In recent versions of ksh, you can compare integer and floating point values with both [ expr ] and [[ expr ]], but there are no >= or <= operators and < and > in [[ expr ]] comparisons are for comparing string values, not arithmetic values.

The suggested changes zaxxon proposed in the code tags should work fine when using a ksh version newer than 1988, but keep the -ge and -lt rather than trying to use >= and < for arithmetic comparisons.