Precision lost with double numbers #33
Description
When testing nullc with the tests from https://github.com/ArashPartow/exprtk there is a big difference in the total of equal expressions compared to C/C++ or other programming languages:
import std.io;
import std.math;
int total_count = 0;
int total_eq = 0;
void equal(double a, double b) {
++total_count;
if(a == b) {
++total_eq;
}
//else { io.out << a << "<>" << b << io.endl;}
else { io.out << total_count << "\t";Print(a, 16); io.out << "<>"; Print(b, 16); io.out << io.endl;}
}
double x, y, z, w;
x=11.12345678910737373;
y=22.12345678910737373;
z=33.12345678910737373;
w=44.12345678910737373;
//...
equal((-10.123456789107372000000000000000),(3-(2+abs(x))));
equal((-10.123456789107372000000000000000),(3-(abs(x)+2)));
io.out << "-10.123456789107372" << " == " << -10.123456789107372000000000000000 << " == "; Print(-10.123456789107372000000000000000, 16); io.out << io.endl;
io.out << total_count << "\t" << total_eq << io.endl;
return 0;
Output before :
-10.123456789107372 == -10.123456790947 == -10.1234567909470208
7366 417
Output after:
-10.123456789107372 == -10.123456789107 == -10.1234567891073723
7366 6923
Patch to get a better double precision and also accept numbers like .23, -.34, ...:
--------------------------- NULLC/ExpressionTree.cpp ---------------------------
index 40da9356..f6fd3dbc 100644
@@ -269,7 +269,7 @@ namespace
if(*str == '.')
{
- double power = 0.1f;
+ double power = 0.1;
str++;
while((digit = *str - '0') < 10)
@@ -280,7 +280,7 @@ namespace
}
}
- if(*str == 'e')
+ if(*str == 'e' || *str == 'E')
{
str++;
@@ -3792,7 +3792,7 @@ ExprBase* AnalyzeNumber(ExpressionContext &ctx, SynNumber *syntax)
for(unsigned i = 0; i < value.length(); i++)
{
- if(value.begin[i] == '.' || value.begin[i] == 'e')
+ if(value.begin[i] == '.' || value.begin[i] == 'e' || value.begin[i] == 'E')
isFP = true;
}
------------------------------- NULLC/Lexer.cpp -------------------------------
index 6ce9c8de..4fcd7649 100644
@@ -132,7 +132,8 @@ void Lexer::Lexify(const char* code)
}
break;
case '.':
- lType = lex_point;
+ if(isDigit(code[1])) goto do_lex_number;
+ else lType = lex_point;
break;
case ',':
lType = lex_comma;
@@ -392,6 +393,7 @@ void Lexer::Lexify(const char* code)
default:
if(isDigit(*code))
{
+do_lex_number:
lType = lex_number;
const char *pos = code;
@@ -408,7 +410,7 @@ void Lexer::Lexify(const char* code)
pos++;
while(isDigit(*pos))
pos++;
- if(*pos == 'e')
+ if(*pos == 'e' || *pos == 'E')
{
pos++;
if(*pos == '-')
Full test source
exprtk_functional_test.nc.zip