e2<-function(a) integrate(function(x) x,lower=0,upper=a)$integral
integrate(e2,lower=0, upper=0.5)$integral

报错
1: Warning messages:
Condition has 15 elements: only the first used in: e1 && e2
2: Condition has 15 elements: only the first used in: if(lower == upper) { ....
Problem in h * intervals: length of longer operand (15) should be a multiple of length of shorter (7)