type_ls: Declare type of a function

In kcf-jackson/declare: Optional type annotation

Description

Declare type of a function

Usage

type_ls(f, signature)

Arguments

f	A function; the function to which type-annotations are added.
signature	A named list of character vector. The type / classes. Union class is supported, e.g. list(arg_1 = c("numeric", "matrix")) is allowed.

Examples

## Not run: 
# Example 1
add_one <- function(x) { x + 1 }
add_one <- declare::type_ls(add_one, list(x = "numeric"))
add_one(10)          # Runs fine
add_one(nrow(1:10))  # Expect type error since nrow of a vector returns NULL.

# Example 2
cbind_rows <- function(r1, r2) { cbind(r1, r2) }
cbind_rows <- declare::type_ls(cbind_rows, list(r1 = "matrix", r2 = "matrix"))

X <- matrix(1:9, 3, 3)
Y <- matrix(1:3, ncol = 3)
cbind_rows(Y, Y)     # Runs fine
cbind_rows(X[1,], Y) # Expect type error since X[1,] is converted to vector implicitly.

# Example 3 - Partial specification
f <- function(x, y) { x[1:3, ] * y }
f <- declare::type_ls(f, list(y = "numeric"))  # 'x' is unspecified

x <- matrix(1:9, 3, 3)
x2 <- as.data.frame(x)
k <- 5
f(x, k)     # runs fine
f(x2, k)    # runs fine
f(x2, "A")  # type error

# Example 4 - Multiple labels
f <- function(x, y) { x[1:3, ] * y }
f <- declare::type_ls(f, list(x = c("matrix", "data.frame"), y = "numeric"))

x <- matrix(1:9, 3, 3)
x2 <- as.data.frame(x)
k <- 5
f(x, k)    # runs fine
f(x2, k)   # runs fine
f("A", k)  # type error

## End(Not run)

kcf-jackson/declare documentation built on May 29, 2019, 8:34 a.m.