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for variable = start_value , stop_value [ , increment ] do statement
( I use [ ] to indicate that increment is optional.) e.g.
IDL> for i = 0,10 do print,i
0
1
2
3 etc
IDL> for j=0,6,2 do print,j
0
2
4
6
; OR
for i = 0,10 do begin
print,i
print,i+2
endfor
( I use [ ] to indicate that increment is optional.)
Warnings:
- The loop variable takes its type from the start
value. This is a (short) integer in these examples. This means that
for j=0,40000 do .... will NOT do what you expect, but for
j=long(0),40000 do .... will be OK.
- Loops are slow, but are still sometimes the best way to do things
(and not actually the root of all evil)
John Marsham
2009-12-07