[PATCH] Add Roman numerals in *printf

[PATCH] Add Roman numerals in *printf

[Matteo Croce]

Since Fibonacci adoption in the 13th century, Arabic numbers have become
the standard numeric system used in every culture.
However, older numeral systems are yet used in many contexts,
for example, ancient Roman numerals are often used to represent
software version, protocol revision or even movie chapters.

This patch adds the `%r' modifier in all the *printf functions,
which can be used to represent a number in Roman numerals.
This has two big advantages:

first of all there is no need to hardcode text strings in
the code which needs to be updated on every version change.
e.g. printf("System V booting") or printf("Text Editor for OS X")
can be replaced with:
printf("System %R booting", ver) and printf("Text Editor for OS %R", ver)
and the right version string is generated at runtime.

The second advantage is that Roman numerals are very lengthy and even a small
16 bit number can occupy up to 15 bytes,
thus leading to a 650% increase in code size.

For a technical limitation the maximum number that can be represented in Roman
numerals are limited to 3999, but archaeologist agrees that ancient Romans uses
a superscript to multiply by 1000 and a vertical line to multiply to 1 million.

To avoid using Unicode characters in such basic IO routines, a pair of _ are
used to represent a thousand value, e.g. _XX_ for 20 000
and a | to represent millions, e.g. |L| for 50 000 000. This increase the
maximum integer that can be represented to 499 999 999 which should be
a reasonable value for our concern, bigger numbers will print as `(infinitum)'

Another issue is the zero value which was missing in the Roman system,
indeed the zero sign was "imported" by Fibonacci from North Africa,
so when trying to print 0 as Roman numeral, the string `(nihil)',
which is the Latin word for `nothing', will printed like `(null)` for pointers.

Roman numerals can be generated both in upper and lower case
respectively, with the `%R' and `%r' modifier.
---
 stdio-common/vfprintf.c | 109 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 93 insertions(+), 16 deletions(-)

diff --git a/stdio-common/vfprintf.c b/stdio-common/vfprintf.c
index 6829d4d..e85c29c 100644
--- a/stdio-common/vfprintf.c
+++ b/stdio-common/vfprintf.c
@@ -215,20 +215,20 @@ static const uint8_t jump_table[] =
     /* '4' */  8, /* '5' */  8, /* '6' */  8, /* '7' */  8,
     /* '8' */  8, /* '9' */  8,            0,            0,
 	       0,            0,            0,            0,
-	       0, /* 'A' */ 26,            0, /* 'C' */ 25,
-	       0, /* 'E' */ 19, /* F */   19, /* 'G' */ 19,
-	       0, /* 'I' */ 29,            0,            0,
+	       0, /* 'A' */ 27,            0, /* 'C' */ 26,
+	       0, /* 'E' */ 20, /* F */   20, /* 'G' */ 20,
+	       0, /* 'I' */ 30,            0,            0,
     /* 'L' */ 12,            0,            0,            0,
-	       0,            0,            0, /* 'S' */ 21,
+	       0,            0, /* 'R' */ 19, /* 'S' */ 22,
 	       0,            0,            0,            0,
     /* 'X' */ 18,            0, /* 'Z' */ 13,            0,
 	       0,            0,            0,            0,
-	       0, /* 'a' */ 26,            0, /* 'c' */ 20,
-    /* 'd' */ 15, /* 'e' */ 19, /* 'f' */ 19, /* 'g' */ 19,
-    /* 'h' */ 10, /* 'i' */ 15, /* 'j' */ 28,            0,
-    /* 'l' */ 11, /* 'm' */ 24, /* 'n' */ 23, /* 'o' */ 17,
-    /* 'p' */ 22, /* 'q' */ 12,            0, /* 's' */ 21,
-    /* 't' */ 27, /* 'u' */ 16,            0,            0,
+	       0, /* 'a' */ 27,            0, /* 'c' */ 21,
+    /* 'd' */ 15, /* 'e' */ 20, /* 'f' */ 20, /* 'g' */ 20,
+    /* 'h' */ 10, /* 'i' */ 15, /* 'j' */ 29,            0,
+    /* 'l' */ 11, /* 'm' */ 25, /* 'n' */ 24, /* 'o' */ 17,
+    /* 'p' */ 23, /* 'q' */ 12, /* 'r' */ 19, /* 's' */ 22,
+    /* 't' */ 28, /* 'u' */ 16,            0,            0,
     /* 'x' */ 18,            0, /* 'z' */ 13
   };
 
