源程序:
//==============================================================================
==============
//
//==============================================================================
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void DispF(float f) reentrant //用科学记数法显示浮点数,在float全范围内精确显
示,超出范围给出提示。
{ //+-1.175494E-38到+-3.402823E+38
float tf,b;
unsigned long w,tw;
char i,j;
if(f<0){
PrintChar(’-’);
f=-1.0*f;
}
if(f<1.175494E-38){
yyprintf("?.??????");//太小了,超出了最小范围。
return;
}
if(f>1E35){ //f>10^35
tf=f/1E35;
b=1000.0;
for(i=0,j=38;i<4;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f/(1E29*b); //1E35*b/1E6
PrintW(w,j);
}
else if(f>1E28){ //10^28 tf=f/1E28;
b=1E7;
for(i=0,j=35;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f/(1E22*b); //1E28*b/1E6
PrintW(w,j);
}
else if(f>1E21){ //10^21 tf=f/1E21;
b=1E7;
for(i=0,j=28;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f/(1E15*b); //1E21*b/1E6
PrintW(w,j);
}
else if(f>1E14){ //10^14 tf=f/1E14;
b=1E7;
for(i=0,j=21;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f/(1E8*b); //1E14*b/1E6
PrintW(w,j);
}
else if(f>1E7){ //10^7 tf=f/1E7;
b=1E7;
for(i=0,j=14;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f/(10.0*b); //1E28*b/1E6
PrintW(w,j);
}
else if(f>1){ //1 tf=f;
b=1E7;
for(i=0,j=7;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f/(1E-6*b); //1E0*b/1E6
PrintW(w,j);
}
else if(f>1E-7){ //10^-7 tf=f*1E7;
b=1E7;
for(i=0,j=0;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f*(1E13/b); //(1E7/b)*1E6
PrintW(w,j);
}
else if(f>1E-14){ //10^-14 tf=f*1E14;
b=1E7;
for(i=0,j=-7;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f*(1E20/b); //(1E14/b)*1E6
PrintW(w,j);
}
else if(f>1E-21){ //10^-21 tf=f*1E21;
b=1E7;
for(i=0,j=-14;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f*(1E27/b); //(1E21/b)*1E6
PrintW(w,j);
}
else if(f>1E-28){ //10^-28 tf=f*1E28;
b=1E7;
for(i=0,j=-21;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f*(1E34/b); //(1E28/b)*1E6
PrintW(w,j);
}
else if(f>1E-35){ //10^-35 tf=f*1E35;
b=1E7;
for(i=0,j=-28;i<8;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f*(1E35/b)*1E6; //(1E35/b)*1E6
PrintW(w,j);
}
else{ //f<=10^-35
tf=f*1E38;
b=1000.0;
for(i=0,j=-35;i<4;i++,j--)
if(tf/b<1) b=b/10.0;
else break;
w=f*(1E38/b)*1E6; //(1E38/b)*1E6
PrintW(w,j);
}
}
void PrintW(unsigned long w,char j) reentrant //科学记数法,显示十进制尾数和阶
码。
{
char i;
unsigned long tw,b;
//if(j<-38){yyprintf("?.??????");return;}//太小了,超出最小表数范围。
//if(j>38){yyprintf("*.******");return;}此算法不会出现j>38的情况。
tw=w/1000000;
PrintChar(tw+’0’);PrintChar(’.’);
w=w-tw*1000000;
b=100000;
for(i=0;i<6;i++){
tw=w/b;
PrintChar(tw+’0’);
w=w-tw*b;
b=b/10;
}
yyprintf("E%d",(int)j);
} |