A problem in branch

[wukefe]

1. expr <- quote(lapply(data, function(x){if(x>5)x=x+1;x})) #get an expression
2. vexpr <- va_compile(expr) #vectorize the expression

The value of expr:

> expr
lapply(data, function(x) {
    if (x > 5) 
        x = x + 1
    x
})

The value of vexpr:

> vexpr
va_vec2list((function (x) 
{
    ifelse(x > 5, x = x + 1, NULL)
    x
})({
    if (!(exists(".va.data", inherits = FALSE) && (is.null(.vasrc.data) || 
        identical(.vasrc.data, data)))) {
        .va.data <- va_list2vec(data)
        .vasrc.data <- data
    }
    .va.data
}))

An error occurs as follows.

> eval(vexpr)
Error in ifelse(x > 5, x = x + 1, NULL) : replacement has length zero
In addition: Warning message:
In rep(no, length.out = length(ans)) :
  'x' is NULL so the result will be NULL

The problem should be in ifelse statement.

> w = 1:10
> ifelse(w>5,w=w+1,NULL)
Error in ifelse(w > 5, w = w + 1, NULL) : unused argument (w = w + 1)
> w=ifelse(w>5,w+1,w)
> w
 [1]  1  2  3  4  5  7  8  9 10 11

[wanghc78]

Yes, I confirm this bug. The problem is from ifelse. It cannot handle NULL value correctly. In this example, the if the if condition is false, the whole expression should return NULL. In the vectorized situation, the lane should return NULL, too.

The problem is R does not support mix NULL with a valid value. like

nullvec <- c(NULL, NULL, NULL) 
print(nullvec) #show one NULL
mixnull <- c(NULL, 10, NULL)
print(mixnull) #show only one 10

So we cannot input NULL into the ifelse call, but should insert something else. We can insert w in your simple case. For more general case, I have no clear idea now.