Metaprogramming Example

Jun 2, 2021, updated Feb 28, 2022 #metaprogramming

# without metaprogramming
c_type <- function(action, type, x) {
    
    if (action == "is") {
        if (type == "numeric") {
            return(is.numeric(x))
        } else if (type == "character") {
            return(is.character(x))
        } else {
            return("type not found.")
        }
    } 
    
    if (action == "as") {
        if (type == "numeric") {
            return(as.numeric(x))
        } else if (type == "character") {
            return(as.character(x))
        } else {
            return("type not found.")
        }
    } 
    
    # catch
    return("action not found.")
    
}

# c_type("is", "numeric", 2)
# c_type("is", "numeric", "zzz")
# c_type("is", "character", "zzz")
# c_type("as", "character", "2")
# c_type("as", "numeric", "2e3")

# metaprogramming way
c_type_new <- function(action, type, x) {
    get(paste0(action, ".", type))(x)
}

# c_type_new("is", "numeric", 2)
# c_type_new("is", "numeric", "zzz")
# c_type_new("is", "character", "zzz")
# c_type_new("as", "character", "2")
# c_type_new("as", "numeric", "2e3")