What are real numbers in Dafny?

Question

What are real numbers in Dafny. Are they represented as IEEE 754-2008 floating point numbers? If not, then what are they? I.e., what is the specification of the real type in Dafny?

if you find an answer helpful, please upvote it, and accept the one that is best. see https://stackoverflow.com/help/someone-answers — James Wilcox, Feb 11 '18 at 22:25

score 4 · Accepted Answer · answered Jan 29 '18 at 20:52

Dafny's real numbers are not floating point numbers.

From a verification perspective, they are the mathematical real numbers, and Dafny reasons about them using Z3's theory of real arithmetic.

From a compilation perspective, Dafny actually compiles them to BigRationals, which is made possible by the fact that Dafny doesn't have any builtin operations for creating irrational real numbers.

What are real numbers in Dafny?

1 Answers1