From 8df5087b9d34f8412ef9968ecccfe6674241883f Mon Sep 17 00:00:00 2001
From: hyung-hwan <hyunghwan.chung@gmail.com>
Date: Fri, 30 Mar 2018 18:11:11 +0000
Subject: [PATCH] enhanced the multiplication function to truncate the
 resulting fixed-point decimal to the equal precision to the operands

---
 lib/number.c | 41 +++++++++++++++++++++++++++++++++--------
 lib/read.c   |  9 ++++++---
 2 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/lib/number.c b/lib/number.c
index 83314b0..99b87a3 100644
--- a/lib/number.c
+++ b/lib/number.c
@@ -96,6 +96,26 @@ static hcl_ooi_t equalize_scale (hcl_t* hcl, hcl_oop_t* x, hcl_oop_t* y)
 	return xs;
 }
 
+static hcl_oop_t truncate (hcl_t* hcl, hcl_oop_t iv, hcl_ooi_t cs, hcl_ooi_t ns)
+{
+	/* this function truncates an existing fixed-point decimal.
+	 * it doesn't create a new object */
+
+	if (cs > ns)
+	{
+		do
+		{
+			/* TODO: optimizatino... less divisions */
+			iv = hcl_divints(hcl, iv, HCL_SMOOI_TO_OOP(10), 0, HCL_NULL);
+			if (!iv) return HCL_NULL;
+			cs--;
+		}
+		while (cs > ns);
+	}
+
+	return iv;
+}
+
 hcl_oop_t hcl_addnums (hcl_t* hcl, hcl_oop_t x, hcl_oop_t y)
 {
 	if (!HCL_IS_FPDEC(hcl, x) && !HCL_IS_FPDEC(hcl, y))
@@ -156,7 +176,7 @@ hcl_oop_t hcl_subnums (hcl_t* hcl, hcl_oop_t x, hcl_oop_t y)
 
 hcl_oop_t hcl_mulnums (hcl_t* hcl, hcl_oop_t x, hcl_oop_t y)
 {
-	hcl_ooi_t xs, ys, scale;
+	hcl_ooi_t xs, ys, cs, ns;
 	hcl_oop_t nv;
 	hcl_oop_t xv, yv;
 
@@ -189,16 +209,21 @@ hcl_oop_t hcl_mulnums (hcl_t* hcl, hcl_oop_t x, hcl_oop_t y)
 	nv = hcl_mulints(hcl, xv, yv);
 	if (!nv) return HCL_NULL;
 
-	scale = xs + ys;
-	if (scale > HCL_SMOOI_MAX)
-	{
-		/* TODO: limit scale */
-	}
+	cs = xs + ys; 
+	if (cs <= 0) return nv; /* the result must be an integer */
 
-	return hcl_makefpdec(hcl, nv, scale);
+	ns = (xs > ys)? xs: ys;
+
+	/* cs may be larger than HCL_SMOOI_MAX. but ns is guaranteed to be
+	 * equal to or less than HCL_SMOOI_MAX */
+	HCL_ASSERT (hcl, ns > 0 && ns <= HCL_SMOOI_MAX);
+
+	nv = truncate(hcl, nv, cs, ns);
+	if (!nv) return HCL_NULL;
+
+	return hcl_makefpdec(hcl, nv, ns);
 }
 
-
 hcl_oop_t hcl_divnums (hcl_t* hcl, hcl_oop_t x, hcl_oop_t y)
 {
 	hcl_ooi_t xs, ys, i;
diff --git a/lib/read.c b/lib/read.c
index ecc0046..7efa3f5 100644
--- a/lib/read.c
+++ b/lib/read.c
@@ -260,12 +260,14 @@ static hcl_oop_t string_to_fpdec (hcl_t* hcl, hcl_oocs_t* str, const hcl_ioloc_t
 				return HCL_NULL;
 			}
 
-			if (scale > 0) HCL_MEMMOVE (&str->ptr[pos], &str->ptr[pos + 1], scale * HCL_SIZEOF(str->ptr[0]));
+			HCL_ASSERT (hcl, scale > 0);
+			/*if (scale > 0)*/ HCL_MEMMOVE (&str->ptr[pos], &str->ptr[pos + 1], scale * HCL_SIZEOF(str->ptr[0]));
+			break;
 		}
 	}
 
 	v = hcl_strtoint(hcl, str->ptr, str->len - 1, 10);
-	if (scale > 0) HCL_MEMMOVE (&str->ptr[pos + 1], &str->ptr[pos], scale * HCL_SIZEOF(str->ptr[0]));
+	/*if (scale > 0)*/ HCL_MEMMOVE (&str->ptr[pos + 1], &str->ptr[pos], scale * HCL_SIZEOF(str->ptr[0]));
 	if (!v) return HCL_NULL;
 
 	return hcl_makefpdec (hcl, v, scale);
@@ -1156,7 +1158,8 @@ retry:
 					GET_CHAR_TO (hcl, c);
 					if (!is_digitchar(c))
 					{
-						hcl_setsynerrbfmt (hcl, HCL_SYNERR_NUMLIT, TOKEN_LOC(hcl), TOKEN_NAME(hcl), "invalid numeric literal with no digit after fixed-point");
+						/* the first character after the decimal point is not a decimal digit */
+						hcl_setsynerrbfmt (hcl, HCL_SYNERR_NUMLIT, TOKEN_LOC(hcl), TOKEN_NAME(hcl), "invalid numeric literal with no digit after decimal point");
 						return -1;
 					}
 				}