TIP #299 Version 1.3: Add isqrt() Math Function

This is not necessarily the current version of this TIP.

Abstract

This TIP proposes a new expr math function isqrt().

Background

With the advent of large integers, Tcl supports taking the square roots of arguments that lie outside the native floating-point range of the machine. The square roots are returned as floating point numbers if possible. This behaviour is correct when floating-point calculations are intended. There are times, however, when an arbitrary-precision square root is wanted. This root cannot be obtained by evaluating entier(sqrt($n)), because sqrt($n) has already lost precision.

Proposed Change

This TIP proposes adding a new math function, isqrt($n), that will return the integer part of the square root of $n to arbitrary precision. The argument $n must be numeric and non-negative; it may be either integer or floating-point.

Reference Implementation

Tcl Feature Request #1602534 contains a complete reference implementation for the isqrt function.

Copyright

This document has been placed in the public domain.

This is not necessarily the current version of this TIP.