Subject: Re: format floats with commas - why not? From: Erik Naggum <firstname.lastname@example.org> Date: 1997/08/12 Newsgroups: comp.lang.lisp Message-ID: <email@example.com> * firstname.lastname@example.org | So: I can format a number with commification only with ~d (and ~r, ~b, | ~o, ~x, as per CLtL2 22.3.3 p 585), but not with ~f or ~$. What is the | reason for not having commification with floats? It would seem only | natural to print large numbers like $1234567.89 as $1,234,567.89. here's a shot. (format nil "~/dollars/" 123456789.87) => "$123,456,792.00" (format nil "~/dollars/" 123456789.87d0) => "$123,456,789.87" (format nil "~/dollars/" 12345678987/100) => "$123,456,789.87" note that 123456789.87 requires more significant bits than are available in single-precision floats and that we suffer massive loss of precision in floating point computations. however, this function handles rationals correctly, which the ~$ format control is not guaranteed to do, as in: (format nil "~$" 123456789.87) => "123456790.00" (format nil "~$" 123456789.87d0) => "123456789.87" (format nil "~$" 12345678987/100) => "123456790.00" (defun dollars (stream amount colon-p atsign-p &optional (width 0) padchar commachar) "Print an amount of dollars for humans to read. The full form is ~width,padchar,commachar:@/dollars/, where width is the minimum width of the field (default 0), padchar is the character used to pad to the width on the left end, and commachar is the separator between each group of three digits. The @ modifier controls printing of the sign of positive amounts. If omitted, a positive value prints without a sign. Otherwise, a positive amount has an explicit + sign. The : modifier controls the position of the sign and the padding. If omitted, the dollar sign is printed in the leftmost position, then any intervening pad characters, then the signed value. Otherwise, the sign occupies the leftmost position, and the dollar sign follows any intervening padchars. Copyright 1997 by Erik Naggum. Any use is permitted provided that this copyright notice is retained and that all changes are duly identified." (let* ((digits (multiple-value-bind (dollars cents) (floor (abs amount) 1) (format nil "~,,V:D.~2,'0D" commachar dollars (round cents 0.01)))) (sign (if (minusp amount) #\- (if atsign-p #\+ nil))) (padding (max 0 (- width 1 (if sign 1 0) (length digits))))) (format stream "~@[~C~]~V,,,VA~@[~C~]~A" (if colon-p sign #\$) padding padchar "" (if colon-p #\$ sign) digits))) #\Erik -- 404 Give me a URL I cannot refuse.