[doc/mpfr.texi] m=1 is now valid in get_str

[src/get_str.c] allow m=1 for b=2^k
[tests/tget_str.c] added test for m=1 and b=2


git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@12432 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 4 insertions, 5 deletions

diff --git a/src/get_str.c b/src/get_str.c
index 442ac7166..c06d2d147 100644
--- a/src/get_str.c
+++ b/src/get_str.c
@@ -2325,15 +2325,12 @@ mpfr_get_str (char *s, mpfr_exp_t *e, int b, size_t m, mpfr_srcptr x,
       */
       m = 1 +
         mpfr_ceil_mul (IS_POW2(b) ? MPFR_PREC(x) - 1 : MPFR_PREC(x), b, 1);
-      if (m < 2)
-        m = 2;
     }
 
   MPFR_LOG_MSG (("m=%zu\n", m));
 
-  /* The code below for non-power-of-two bases works for m=1;
-     this is important for the internal use of mpfr_get_str. */
-  MPFR_ASSERTN (m >= 2 || (!IS_POW2(b) && m >= 1));
+  /* The code below works for m=1, both for power-of-two and non-power-of-two
+     bases; this is important for the internal use of mpfr_get_str. */
 
   /* x is a floating-point number */
 
@@ -2376,6 +2373,8 @@ mpfr_get_str (char *s, mpfr_exp_t *e, int b, size_t m, mpfr_srcptr x,
 
       /* the first digit will contain only r bits */
       prec = (m - 1) * pow2 + r; /* total number of bits */
+      /* if m=1 then 1 <= prec <= pow2, and since prec=1 is now valid in MPFR,
+         the power-of-two code also works for m=1 */
       n = MPFR_PREC2LIMBS (prec);
 
       MPFR_TMP_MARK (marker);