【217】◀▶ IDL 控制语句说明

IDL> FOR i = 1, 10, 4 DO PRINT, i
1
5
9

FOR i = 1, 10, 4 DO BEGIN
PRINT, i
ENDFOR

IDL> strs = ["alex", "bn", "lee"]
IDL> FOREACH e, strs, i DO PRINT, i, "--", e
0--alex
1--bn
2--lee

strs = ["alex", "bn", "lee"]
FOREACH e, strs, i DO BEGIN
PRINT, i, "--", e
ENDFOREACH

IDL> i = 3
IDL> WHILE(i gt 0) DO PRINT, i--
3
2
1

i = 3
WHILE(i gt 0) DO BEGIN
PRINT, i--
ENDWHILE

IDL> A = 2
IDL> B = 3
IDL> IF(A EQ 2) AND (B EQ 3) THEN PRINT, 'A = ', A, STRING(13B), 'B = ', B
A =        2
B =        3

IDL> A = 2
IDL> IF(A EQ 2) THEN PRINT, 'A = ', A ELSE PRINT, 'A ≠ ', A
A =        2

A = 2
B = 3
IF(A EQ 2) AND (B EQ 3) THEN BEGIN
PRINT, 'A = ', A
PRINT, 'B = ', B
ENDIF

A = 2
IF(A EQ 2) THEN BEGIN
PRINT, 'A = ', A
ENDIF ELSE BEGIN
PRINT, 'A ≠ ', A
ENDELSE

x=1
CASE x OF
1: PRINT, 'one'
2: PRINT, 'two'
ENDCASE

IDL Prints:
one

x=2
CASE x OF
1: PRINT, 'one'
2: PRINT, 'two'
ELSE: PRINT, 'You entered: ', x
ENDCASE

IDL Prints:
two

x=3
CASE x OF
1: PRINT, 'one'
2: PRINT, 'two'
ELSE: BEGIN
PRINT, 'You entered: ', x
PRINT, 'Please enter a value between 1 and 2'
END
ENDCASE

IDL Prints:
You entered: 3
Please enter a value between 1 and 2

x=1
SWITCH x OF
1: PRINT, 'one'
2: PRINT, 'two'
ENDSWITCH

IDL Prints:
one
two

x=2
SWITCH x OF
1: PRINT, 'one'
2: PRINT, 'two'
ELSE: PRINT, 'You entered: ', x
ENDSWITCH

IDL Prints:
two
You entered:        2

x=2
SWITCH x OF
1: PRINT, 'one'
2: PRINT, 'two'
ELSE: BEGIN
PRINT, 'You entered: ', x
PRINT, 'Please enter a value between 1 and 2'
END
ENDSWITCH

IDL Prints:
two
You entered:        2
Please enter a value between 1 and 2

IDL> i = 3
IDL> REPEAT PRINT, i-- UNTIL(i lt 0)
3
2
1
0

i = 3
REPEAT BEGIN
PRINT, i--
ENDREP UNTIL(i lt 0)

CASE name OF
'Moe': BEGIN
PRINT, 'Stooge'
END
ENDCASE

SWITCH name OF
'Moe': BEGIN
PRINT, 'Stooge'
END
ENDSWITCH

FOR I = 1,10 DO BEGIN
; If odd, start next iteration:
IF (I AND 1) THEN CONTINUE
PRINT, I
ENDFOR

IDL Prints:
2
4
6
8
10

i = 0
PRINT, 'Initial value: ', i
WHILE (1) DO BEGIN
i = i + 1
IF (i eq 5) THEN BREAK
PRINT, 'Loop value: ', i
ENDWHILE
PRINT, 'END VALUE: ', i

IDL Prints:
Initial value:        0
Loop value:        1
Loop value:        2
Loop value:        3
Loop value:        4
END VALUE:        5