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("Enter area of polygon: "); |
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("Enter 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("Enter cylinder length: "); |
233 |
< |
if (!getd(&length)) |
234 |
< |
return(0); |
235 |
< |
length *= unit2meter; |
236 |
< |
printf("Enter 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("Enter 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 |
|
} |