Min And Max Of Tokens In A String

(Originally posted 2013-07-14.)

A couple of days ago I had a need to take a REXX string comprising space-separated numbers and find their minimum and maximum values. Here’s the technique I used.

(When I say “space-separated” there can be one or more spaces between the numbers, but there has to be at least one.)

The solution has three components:

1. The REXX SPACE function – to turn the list into a comma-separated string of numbers. (The second parameter is the number of so-called spaces to separate tokens with. The third is the actual character to use – in my case a comma.)
2. The REXX MIN (or MAX) function to compute the minimum (or maximum) value from this comma-separated string. These functions take a set of parameters of arbitrary length and do the maths on them. Parameters are separated by commas, hence the need to use SPACE to make it so.
3. INTERPRET to glue 1 and 2 together.

My need is relatively low volume, so the “health warning” about INTERPRET’s performance is hardly relevant for my use case.

Here’s the code:

/* Return min and max value of string of space-separated numbers */
minAndMax: procedure 
parse arg list 
comma_list=space(list,,",") 
interpret "minimum=min("comma_list")" 
interpret "maximum=max("comma_list")" 
return minimum maximum 

It’s relatively straightforward, taking a list of numbers and returning the minimum and maximum. You’ll notice it doesn’t check that the tokens really are numbers. If I were to extend it I’d probably check for two SLR conditions: Overflow (“*” or similar) and Missing Value (“—” or similar). I’d probably take some of the “List Comprehension” stuff I talked about in Dragging REXX Into The 21st Century? and apply it to the list.

And my code uses this to decide if I have a range of values or just a single one. In the former case it turns the pair of numbers into e.g. “1-5” and the latter just e.g. “4”.

Of course there are other ways to do minimum and maximum for a list of numbers but this one seems the simplest and most elegant to me. “6 months later me” might take a different view. 🙂