CODEWITHSUNDEEP
mainframepl-i
Nupur
Nupur

Reputation: 89

pl1 ROUND function for negative precision

In pl1 ROUND(expression1, expression2) function, if expression2 is negative how does rounding happen? For VALC=ROUND(17.126,-1) , what would be the result?

Upvotes: 0

Views: 72

Answers (1)

cschneid
cschneid

Reputation: 10765

From the IBM documentation for Enterprise PL/I for z/OS, where n corresponds to expresson2 in your question...

If n is greater than 0, rounding occurs at the (n)th digit to the right of the point. If n is zero or negative, rounding occurs at the (1-n)th digit to the left of the point.

I recommend becoming familiar with the IBM documentation for their products you use. At the top of the linked page there is a link for "All products" which will take you to a page of, unsurprisingly, all the extant IBM products and links to their documentation.

Edit in reply to comment seeking clarification...

I did see this documentation but failed to arrive at the result. In the case of my example, rounding will occur at the 2nd digit to left of decimal point, meaning ? what will be the output and how? it is confusing to me !

I would expect the result to be 20.

From the IBM documentation, lightly edited by adding "^" to indicate "to the power of"...

The value of the result is given by the following formula, where b = 10 if x is DECIMAL: round(x,n) = sign(x)*(b^-n)* floor(abs(x)* (b^n) + 1/2)

round(17.126,-1) = +1 * 10^-(-1) * floor(abs(17.126) * (10^-1) + 1/2)

= 10 * floor(17.126 * 0.1 + 1/2)
= 10 * floor(1.7126 + 1/2)
= 10 * floor(2.2126)
= 10 * 2
= 20

Upvotes: 3

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