You Should Rarely Need `eval(parse())` | /en/2023/02/eval-parse/

giscus 2023-09-07 14:04:45

You Should Rarely Need `eval(parse())`

Many programming languages have a function to evaluate a string as code or an expression, e.g., eval() in R. Once you learn it, it becomes tempting to abuse it. Instead of writing code naturally and …

https://yihui.org/en/2023/02/eval-parse/

1 Comment

fncokg 2023-09-07 14:04:46

I found that in function ppclust::fcm, there are many codes like this:

compd <- parse(text = paste0(".compdist(x[i,], v[j,], dmetric='", dmetric, "', p=", pw, ")"))
# some other codes
for(j in 1:k)
    for(i in 1:n)
        d[i,j] <- eval(compd)

I'm surprised and I wonder why not simply replace those codes with this:

for(j in 1:k)
    for(i in 1:n)
        d[i,j] <- .compdist(x[i,],v[j,],dmetric=dmetric,p=pw)

yihui 2023-09-07 14:16:47

Indeed there are many eval() calls in this package: https://github.com/search?q=repo%3Acran%2Fppclust+eval%28&type=code I think you are right that these eval(parse()) calls are unnecessary. You may contact its authors and see if we missed anything.

You Should Rarely Need `eval(parse())` | /en/2023/02/eval-parse/

You Should Rarely Need eval(parse())

1 Comment

You Should Rarely Need `eval(parse())`