@@ -269,7 +269,7 @@ static const uint8_t jump_table[] =
 
 #define STEP0_3_TABLE							      \
     /* Step 0: at the beginning.  */					      \
-    static JUMP_TABLE_TYPE step0_jumps[30] =				      \
+    static JUMP_TABLE_TYPE step0_jumps[31] =				      \
     {									      \
       REF (form_unknown),						      \
       REF (flag_space),		/* for ' ' */				      \
@@ -290,6 +290,7 @@ static const uint8_t jump_table[] =
       REF (form_unsigned),	/* for 'u' */				      \
       REF (form_octal),		/* for 'o' */				      \
       REF (form_hexa),		/* for 'X', 'x' */			      \
+      REF (form_roman),		/* for 'R', 'r' */			      \
       REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
       REF (form_character),	/* for 'c' */				      \
       REF (form_string),	/* for 's', 'S' */			      \
@@ -303,7 +304,7 @@ static const uint8_t jump_table[] =
       REF (flag_i18n),		/* for 'I' */				      \
     };									      \
     /* Step 1: after processing width.  */				      \
-    static JUMP_TABLE_TYPE step1_jumps[30] =				      \
+    static JUMP_TABLE_TYPE step1_jumps[31] =				      \
     {									      \
       REF (form_unknown),						      \
       REF (form_unknown),	/* for ' ' */				      \
@@ -324,6 +325,7 @@ static const uint8_t jump_table[] =
       REF (form_unsigned),	/* for 'u' */				      \
       REF (form_octal),		/* for 'o' */				      \
       REF (form_hexa),		/* for 'X', 'x' */			      \
+      REF (form_roman),		/* for 'R', 'r' */			      \
       REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
       REF (form_character),	/* for 'c' */				      \
       REF (form_string),	/* for 's', 'S' */			      \
@@ -337,7 +339,7 @@ static const uint8_t jump_table[] =
       REF (form_unknown)        /* for 'I' */				      \
     };									      \
     /* Step 2: after processing precision.  */				      \
-    static JUMP_TABLE_TYPE step2_jumps[30] =				      \
+    static JUMP_TABLE_TYPE step2_jumps[31] =				      \
     {									      \
       REF (form_unknown),						      \
       REF (form_unknown),	/* for ' ' */				      \
@@ -358,6 +360,7 @@ static const uint8_t jump_table[] =
       REF (form_unsigned),	/* for 'u' */				      \
       REF (form_octal),		/* for 'o' */				      \
       REF (form_hexa),		/* for 'X', 'x' */			      \
+      REF (form_roman),		/* for 'R', 'r' */			      \
       REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
       REF (form_character),	/* for 'c' */				      \
       REF (form_string),	/* for 's', 'S' */			      \
@@ -371,7 +374,7 @@ static const uint8_t jump_table[] =
       REF (form_unknown)        /* for 'I' */				      \
     };									      \
     /* Step 3a: after processing first 'h' modifier.  */		      \
-    static JUMP_TABLE_TYPE step3a_jumps[30] =				      \
+    static JUMP_TABLE_TYPE step3a_jumps[31] =				      \
     {									      \
       REF (form_unknown),						      \
       REF (form_unknown),	/* for ' ' */				      \
@@ -392,6 +395,7 @@ static const uint8_t jump_table[] =
       REF (form_unsigned),	/* for 'u' */				      \
       REF (form_octal),		/* for 'o' */				      \
       REF (form_hexa),		/* for 'X', 'x' */			      \
+      REF (form_roman),		/* for 'R', 'r' */			      \
       REF (form_unknown),	/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
       REF (form_unknown),	/* for 'c' */				      \
       REF (form_unknown),	/* for 's', 'S' */			      \
@@ -405,7 +409,7 @@ static const uint8_t jump_table[] =
       REF (form_unknown)        /* for 'I' */				      \
     };									      \
     /* Step 3b: after processing first 'l' modifier.  */		      \
-    static JUMP_TABLE_TYPE step3b_jumps[30] =				      \
+    static JUMP_TABLE_TYPE step3b_jumps[31] =				      \
     {									      \
       REF (form_unknown),						      \
       REF (form_unknown),	/* for ' ' */				      \
@@ -426,6 +430,7 @@ static const uint8_t jump_table[] =
       REF (form_unsigned),	/* for 'u' */				      \
       REF (form_octal),		/* for 'o' */				      \
       REF (form_hexa),		/* for 'X', 'x' */			      \
+      REF (form_roman),		/* for 'R', 'r' */			      \
       REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
       REF (form_character),	/* for 'c' */				      \
       REF (form_string),	/* for 's', 'S' */			      \
@@ -441,7 +446,7 @@ static const uint8_t jump_table[] =
 
