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Re: [bug-grep] Re: length of dec. representation of a number
From: |
Stepan Kasal |
Subject: |
Re: [bug-grep] Re: length of dec. representation of a number |
Date: |
Thu, 10 Mar 2005 10:09:54 +0100 |
User-agent: |
Mutt/1.4.1i |
Hello Paul,
thank you for the improved version. Let me make a summary of comments
submitted by Paul Jarc, and add one idea of mine.
Text which is not modified is left with the "> " tags.
----------
/* The extra casts in the following macros are either needed because of
integer promotion, or to work around compiler bugs, e.g., in
Cray C 5.0.3.0. */
> /* True if the arithmetic type T is an integer type. bool counts as
> an integer. */
> #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)
>
> /* True if negative values of the signed integer type T use twos
> complement, ones complement, or signed magnitude representation,
> respectively. Much GNU code assumes twos complement, but some
> people like to be portable to all possible C hosts. */
> #define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1)
> #define TYPE_ONES_COMPLEMENT(t) ((t) ~ (t) 0 == 0)
> #define TYPE_SIGNED_MAGNITUDE(t) ((t) ~ (t) 0 < (t) -1)
/* True if the arithmetic type T is signed. */
#define TYPE_SIGNED(t) ((t) 1 > (t) -1)
> /* The maximum and minimum values for the integer type T. These
> macros have undefined behavior if T is signed and has padding bits.
> If this is a problem for you, please let us know how to fix it for
> your host. */
> #define TYPE_MINIMUM(t) \
> ((t) (! TYPE_SIGNED (t) \
> ? (t) 0 \
> : TYPE_SIGNED_MAGNITUDE (t) \
> ? ~ (t) 0 \
> : ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1)))
/* Note that we cannot use (1 << ...) on the last line, because << can
act as sign-preserving shift. (In theory, << is undefined as soon as
the leftmost bit of the left operand is set, no matter whether the
type is signed or not, but in practice this code works.) */
> #define TYPE_MAXIMUM(t) \
> ((t) (! TYPE_SIGNED (t) \
> ? (t) -1 \
> : ~ (~ (t) 0 << (sizeof (t) * CHAR_BIT - 1))))
For unsigned types on signed magnitude hosts, ((t) -1) is wrong.
#define TYPE_MAXIMUM(t) \
((t) (! TYPE_SIGNED (t) \
? ~ (t) 0 \
: ~ (~ (t) 0 << (sizeof (t) * CHAR_BIT - 1))))
> /* Bound on length of the string representing an integer value or type T.
> Subtract 1 for the sign bit if t is signed; log10 (2.0) < 146/485;
> add 1 for integer division truncation; add 1 more for a minus sign
> if needed. */
#define INT_STRLEN_BOUND(t) \
((sizeof (t) * CHAR_BIT - TYPE_SIGNED (t)) * 146 / 485 + 1 \
+ TYPE_SIGNED (t))
> /* Bound on buffer size needed to represent an integer value or type T,
> including the terminating null. */
> #define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1)
Paul, will you accept these changes?
Stepan
- Re: [bug-grep] length of dec. representation of a number, (continued)
- Re: [bug-grep] length of dec. representation of a number, Paul Jarc, 2005/03/08
- Re: [bug-grep] length of dec. representation of a number, Jim Meyering, 2005/03/08
- Re: [bug-gnulib] Re: [bug-grep] length of dec. representation of a number, Stepan Kasal, 2005/03/09
- Re: [bug-gnulib] Re: [bug-grep] length of dec. representation of a number, Paul Jarc, 2005/03/09
- [bug-grep] Re: length of dec. representation of a number, Paul Eggert, 2005/03/09
- [bug-grep] Re: length of dec. representation of a number, Paul Jarc, 2005/03/10
- Re: [bug-grep] Re: length of dec. representation of a number, Jim Meyering, 2005/03/10
- Re: length of dec. representation of a number [bug-grep] [bug-gnulib], Stepan Kasal, 2005/03/10
- Re: [bug-grep] Re: length of dec. representation of a number, Paul Jarc, 2005/03/10
- Re: [bug-grep] Re: length of dec. representation of a number, Jim Meyering, 2005/03/10
- Re: [bug-grep] Re: length of dec. representation of a number,
Stepan Kasal <=
- Re: [bug-grep] Re: length of dec. representation of a number, Paul Jarc, 2005/03/10
- Re: [bug-grep] Re: length of dec. representation of a number, Paul Eggert, 2005/03/10