;+
; NAME:
;     im
; PURPOSE:
;     Return the imaginary part of a number
; EXPLANATION:
; CALLING SEQUENCE
;     r = im(x)
; INPUTS:
;     X - number or array of type complex, dcomplex
;         (other types returned as 0)
; OUTPUT:
;     result - imaginary part of x
;        float for x is complex
;        double for x is dcomplex
;        original type for all others
; METHOD:
;     IDL routines float and dfloat;
; REVISION HISTORY:
;     2012-01-08 Leslie Young, SwRI
;-
function im,x
    On_error,2

    res = size(x, /tname)
    ; use switch to "fall through" to the next statement
    ; making the byte, int etc simpler
    switch res of
       'COMPLEX': return, float(complex(0,-1.)*x)
       'DCOMPLEX': return, double(dcomplex(0,-1.)*x)
       'BYTE': 
       'INT': 
       'LONG': 
       'FLOAT': 
       'DOUBLE': 
       'UNIT': 
       'ULONG': 
       'LONG64': 
       'ULONG64': return, 0b*x    
       else : message,'Struct expression not allowed in this context.'
    endswitch
    
 end