 #define STEP4_TABLE							      \
     /* Step 4: processing format specifier.  */				      \
-    static JUMP_TABLE_TYPE step4_jumps[30] =				      \
+    static JUMP_TABLE_TYPE step4_jumps[31] =				      \
     {									      \
       REF (form_unknown),						      \
       REF (form_unknown),	/* for ' ' */				      \
@@ -462,6 +467,7 @@ static const uint8_t jump_table[] =
       REF (form_unsigned),	/* for 'u' */				      \
       REF (form_octal),		/* for 'o' */				      \
       REF (form_hexa),		/* for 'X', 'x' */			      \
+      REF (form_roman),		/* for 'R', 'r' */			      \
       REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
       REF (form_character),	/* for 'c' */				      \
       REF (form_string),	/* for 's', 'S' */			      \
@@ -741,6 +747,11 @@ static const uint8_t jump_table[] =
 	  break;							      \
 	}								      \
 									      \
+    LABEL (form_roman):							      \
+      /* Ancient Roman / Latin number. */				      \
+      roman(s, va_arg (ap, int), spec == L_('R'));			      \
+      break;							              \
+									      \
     LABEL (form_float):							      \
       {									      \
 	/* Floating-point number.  This is handled by printf_fp.c.  */	      \
@@ -1210,6 +1221,72 @@ static const uint8_t jump_table[] =
       break;
 #endif
 
+static const int numbers[] = { 1000, 900, 500, 400, 100, 90,
+			       50, 40, 10, 9, 5, 4, 1 };
+static const CHAR_T *_rul[] = { L_("M"), L_("CM"), L_("D"), L_("CD"), L_("C"),
+			      L_("XC"), L_("L"), L_("XL"), L_("X"),
+			      L_("IX"), L_("V"), L_("IV"), L_("I") };
+static const CHAR_T *_rll[] = { L_("m"), L_("cm"), L_("d"), L_("cd"), L_("c"),
+			      L_("xc"), L_("l"), L_("xl"), L_("x"),
+			      L_("ix"), L_("v"), L_("iv"), L_("i") };
+
+static void roman(FILE *s, long int num, int upper_case)
+{
+  /* used by outchar */
+  int done = 0;
+
+  const CHAR_T **letters = upper_case ? _rul : _rll;
+
+  if(!num)
+    {
+      outstring(L_("(nihil)"), 7);
+      return;
+    }
+
+  if(num < 0)
+    {
+      outchar(L_('-'));
+      num = -num;
+    }
+
+  if(num > 499999999)
+    {
+      outstring(L_("(infinitum)"), 11);
+      return;
+    }
+
+  if(num > 99999)
+    {
+      outchar(L_('|'));
+      roman(s, num / 100000, upper_case);
+      outchar(L_('|'));
+      num %= 100000;
+    }
+
+  if(num > 4999)
+    {
+      outchar(L_('_'));
+      roman(s, num / 1000, upper_case);
+      outchar(L_('_'));
+      num %= 1000;
+    }
+
+  for (int i = 0; i < sizeof(numbers) / sizeof(*numbers); i++)
+    {
+      while (num >= numbers[i])
+	{
+	  outchar(letters[i][0]);
+	  if(letters[i][1])
+	  outchar(letters[i][1]);
+	  num -= numbers[i];
+	}
+    }
+
+  /* suppress warnings */
+  all_done:
+  return;
+}
+
 /* Helper function to provide temporary buffering for unbuffered streams.  */
 static int buffered_vfprintf (FILE *stream, const CHAR_T *fmt, va_list)
      __THROW __attribute__ ((noinline)) internal_function;
-- 
2.5.0

