+ case OP_ADDNAN:
+ stackunderflow(1);
+ if (isnan(rpnstack->s[stptr - 1])) {
+ rpnstack->s[stptr - 1] = rpnstack->s[stptr];
+ } else if (isnan(rpnstack->s[stptr])) {
+ /* NOOP */
+ /* rpnstack->s[stptr - 1] = rpnstack->s[stptr - 1]; */
+ } else {
+ rpnstack->s[stptr - 1] = rpnstack->s[stptr - 1]
+ + rpnstack->s[stptr];
+ }
+
+ stptr--;
+ break;