CODEWITHSUNDEEP
idl-programming-language
I gillespie
I gillespie

Reputation: 39

KEYWORD_SET in IDL

I am new to IDL and find the KEYWORD_SET difficult to grasp. I understand that it is a go no go switch. I think its the knocking on and off part that I am having difficulty with. I have written a small program to master this as such

Pro get_this_done, keyword1 = keyword1 

WW=[3,6,8]

PRINT,'WW'
print,WW

y= WW*3
IF KEYWORD_Set(keyword1) Then BEGIN  
   print,'y'
   print,y

ENDIF
Return
END

WW prints but print, y is restricted by the keyword. How do I knock off the keyword to allow y to print. Silly little question, but if somebody can indulge me, it would be great.

Upvotes: 0

Views: 519

Answers (2)

planetmaker
planetmaker

Reputation: 6044

Keywords are simply passed as arguments to the function:

get_this_done, KEYWORD1='whatever'

or also

get_this_done, /KEYWORD1

which will give KEYWORD1 the INT value of 1 inside the function. Inside the function KEYWORD_SET will return 1 (TRUE) when the keyword was passed any kind of value - no matter whether it makes sense or not.

Thus as a side note to the question: It often is advisable to NOT use KEYWORD_SET, but instead resort to a type query:

IF SIZE(variable, /TNAME) EQ 'UNDEFINED' THEN $
  variable = 'default value'

It has the advantage that you can actually check for the correct type of the keyword and handle unexpected or even different variable types:

IF SIZE(variable, /TNAME) NE 'LONG' THEN BEGIN
  IF SIZE(variable, /TNAME) EQ 'STRING' THEN $
    PRINT, "We need a number here... sure that the cast to LONG works?"
  variable = LONG(variable)
ENDIF

Upvotes: 1

honeste_vivere
honeste_vivere

Reputation: 298

After compiling the routine, type something like

get_this_done,KEYWORD1=1b

where the b after the one sets the numeric value to a BYTE type integer (also equivalent to TRUE). That should cause the y-variable to be printed to the screen.

The KEYWORD_SET function will return a TRUE for lots of different types of inputs that are basically either defined or not zero. The IF loop executes when the argument is TRUE.

Upvotes: 1

Related Questions