<div dir="ltr"><div>Faster version:<br></div><div><br></div><div>instance (Integral a, PrintfArg a) => PrintfArg (Ratio a) where</div> formatArg x f@(FieldFormat w p a s l _ c) = if elem c "gGv"<br> then let<br> d = " % " ++ formatArg (denominator x) (FieldFormat Nothing Nothing Nothing s l "" 'd') ""<br> (w',a') = case a of<br> Just LeftAdjust -> (Nothing, Nothing)<br> _ -> (fmap (subtract (length d)) w, a)<br> n = formatArg (numerator x) (f {fmtWidth = w', fmtAdjust = a', fmtChar = 'd'}) ""<br> in formatArg (n ++ d) (f {fmtPrecision = Nothing, fmtChar = 's'})<br> else if elem c "doxXb"<br> then formatArg (round x :: Integer) f<br> else case p of <br> Nothing -> error "Text.Printf.formatArg: precision not given"<br> Just p' -> if p' <= 0<br> then formatArg x (f {fmtPrecision = Nothing, fmtChar = 'd'})<br> else if elem c "fF"<br> then let<br> n = truncate x<br> sig = '.' : formatArg (round ((x - fromInteger n) * 10^p') :: Integer) (FieldFormat Nothing Nothing Nothing Nothing False "" 'd') ""<br> (w',a') = case a of<br> Just LeftAdjust -> (Nothing, Nothing)<br> _ -> (fmap (subtract (length sig)) w, a)<br> b = formatArg n (FieldFormat w' Nothing a' s l "" 'd') ""<br> in formatArg (b ++ sig) (f {fmtPrecision = Nothing, fmtChar = 's'})<br> else if elem c "eE"<br> then let<br> (q,e) = log10 x<br> sig = c : show e<br> (w',a') = case a of<br> Just LeftAdjust -> (Nothing, Nothing)<br> _ -> (fmap (subtract (length sig)) w, a)<br> fp = formatArg q (f {fmtWidth = w', fmtAdjust = a', fmtChar = 'f'}) ""<br> in formatArg (fp ++ sig) (f {fmtPrecision = Nothing, fmtChar = 's'})<br> else error "Text.Printf.formatArg: bad format character"<br> where<br> goF _ 0 = ""<br> goF x p = case compare x 0 of<br> LT -> '-' : goF (negate x) p<br> EQ -> "0"<br> GT -> if 1 == p<br> then show (round (10 * x) :: Integer)<br> else let<br> x10 = 10 * x<br> n = truncate x10<br> in show n ++ goF (x10 - fromIntegral n) (p - 1)<br> log10 x<br> | x < 1 = let<br> (q,e) = log10 (x * 10)<br> in (q, e - 1)<br> | 10 <= x = let<br> (q,e) = log10 (x / 10)<br> in (q, e + 1)<br> | otherwise = (x, 0)<br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">2020년 2월 8일 (토) 오전 8:40, Dannyu NDos <<a href="mailto:ndospark320@gmail.com">ndospark320@gmail.com</a>>님이 작성:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><br><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">---------- Forwarded message ---------<br>보낸사람: <b class="gmail_sendername" dir="auto">Dannyu NDos</b> <span dir="auto"><<a href="mailto:ndospark320@gmail.com" target="_blank">ndospark320@gmail.com</a>></span><br>Date: 2020년 2월 8일 (토) 오전 8:22<br>Subject: Re: add instance PrintfArg Ratio<br>To: Henning Thielemann <<a href="mailto:lemming@henning-thielemann.de" target="_blank">lemming@henning-thielemann.de</a>><br></div><br><br><div dir="ltr"><div>In that case, here (with some bugfixes):</div><div><br></div><div>instance (Integral a, PrintfArg a) => PrintfArg (Ratio a) where<br> formatArg x f@(FieldFormat w p a s l _ c) = if elem c "gGv"<br> then let<br> d = " % " ++ formatArg (denominator x) (FieldFormat Nothing Nothing Nothing s l "" 'd') ""<br> (w',a') = case a of<br> Just LeftAdjust -> (Nothing, Nothing)<br> _ -> (fmap (subtract (length d)) w, a)<br> n = formatArg (numerator x) (f {fmtWidth = w', fmtAdjust = a', fmtChar = 'd'}) ""<br> in formatArg (n ++ d) (f {fmtPrecision = Nothing, fmtChar = 's'})<br> else if elem c "doxXb"<br> then formatArg (round x :: Integer) f<br> else case p of <br> Nothing -> error "Text.Printf.formatArg: precision not given"<br> Just p' -> if p' <= 0<br> then formatArg x (f {fmtPrecision = Nothing, fmtChar = 'd'})<br> else if elem c "fF"<br> then let<br> n = truncate x<br> sig = '.' : goF (x - fromInteger n) p'<br> (w',a') = case a of<br> Just LeftAdjust -> (Nothing, Nothing)<br> _ -> (fmap (subtract (length sig)) w, a)<br> b = formatArg n (FieldFormat w' Nothing a' s l "" 'd') ""<br> in formatArg (b ++ sig) (f {fmtPrecision = Nothing, fmtChar = 's'})<br> else if elem c "eE"<br> then let<br> (q,e) = log10 x<br> sig = c : show e<br> (w',a') = case a of<br> Just LeftAdjust -> (Nothing, Nothing)<br> _ -> (fmap (subtract (length sig)) w, a)<br> fp = formatArg q (f {fmtWidth = w', fmtAdjust = a', fmtChar = 'f'}) ""<br> in formatArg (fp ++ sig) (f {fmtPrecision = Nothing, fmtChar = 's'})<br> else error "Text.Printf.formatArg: bad format character"<br> where<br> goF _ 0 = ""<br> goF x p = case compare x 0 of<br> LT -> '-' : goF (negate x) p<br> EQ -> "0"<br> GT -> if 1 == p<br> then show (round (10 * x) :: Integer)<br> else let<br> x10 = 10 * x<br> n = truncate x10<br> in show n ++ goF (x10 - fromIntegral n) (p - 1)<br> log10 x<br> | x < 1 = let<br> (q,e) = log10 (x * 10)<br> in (q, e - 1)<br> | 10 <= x = let<br> (q,e) = log10 (x / 10)<br> in (q, e + 1)<br> | otherwise = (x, 0)<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">2020년 2월 8일 (토) 오전 6:44, Henning Thielemann <<a href="mailto:lemming@henning-thielemann.de" target="_blank">lemming@henning-thielemann.de</a>>님이 작성:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><br>
On Fri, 7 Feb 2020, Dannyu NDos wrote:<br>
<br>
> It just is so convenient.<br>
> <br>
> instance (Integral a, Show a) => PrintfArg (Ratio a) where<br>
<br>
Why should a Printf instance be base on Show? Wouldn't it better to format <br>
numerator and denominator using printf, too?<br>
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