On 19 August 2013 23:24, Roland Mainz <[email protected]> wrote: > On Mon, Aug 19, 2013 at 8:10 PM, David Korn <[email protected]> wrote: >> cc: [email protected] >> Subject: Re: Re: [ast-developers] float i; (( i.MAX, i.MIN, i.EPSILON )) >> constants? >> -------- >>> Erm... doesn't this just require a small modification of the >>> arithmetic engine (I don't know how to do the same for a plain >>> ${i.MAX}), e.g. do a type-based (technically we "only" have six types >>> - three integer and three float) lookup of the matching constant value >>> if an integer name is followed by a '.' ? >> >> First of all there are 9 types, 3 float, 3 integer, and 3 unsigned. >> >> Secondly, it is much simpler of i.MAX only appears in arithmetic >> expressions and cannot be used as ${i.MAX} because ${i.MAX} is >> more complex because it needs to work with ${i.MAX op string} >> and ${op i.MAX} as well. >> >> I am not even sure how to implement ${!i.M*} given the current >> architecture. >> >> Maybe I should restrict b.true to arithmetic expressions only. >> Programs that want ${i.MAX} can do $((i.MAX)). >> >> Anyway, I have enough bug reports to keep me busy for now. > > Attached (as "astksh20130814_math_constants001.diff.txt") is a > prototype patch which allows constants to be defined like this: > -- snip -- > $ ksh -o nounset -c 'compound .sh.mathconst=( float LDBL_M_PI=3.14 ) ; > float x=5.5 ; print $((x.M_PI)) ${x.M_PI}' > 3.14 3.14 > -- snip -- > > AFAIK we need the following constants (mostly derived from X/OPEN and > my own math code): > 1. min/max/etc. limits: > -- snip -- > # integer for $((i.MIN)) and $((i.MAX)) > SHRT_MIN > SHRT_MAX > USHRT_MAX > INT_MIN > INT_MAX > UINT_MAX > LONG_MAX > LONG_MAX > LONG_MIN > ULONG_MAX > ULONG_MAX > > # float for $((i.MANT_DIG , i.MIN_EXP , i.MIN_10_EXP, i.MAX_EXP , > i.MAX_10_EXP , i.MIN , i.MAX, i.EPSILON , i.DECIMAL_DIG) > FLT_MANT_DIG > DBL_MANT_DIG > LDBL_MANT_DIG > FLT_MIN_EXP > DBL_MIN_EXP > LDBL_MIN_EXP > FLT_MIN_10_EXP > DBL_MIN_10_EXP > LDBL_MIN_10_EXP > FLT_MAX_EXP > DBL_MAX_EXP > LDBL_MAX_EXP > FLT_MAX_10_EXP > DBL_MAX_10_EXP > LDBL_MAX_10_EXP > FLT_MAX > DBL_MAX > LDBL_MAX > FLT_EPSILON > DBL_EPSILON > LDBL_EPSILON > FLT_MIN > DBL_MIN > LDBL_MIN > FLT_DECIMAL_DIG > DBL_DECIMAL_DIG > LDBL_DECIMAL_DIG > -- snip -- > > 2. constants (need to be per-type to get round-offs correct): > -- snip -- > M_E 2.718281828459045235360287471352662498L /* e */ > M_LOG2E 1.442695040888963407359924681001892137L /* log_2 e */ > M_LOG10E 0.434294481903251827651128918916605082L /* log_10 e */ > M_LN2 0.693147180559945309417232121458176568L /* log_e 2 */ > M_LN10 2.302585092994045684017991454684364208L /* log_e 10 */ > M_PI 3.141592653589793238462643383279502884L /* pi */ > M_PI_2 1.570796326794896619231321691639751442L /* pi/2 */ > M_PI_4 0.785398163397448309615660845819875721L /* pi/4 */ > M_1_PI 0.318309886183790671537767526745028724L /* 1/pi */ > M_2_PI 0.636619772367581343075535053490057448L /* 2/pi */ > M_2_SQRTPI 1.128379167095512573896158903121545172L /* 2/sqrt(pi) */ > M_SQRT2 1.414213562373095048801688724209698079L /* sqrt(2) */ > M_SQRT1_2 0.707106781186547524400844362104849039L /* 1/sqrt(2) */ > -- snip -- > On a 2nd thought... maybe we should define these constants via C99 > hexfloat to make sure the last bits are OK...
Roland, thank you for the patch. I like it, except that it requires that constants have to be defined by hand, i.e. in each script again and again. Could you implement an internal table with these constants predefined, please? Tina -- Tina Harriott - Women in Mathematics Contact: [email protected] _______________________________________________ ast-developers mailing list [email protected] http://lists.research.att.com/mailman/listinfo/ast-developers
