Changeset 7470:77fc98e0bcb8

Timestamp:

12/01/07 13:15:38 (5 years ago)

Author:

Mike Hansen <mhansen@…>

Branch:

default

Message:

Fixed #962.

Location:

sage

Files:

• misc/functional.py (modified) (1 diff)
• rings/real_mpfr.pyx (modified) (5 diffs)

sage/misc/functional.py

@@ -724 +724 @@
             prec = 53
         else:
-            prec = int(digits * 3.4) + 2
+            prec = int((digits+1) * 3.32192) + 1
     try:
         return x.numerical_approx(prec)

sage/rings/real_mpfr.pyx

@@ -938 +938 @@
             no_sci = not (<RealField>self._parent).sci_not
 
-        if no_sci is True and (-exponent > digits or exponent > 2*digits):
+        if no_sci is True and ( abs(exponent-1) >=6 ):
             no_sci = False
 
@@ -947 +947 @@
 
         lpad = ''
+
         if exponent <= 0:
             n = len(t)
@@ -952 +953 @@
         else:
             n = exponent
+            
         if t[0] == '-':
             lpad = '-' + lpad
@@ -957 +959 @@
         z = lpad + str(t[:n])
         w = t[n:]
-        if len(w) > 0:
+
+        if len(w) > 0 and '.' not in z:         
             z = z + ".%s"%w
         elif exponent > 0:
-            z = z + '0'*(n-len(t))
+            z = z + '0'*(n-len(t))    
         if '.' not in z:
-            z = z + '.'
+            z = z + "."
+            
         return z
 
@@ -2981 +2985 @@
     if not isinstance(s, str):
         s = str(s)
-    if base == 10:
-        bits = int(3.32192*len(s))
+        
+    if 'e' in s or 'E' in s:
+        #Figure out the exponent
+        index = max( s.find('e'), s.find('E') )
+        exponent = int(s[index+1:])
+        rest = s[:index]
+
+        #Find the first nonzero entry in rest
+        sigfigs = 0
+        for i in range(len(rest)):
+            if rest[i] != '.' and rest[i] != '0':
+                sigfigs = len(rest) - i
+                break
+        
+        if base == 10:
+            bits = int(3.32192*sigfigs)+1
+        else:
+            bits = int(math.log(base,2)*sigfigs)+1
     else:
-        bits = int(math.log(base,2)*len(s))
+        #Find the first nonzero entry in s
+        sigfigs = 0
+        for i in range(len(s)):
+            if s[i] != '.' and s[i] != '0':
+                sigfigs = len(s) - i
+                break
+            
+        if base == 10:
+            bits = int(3.32192*sigfigs)+1
+        else:
+            bits = int(math.log(base,2)*sigfigs)+1
+
     R = RealField(prec=max(bits+pad, min_prec), rnd=rnd)
     return RealNumber(R, s, base)