| 182 |
|
} |
| 183 |
|
|
| 184 |
|
|
| 185 |
< |
getd(dp) /* get a positive double from stdin */ |
| 185 |
> |
getd(name, dp, help) /* get a positive double from stdin */ |
| 186 |
> |
char *name; |
| 187 |
|
double *dp; |
| 188 |
+ |
char *help; |
| 189 |
|
{ |
| 190 |
|
char buf[32]; |
| 191 |
< |
|
| 191 |
> |
again: |
| 192 |
> |
printf("%s [%g]: ", name, *dp); |
| 193 |
|
if (gets(buf) == NULL) |
| 194 |
|
return(0); |
| 195 |
+ |
if (buf[0] == '?') { |
| 196 |
+ |
puts(help); |
| 197 |
+ |
goto again; |
| 198 |
+ |
} |
| 199 |
|
if ((buf[0] < '0' || buf[0] > '9') && buf[0] != '.') |
| 200 |
|
return(0); |
| 201 |
|
*dp = atof(buf); |
| 205 |
|
|
| 206 |
|
getpolygon() /* get projected area for a polygon */ |
| 207 |
|
{ |
| 208 |
< |
printf("Polygon area? "); |
| 209 |
< |
if (!getd(&projarea)) |
| 210 |
< |
return(0); |
| 211 |
< |
projarea *= unit2meter*unit2meter; |
| 212 |
< |
projarea *= PI; |
| 208 |
> |
static double area = 1.0; |
| 209 |
> |
|
| 210 |
> |
getd("Polygon area", &area, |
| 211 |
> |
"Enter the total radiating area of the polygon."); |
| 212 |
> |
projarea = PI*unit2meter*unit2meter * area; |
| 213 |
|
return(1); |
| 214 |
|
} |
| 215 |
|
|
| 216 |
|
|
| 217 |
|
getsphere() /* get projected area for a sphere */ |
| 218 |
|
{ |
| 219 |
< |
double radius; |
| 219 |
> |
static double radius = 1.0; |
| 220 |
|
|
| 221 |
< |
printf("Sphere radius? "); |
| 222 |
< |
if (!getd(&radius)) |
| 223 |
< |
return(0); |
| 217 |
< |
radius *= unit2meter; |
| 218 |
< |
projarea = 4.*PI*PI*radius*radius; |
| 221 |
> |
getd("Sphere radius", &radius, |
| 222 |
> |
"Enter the distance from the sphere's center to its surface."); |
| 223 |
> |
projarea = 4.*PI*PI*unit2meter*unit2meter * radius*radius; |
| 224 |
|
return(1); |
| 225 |
|
} |
| 226 |
|
|
| 227 |
|
|
| 228 |
|
getcylinder() /* get projected area for a cylinder */ |
| 229 |
|
{ |
| 230 |
< |
double length, radius; |
| 230 |
> |
static double length = 1.0, radius = 0.1; |
| 231 |
|
|
| 232 |
< |
printf("Cylinder length? "); |
| 233 |
< |
if (!getd(&length)) |
| 234 |
< |
return(0); |
| 235 |
< |
length *= unit2meter; |
| 236 |
< |
printf("Cylinder radius? "); |
| 232 |
< |
if (!getd(&radius)) |
| 233 |
< |
return(0); |
| 234 |
< |
radius *= unit2meter; |
| 235 |
< |
projarea = PI*PI*2.*PI*radius*length; |
| 232 |
> |
getd("Cylinder length", &length, |
| 233 |
> |
"Enter the length of the cylinder."); |
| 234 |
> |
getd("Cylinder radius", &radius, |
| 235 |
> |
"Enter the distance from the cylinder's axis to its surface."); |
| 236 |
> |
projarea = PI*PI*2.*PI*unit2meter*unit2meter * radius*length; |
| 237 |
|
return(1); |
| 238 |
|
} |
| 239 |
|
|
| 240 |
|
|
| 241 |
|
getring() /* get projected area for a ring */ |
| 242 |
|
{ |
| 243 |
< |
double radius; |
| 243 |
> |
static double radius = 1.0; |
| 244 |
|
|
| 245 |
< |
printf("Disk radius? "); |
| 246 |
< |
if (!getd(&radius)) |
| 247 |
< |
return(0); |
| 248 |
< |
radius *= unit2meter; |
| 248 |
< |
projarea = PI*PI*radius*radius; |
| 245 |
> |
getd("Disk radius", &radius, |
| 246 |
> |
"Enter the distance from the ring's center to its outer edge.\n\ |
| 247 |
> |
The inner radius must be zero."); |
| 248 |
> |
projarea = PI*PI*unit2meter*unit2meter * radius*radius; |
| 249 |
|
return(1); |
| 250 |
|
} |
