does emacs has rational number data type

Question

I eval a lisp expression in scratch

(+ (/ 1 2) (/ 1 2))

I got a 0.

normally it should be 1.

Answer 1

As Oleg points out, operators usually default to integer arithmetic unless you include floating point arguments (like 1.0).

With respect to your question about rational number support, emacs-calc (which is part of emacs) supports many number types including fractions (i.e. rational numbers), complex numbers, infinite precision integers, etc. Your code must call emacs-calc functions (instead of /, etc.) in order to use calc's arithmetic.

GNU Emacs Calc Manual:

• Fractions
• Index of Lisp Math Functions