pro ex2
 
; This program demonstrates some of the syntax of IDL

 
; Example of using strings:
name = ''                       ;initiallize the variable name
read,'Type your name: ',name
help,name                       ;get info on that variable
nickname = strmid(name,0,3)     ; get first 3 letter of name
print,'Can I call you ',nickname,' for short?'  
wait,3  & print                ;pause

; Define some arrays:

x = [0,1,2,4,5]      ; generate an array of integers
x = indgen(10)                 ; A simpler way to do this.
y = findgen(10)                ; an array of FLOAT ing point numbers

help,x,y         


;                FOR LOOPS

N = n_elements(x)               ; number of elements

;  A simple for loop: define y to be the square of x

for j = 0,N-1  do y(j) = x(j)^2 

;(However in IDL for loops are often unnecessary.  You can operate on
;the whole array at once eg,

y = x ^ 2

;  for loops can included many statements:

for i = 0, N-1 do begin
   print,'Index: ',i
   print,'Square: ',i^2
   print,'Root: ',sqrt(i)
endfor

;   WHILE LOOPS / IF THEN STATEMENTS

number  = fix(randomu(seed)*10) + 1                 ; random between 1 and 10
print, "I'm thinking of a number between 1 and 10"  ; note the ' ""
guess = 0                                            ; default
while guess ne number do begin
   read,'Guess: ',guess
   if number gt guess then print,'Higher' else print,'Lower'
endwhile

print, 'You got it!'

;  REPEAT/UNTIL   &  CASE STATEMENT  --you can skip this to start.
; (an less used alternative to IF/THEN is the CASE statement )

print,"Let's try another: "
number  = fix(randomu(seed)*10) + 1    

repeat begin
    read,'Guess: ',guess
    case 1 of 
        guess gt number: print,'Lower'
        guess lt number: print,'Higher'
        guess eq number: print,'GOT IT!' 
    endcase
endrep until guess eq number

end                             ;all good things must.