Re: [PATCH] Add Roman numerals in *printf

[Adhemerval Zanella]

AFAIK this format is not defined in any standard or specification GLIBC
follows neither I think it is worth an GNU extension.  There are some
problems in adding an intrinsic modifier that are not supported in
others platforms: compatibility, the modifier can be defined in a future
POSIX standard, how to enable (with _GNU_SOURCE of something), etc.

You can implement it as printf customization [1], which is far from
perfect but with some care gets the job done.

[1] http://www.gnu.org/software/libc/manual/html_node/Customizing-Printf.html


On 01-04-2016 06:33, Matteo Croce wrote:
> Since Fibonacci adoption in the 13th century, Arabic numbers have become
> the standard numeric system used in every culture.
> However, older numeral systems are yet used in many contexts,
> for example, ancient Roman numerals are often used to represent
> software version, protocol revision or even movie chapters.
> 
> This patch adds the `%r' modifier in all the *printf functions,
> which can be used to represent a number in Roman numerals.
> This has two big advantages:
> 
> first of all there is no need to hardcode text strings in
> the code which needs to be updated on every version change.
> e.g. printf("System V booting") or printf("Text Editor for OS X")
> can be replaced with:
> printf("System %R booting", ver) and printf("Text Editor for OS %R", ver)
> and the right version string is generated at runtime.
> 
> The second advantage is that Roman numerals are very lengthy and even a small
> 16 bit number can occupy up to 15 bytes,
> thus leading to a 650% increase in code size.
> 
> For a technical limitation the maximum number that can be represented in Roman
> numerals are limited to 3999, but archaeologist agrees that ancient Romans uses
> a superscript to multiply by 1000 and a vertical line to multiply to 1 million.
> 
> To avoid using Unicode characters in such basic IO routines, a pair of _ are
> used to represent a thousand value, e.g. _XX_ for 20 000
> and a | to represent millions, e.g. |L| for 50 000 000. This increase the
> maximum integer that can be represented to 499 999 999 which should be
> a reasonable value for our concern, bigger numbers will print as `(infinitum)'
> 
> Another issue is the zero value which was missing in the Roman system,
> indeed the zero sign was "imported" by Fibonacci from North Africa,
> so when trying to print 0 as Roman numeral, the string `(nihil)',
> which is the Latin word for `nothing', will printed like `(null)` for pointers.
> 
> Roman numerals can be generated both in upper and lower case
> respectively, with the `%R' and `%r' modifier.
> ---
>  stdio-common/vfprintf.c | 109 +++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 93 insertions(+), 16 deletions(-)
> 
> diff --git a/stdio-common/vfprintf.c b/stdio-common/vfprintf.c
> index 6829d4d..e85c29c 100644
> --- a/stdio-common/vfprintf.c
> +++ b/stdio-common/vfprintf.c
> @@ -215,20 +215,20 @@ static const uint8_t jump_table[] =
>      /* '4' */  8, /* '5' */  8, /* '6' */  8, /* '7' */  8,
>      /* '8' */  8, /* '9' */  8,            0,            0,
>  	       0,            0,            0,            0,
> -	       0, /* 'A' */ 26,            0, /* 'C' */ 25,
> -	       0, /* 'E' */ 19, /* F */   19, /* 'G' */ 19,
> -	       0, /* 'I' */ 29,            0,            0,
> +	       0, /* 'A' */ 27,            0, /* 'C' */ 26,
> +	       0, /* 'E' */ 20, /* F */   20, /* 'G' */ 20,
> +	       0, /* 'I' */ 30,            0,            0,
>      /* 'L' */ 12,            0,            0,            0,
> -	       0,            0,            0, /* 'S' */ 21,
> +	       0,            0, /* 'R' */ 19, /* 'S' */ 22,
>  	       0,            0,            0,            0,
>      /* 'X' */ 18,            0, /* 'Z' */ 13,            0,
>  	       0,            0,            0,            0,
> -	       0, /* 'a' */ 26,            0, /* 'c' */ 20,
> -    /* 'd' */ 15, /* 'e' */ 19, /* 'f' */ 19, /* 'g' */ 19,
> -    /* 'h' */ 10, /* 'i' */ 15, /* 'j' */ 28,            0,
> -    /* 'l' */ 11, /* 'm' */ 24, /* 'n' */ 23, /* 'o' */ 17,
