Search code examples
for-loopidl-programming-language

IDL for loop inconsistency

I recently came across this apparent inconsistency when going through someone's IDL code:

IDL> for i=0.,1.9,1. do print,i
      0.00000
      1.00000
IDL> for i=0.,1.9,1 do print,i
      0.00000
      1.00000
IDL> for i=0.,1.9 do print,i
      0.00000
      1.00000
      2.00000

Could anyone explain if there is a logic behind the behaviour in the third loop.

The IDL version used is 8.2.0.

(Note that my own code would stick to using integers in a for loop, and definitely after finding this.)

Solution

  • This might be a bug in IDL 8.2 - when I run the commands in version 8.2.1 I get the same behaviour as you. When I run them on a different computer with version 8.0 I get the expected behaviour, i.e. each command gives the same output. The inbuilt IDL help certainly suggests that they should all give the same output.