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); |
207 |
|
{ |
208 |
|
static double area = 1.0; |
209 |
|
|
210 |
< |
printf("Polygon area [%g]: ", area); |
211 |
< |
getd(&area); |
210 |
> |
getd("Polygon area", &area, |
211 |
> |
"Enter the total radiating area of the polygon."); |
212 |
|
projarea = PI*unit2meter*unit2meter * area; |
213 |
|
return(1); |
214 |
|
} |
218 |
|
{ |
219 |
|
static double radius = 1.0; |
220 |
|
|
221 |
< |
printf("Sphere radius [%g]: ", radius); |
222 |
< |
getd(&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 |
|
} |
229 |
|
{ |
230 |
|
static double length = 1.0, radius = 0.1; |
231 |
|
|
232 |
< |
printf("Cylinder length [%g]: ", length); |
233 |
< |
getd(&length); |
234 |
< |
printf("Cylinder radius [%g]: ", radius); |
235 |
< |
getd(&radius); |
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 |
|
} |
242 |
|
{ |
243 |
|
static double radius = 1.0; |
244 |
|
|
245 |
< |
printf("Disk radius [%g]: ", radius); |
246 |
< |
getd(&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 |
|
} |