO
[statment1
statement2
...
statementn]
WHILE condition
The statements between the keywords are executed as long as the condition is true. The condition is checked after each execution of the statements.
WHILE condition DO [statement1 statement2
...
statementn]
ENDWHILE
The statements between the keywords are executed as long as the condition is true. The condition is checked before each execution of the statements.
210 |
ArchiCAD 11 GDL Reference Guide |
Control Statements
REPEAT
[statement1
statement2
...
statementn]
UNTIL condition
The statements between the keywords are executed until the condition becomes true. The condition is checked after each execution of the statements.
Example:
The following four sequences of GDL commands are equivalent:
! 1st
FOR i = 1 TO 5 STEP 1 BRICK 0.5, 0.5, 0.1 ADDZ 0.3
NEXT i ! 2nd i = 1 DO
BRICK 0.5, 0.5, 0.1 ADDZ 0.3
i = i + 1 WHILE i <= 5 ! 3rd
i = 1
WHILE i <= 5 DO
BRICK 0.5, 0.5, 0.1 ADDZ 0.3
i = i + 1 ENDWHILE
! 4th i = 1 REPEAT
BRICK 0.5, 0.5, 0.1 ADDZ 0.3
i = i + 1 UNTIL i > 5
ArchiCAD 11 GDL Reference Guide |
211 |
Control Statements
IF
IF condition THEN label IF condition GOTO label IF condition GOSUB label
Conditional jump statement. If the value of the condition expression is 0, the command has no effect, otherwise execution continues at the label.
Examples:
IF A THEN 28
IF I > J GOTO 200+I*J IF I > 0 GOSUB 9000
IF condition THEN statement [ELSE statement] or
IF condition THEN [statement1 statement2
...
statementn]
[ELSE
statementn+1
statementn2
...
statementn+m] ENDIF
If you write only one command after keywords THEN and/or ELSE in the same row, there is no need for ENDIF. A command after THEN or ELSE in the same row means a definite ENDIF.
If there is a new row after THEN, the successive commands (all of them until the keyword ELSE or ENDIF) will only be executed if the expression in the condition is true (other than zero). Otherwise, the commands following ELSE will be carried out. If the ELSE keyword is absent, the commands after ENDIF will be carried out.
212 |
ArchiCAD 11 GDL Reference Guide |