> -    /* 'p' */ 22, /* 'q' */ 12,            0, /* 's' */ 21,
> -    /* 't' */ 27, /* 'u' */ 16,            0,            0,
> +	       0, /* 'a' */ 27,            0, /* 'c' */ 21,
> +    /* 'd' */ 15, /* 'e' */ 20, /* 'f' */ 20, /* 'g' */ 20,
> +    /* 'h' */ 10, /* 'i' */ 15, /* 'j' */ 29,            0,
> +    /* 'l' */ 11, /* 'm' */ 25, /* 'n' */ 24, /* 'o' */ 17,
> +    /* 'p' */ 23, /* 'q' */ 12, /* 'r' */ 19, /* 's' */ 22,
> +    /* 't' */ 28, /* 'u' */ 16,            0,            0,
>      /* 'x' */ 18,            0, /* 'z' */ 13
>    };
>  
> @@ -269,7 +269,7 @@ static const uint8_t jump_table[] =
>  
>  #define STEP0_3_TABLE							      \
>      /* Step 0: at the beginning.  */					      \
> -    static JUMP_TABLE_TYPE step0_jumps[30] =				      \
> +    static JUMP_TABLE_TYPE step0_jumps[31] =				      \
>      {									      \
>        REF (form_unknown),						      \
>        REF (flag_space),		/* for ' ' */				      \
> @@ -290,6 +290,7 @@ static const uint8_t jump_table[] =
>        REF (form_unsigned),	/* for 'u' */				      \
>        REF (form_octal),		/* for 'o' */				      \
>        REF (form_hexa),		/* for 'X', 'x' */			      \
> +      REF (form_roman),		/* for 'R', 'r' */			      \
>        REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
>        REF (form_character),	/* for 'c' */				      \
>        REF (form_string),	/* for 's', 'S' */			      \
> @@ -303,7 +304,7 @@ static const uint8_t jump_table[] =
>        REF (flag_i18n),		/* for 'I' */				      \
>      };									      \
>      /* Step 1: after processing width.  */				      \
> -    static JUMP_TABLE_TYPE step1_jumps[30] =				      \
> +    static JUMP_TABLE_TYPE step1_jumps[31] =				      \
>      {									      \
>        REF (form_unknown),						      \
>        REF (form_unknown),	/* for ' ' */				      \
> @@ -324,6 +325,7 @@ static const uint8_t jump_table[] =
>        REF (form_unsigned),	/* for 'u' */				      \
>        REF (form_octal),		/* for 'o' */				      \
>        REF (form_hexa),		/* for 'X', 'x' */			      \
> +      REF (form_roman),		/* for 'R', 'r' */			      \
>        REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
>        REF (form_character),	/* for 'c' */				      \
>        REF (form_string),	/* for 's', 'S' */			      \
> @@ -337,7 +339,7 @@ static const uint8_t jump_table[] =
>        REF (form_unknown)        /* for 'I' */				      \
>      };									      \
>      /* Step 2: after processing precision.  */				      \
> -    static JUMP_TABLE_TYPE step2_jumps[30] =				      \
> +    static JUMP_TABLE_TYPE step2_jumps[31] =				      \
>      {									      \
>        REF (form_unknown),						      \
>        REF (form_unknown),	/* for ' ' */				      \
> @@ -358,6 +360,7 @@ static const uint8_t jump_table[] =
>        REF (form_unsigned),	/* for 'u' */				      \
>        REF (form_octal),		/* for 'o' */				      \
>        REF (form_hexa),		/* for 'X', 'x' */			      \
> +      REF (form_roman),		/* for 'R', 'r' */			      \
>        REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
>        REF (form_character),	/* for 'c' */				      \
>        REF (form_string),	/* for 's', 'S' */			      \
> @@ -371,7 +374,7 @@ static const uint8_t jump_table[] =
>        REF (form_unknown)        /* for 'I' */				      \
>      };									      \
>      /* Step 3a: after processing first 'h' modifier.  */		      \
> -    static JUMP_TABLE_TYPE step3a_jumps[30] =				      \
> +    static JUMP_TABLE_TYPE step3a_jumps[31] =				      \
>      {									      \
>        REF (form_unknown),						      \
>        REF (form_unknown),	/* for ' ' */				      \
> @@ -392,6 +395,7 @@ static const uint8_t jump_table[] =
>        REF (form_unsigned),	/* for 'u' */				      \
>        REF (form_octal),		/* for 'o' */				      \
>        REF (form_hexa),		/* for 'X', 'x' */			      \
> +      REF (form_roman),		/* for 'R', 'r' */			      \
>        REF (form_unknown),	/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
>        REF (form_unknown),	/* for 'c' */				      \
>        REF (form_unknown),	/* for 's', 'S' */			      \
