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(scm_ash): Revise docstring as per recent update to manual.

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Kevin Ryde 2003-10-19 00:27:00 +00:00
parent 9a848baf55
commit 32f19569bc
1 changed files with 13 additions and 9 deletions
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22
libguile/numbers.c
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@ -1367,20 +1367,24 @@ SCM_DEFINE (scm_integer_expt, "integer-expt", 2, 0, 0,
SCM_DEFINE (scm_ash, "ash", 2, 0, 0,
(SCM n, SCM cnt),
"The function ash performs an arithmetic shift left by @var{cnt}\n"
"bits (or shift right, if @var{cnt} is negative). 'Arithmetic'\n"
"means, that the function does not guarantee to keep the bit\n"
"structure of @var{n}, but rather guarantees that the result\n"
"will always be rounded towards minus infinity. Therefore, the\n"
"results of ash and a corresponding bitwise shift will differ if\n"
"@var{n} is negative.\n"
"Return @var{n} shifted left by @var{cnt} bits, or shifted right\n"
"if @var{cnt} is negative. This is an ``arithmetic'' shift.\n"
"\n"
"Formally, the function returns an integer equivalent to\n"
"@code{(inexact->exact (floor (* @var{n} (expt 2 @var{cnt}))))}.\n"
"This is effectively a multiplication by 2^@var{cnt}}, and when\n"
"@var{cnt} is negative it's a division, rounded towards negative\n"
"infinity. (Note that this is not the same rounding as\n"
"@code{quotient} does.)\n"
"\n"
"With @var{n} viewed as an infinite precision twos complement,\n"
"@code{ash} means a left shift introducing zero bits, or a right\n"
"shift dropping bits.\n"
"\n"
"@lisp\n"
"(number->string (ash #b1 3) 2) @result{} \"1000\"\n"
"(number->string (ash #b1010 -1) 2) @result{} \"101\"\n"
"\n"
";; -23 is bits ...11101001, -6 is bits ...111010\n"
"(ash -23 -2) @result{} -6\n"
"@end lisp")
#define FUNC_NAME s_scm_ash
{