From e04883d448df6e622535020449903e2f2a0f32c9 Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang-solutions.com>
Date: Tue, 26 Jul 2011 17:11:41 +0200
Subject: Update integer and floating point number comparisons

For floating point values which are greater than 9007199254740990.0 or
smaller than -9007199254740990.0, the floating point numbers are now
converted to integers during comparison with an integer. This makes
number comparisons transitive for large floating point numbers.
---
 erts/emulator/beam/big.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

(limited to 'erts/emulator/beam/big.c')

diff --git a/erts/emulator/beam/big.c b/erts/emulator/beam/big.c
index d18de9ae5d..51e5d2d305 100644
--- a/erts/emulator/beam/big.c
+++ b/erts/emulator/beam/big.c
@@ -1584,6 +1584,63 @@ big_to_double(Wterm x, double* resp)
     return 0;
 }
 
+Eterm
+double_to_big(double x, Eterm *heap)
+{
+    int is_negative;
+    int ds;
+    ErtsDigit* xp;
+    Eterm tmp_res;
+    int i;
+    size_t sz;
+    Eterm* hp;
+    double dbase;
+
+    if ((x < (double) (MAX_SMALL + 1)) && (x > (double) (MIN_SMALL - 1))) {
+	Sint xi = x;
+	return make_small(xi);
+    }
+
+    if (x >= 0) {
+	is_negative = 0;
+    } else {
+	is_negative = 1;
+	x = -x;
+    }
+
+    /* Unscale & (calculate exponent) */
+    ds = 0;
+    dbase = ((double) (D_MASK) + 1);
+    while (x >= 1.0) {
+	x /= dbase; /* "shift" right */
+	ds++;
+    }
+    sz = BIG_NEED_SIZE(ds); /* number of words including arity */
+
+    hp = heap;
+    tmp_res = make_big(hp);
+    xp = (ErtsDigit*) (hp + 1);
+
+    for (i = ds - 1; i >= 0; i--) {
+	ErtsDigit d;
+
+	x *= dbase; /* "shift" left */
+	d = x; /* trunc */
+	xp[i] = d; /* store digit */
+	x -= d; /* remove integer part */
+    }
+    while ((ds & (BIG_DIGITS_PER_WORD - 1)) != 0) {
+	xp[ds++] = 0;
+    }
+
+    if (is_negative) {
+	*hp = make_neg_bignum_header(sz-1);
+    } else {
+	*hp = make_pos_bignum_header(sz-1);
+    }
+    return tmp_res;
+}
+
 
 /*
  ** Estimate the number of decimal digits (include sign)
-- 
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