> @@ -405,7 +409,7 @@ static const uint8_t jump_table[] =
>        REF (form_unknown)        /* for 'I' */				      \
>      };									      \
>      /* Step 3b: after processing first 'l' modifier.  */		      \
> -    static JUMP_TABLE_TYPE step3b_jumps[30] =				      \
> +    static JUMP_TABLE_TYPE step3b_jumps[31] =				      \
>      {									      \
>        REF (form_unknown),						      \
>        REF (form_unknown),	/* for ' ' */				      \
> @@ -426,6 +430,7 @@ static const uint8_t jump_table[] =
>        REF (form_unsigned),	/* for 'u' */				      \
>        REF (form_octal),		/* for 'o' */				      \
>        REF (form_hexa),		/* for 'X', 'x' */			      \
> +      REF (form_roman),		/* for 'R', 'r' */			      \
>        REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
>        REF (form_character),	/* for 'c' */				      \
>        REF (form_string),	/* for 's', 'S' */			      \
> @@ -441,7 +446,7 @@ static const uint8_t jump_table[] =
>  
>  #define STEP4_TABLE							      \
>      /* Step 4: processing format specifier.  */				      \
> -    static JUMP_TABLE_TYPE step4_jumps[30] =				      \
> +    static JUMP_TABLE_TYPE step4_jumps[31] =				      \
>      {									      \
>        REF (form_unknown),						      \
>        REF (form_unknown),	/* for ' ' */				      \
> @@ -462,6 +467,7 @@ static const uint8_t jump_table[] =
>        REF (form_unsigned),	/* for 'u' */				      \
>        REF (form_octal),		/* for 'o' */				      \
>        REF (form_hexa),		/* for 'X', 'x' */			      \
> +      REF (form_roman),		/* for 'R', 'r' */			      \
>        REF (form_float),		/* for 'E', 'e', 'F', 'f', 'G', 'g' */	      \
>        REF (form_character),	/* for 'c' */				      \
>        REF (form_string),	/* for 's', 'S' */			      \
> @@ -741,6 +747,11 @@ static const uint8_t jump_table[] =
>  	  break;							      \
>  	}								      \
>  									      \
> +    LABEL (form_roman):							      \
> +      /* Ancient Roman / Latin number. */				      \
> +      roman(s, va_arg (ap, int), spec == L_('R'));			      \
> +      break;							              \
> +									      \
>      LABEL (form_float):							      \
>        {									      \
>  	/* Floating-point number.  This is handled by printf_fp.c.  */	      \
> @@ -1210,6 +1221,72 @@ static const uint8_t jump_table[] =
>        break;
>  #endif
>  
> +static const int numbers[] = { 1000, 900, 500, 400, 100, 90,
> +			       50, 40, 10, 9, 5, 4, 1 };
> +static const CHAR_T *_rul[] = { L_("M"), L_("CM"), L_("D"), L_("CD"), L_("C"),
> +			      L_("XC"), L_("L"), L_("XL"), L_("X"),
> +			      L_("IX"), L_("V"), L_("IV"), L_("I") };
> +static const CHAR_T *_rll[] = { L_("m"), L_("cm"), L_("d"), L_("cd"), L_("c"),
> +			      L_("xc"), L_("l"), L_("xl"), L_("x"),
> +			      L_("ix"), L_("v"), L_("iv"), L_("i") };
> +
> +static void roman(FILE *s, long int num, int upper_case)
> +{
> +  /* used by outchar */
> +  int done = 0;
> +
> +  const CHAR_T **letters = upper_case ? _rul : _rll;
> +
> +  if(!num)
> +    {
> +      outstring(L_("(nihil)"), 7);
> +      return;
> +    }
> +
> +  if(num < 0)
> +    {
> +      outchar(L_('-'));
> +      num = -num;
> +    }
> +
> +  if(num > 499999999)
> +    {
> +      outstring(L_("(infinitum)"), 11);
> +      return;
> +    }
> +
> +  if(num > 99999)
> +    {
> +      outchar(L_('|'));
> +      roman(s, num / 100000, upper_case);
> +      outchar(L_('|'));
> +      num %= 100000;
> +    }
> +
> +  if(num > 4999)
> +    {
> +      outchar(L_('_'));
> +      roman(s, num / 1000, upper_case);
> +      outchar(L_('_'));
> +      num %= 1000;
> +    }
> +
> +  for (int i = 0; i < sizeof(numbers) / sizeof(*numbers); i++)
> +    {
> +      while (num >= numbers[i])
> +	{
> +	  outchar(letters[i][0]);
> +	  if(letters[i][1])
> +	  outchar(letters[i][1]);
> +	  num -= numbers[i];
> +	}
> +    }
> +
> +  /* suppress warnings */
> +  all_done:
> +  return;
> +}
> +
>  /* Helper function to provide temporary buffering for unbuffered streams.  */
>  static int buffered_vfprintf (FILE *stream, const CHAR_T *fmt, va_list)
>       __THROW __attribute__ ((noinline)) internal_function;
> 

Re: [PATCH] Add Roman numerals in *printf

[Carlos O'Donell]

On 04/01/2016 05:33 AM, Matteo Croce wrote:
> This patch adds the `%r' modifier in all the *printf functions,
> which can be used to represent a number in Roman numerals.
> This has two big advantages:

High-level review:

(a) Standardize '%r' and '%R' first.

As Adhemerval notes, this needs to go through POSIX or ISO C first
to standardize the '%r' and '%R' modifiers.

Working with the Austin Group is pretty easy actually, you need
to file a ticket with their system and discuss the change to the
standard:

Austin Group homepage:
http://www.opengroup.org/austin/

Austin Group bug tracker:
http://austingroupbugs.net/main_page.php

(b) Follow the contribution checklist.

After you have standardized the modifiers you go through the
contribution checklist here:
https://sourceware.org/glibc/wiki/Contribution%20checklist

(c) Needs tests.

You need tests for all of the characters you are adding, and
the output they might generate.

-- 
Cheers,
Carlos.

Re: [PATCH] Add Roman numerals in *printf

[Paul Eggert]

Matteo Croce wrote:
> ancient Roman numerals are often used to represent
> software version, protocol revision or even movie chapters.

That is the best April Fool joke I've seen in many a year!  Thanks and 
congratulations.  I had already composed an email that among other things 
corrected your Latin (it's "nulla", not "nihil"!) before I realized I'd been had.

Re: [PATCH] Add Roman numerals in *printf

[Martin Sebor]

> This patch adds the `%r' modifier in all the *printf functions,
> which can be used to represent a number in Roman numerals.

A bit late to the April 1 party, but a C++ Standard Library
implementation I worked on years ago actually has this feature.
It makes it possible to use the usual C++ iostream inserter and
extractor operators to format and parse not only Roman numerals
(that was done mostly just to give base 1 a meaning), but more
usefully numbers in any base between 1 and 36.  The implementation
still ships with a number of compilers, though I think only one
(Compaq/HP CC for Tru64) has the version with the Roman numerals.

Martin