icecream is designed to make print debugging easier. It allows you to print out an expression, its value and (optionally) which function and file the call originated in.
This is an R port of gruns/icecream. All credit for the idea belongs to Ansgar Grunseid.
Install from CRAN with:
install.packages("icecream")
Or you can install the development version from GitHub with:
devtools::install_github("lewinfox/icecream")
The ic()
function prints its argument and its value. It also returns
the value of the evaluated argument, meaning that it is effectively
transparent in code - just wrap an expression in ic()
to get debugging
output.
library(icecream)
is_negative <- function(x) x < 0
ic(is_negative(1))
#> ℹ ic| `is_negative(1)`: logi FALSE
ic(is_negative(-1))
#> ℹ ic| `is_negative(-1)`: logi TRUE
You’re more likely to want to do this within a function:
some_function <- function(x) {
intermediate_value <- x * 10
answer <- ic(intermediate_value / 2)
return(answer)
}
some_function(1)
#> ℹ ic| `intermediate_value / 2`: num 5
#> [1] 5
some_function(10)
#> ℹ ic| `intermediate_value / 2`: num 50
#> [1] 50
More complex inputs like lists and data frames are summarised to avoid cluttering the terminal.
df <- ic(iris)
#> ℹ ic| `iris`: data.frame [150 x 5]: $'Sepal.Length': dbl [150], ...
my_list <- ic(list(a = 1, b = 3, c = 1:100))
#> ℹ ic| `list(a = 1, b = 3, c = 1:100)`: list [3]: $'a': dbl [1], $'b': dbl [1], $'c': int [100]
Calling ic()
with no arguments causes it to print out the file, line
and parent function it was called from.
In this example we have a file demo.R
that contains two functions.
We’ve inserted ic()
calls at strategic points so we can track what’s
being executed.
# demo.R
f1 <- function(x) {
ic()
if (x > 0) {
f2()
}
}
f2 <- function() {
ic()
}
f3 <- function(x) {
ic(x)
}
source("demo.R")
f1(-1)
#> ℹ ic| `global::f1()` in demo.R:3:2
f1(1)
#> ℹ ic| `global::f1()` in demo.R:3:2
#> ℹ ic| `global::f2()` in demo.R:10:2
In the case of functions that haven’t been source()
d or loaded from a
package there is no source code to refer to. In these cases the
function’s environment will be displayed.
orphan_func <- function() {
ic()
TRUE
}
orphan_func()
#> ℹ ic| `global::orphan_func()` in <env: global>
#> [1] TRUE
e <- new.env()
attr(e, "name") <- "icecream_van"
environment(orphan_func) <- e
orphan_func()
#> ℹ ic| `orphan_func()` in <env: icecream_van>
#> [1] TRUE
The ic_enable()
and ic_disable()
functions enable or disable the
ic()
function. If disabled, ic()
will return the result of
evaluating its input but will not print anything.
ic_enable() # This is TRUE by default
ic(mean(1:100))
#> ℹ ic| `mean(1:100)`: num 50.5
ic_disable()
ic(mean(1:100))
#> [1] 50.5
Convenience functions with_ic_enable()
and with_ic_disable()
are
also provided.
ic_enable()
with_ic_disable(ic(mean(1:100)))
#> [1] 50.5
ic_disable()
with_ic_enable(ic(mean(1:100)))
#> ℹ ic| `mean(1:100)`: num 50.5
The following options can be used to control behaviour:
icecream.enabled
Boolean. If FALSE
, calls to ic(foo)
simply evaluate and return
foo
. No output is printed. This option can be set directly or with the
ic_enable()
and ic_disable()
functions.
icecream.prefix
This is printed at the beginning of every line. Defaults to "ic|"
.
ic(mean(1:5))
#> ℹ ic| `mean(1:5)`: num 3
options(icecream.prefix = "DEBUG:")
ic(mean(1:5))
#> ℹ DEBUG: `mean(1:5)`: num 3
options(icecream.prefix = "\U1F366")
ic(mean(1:5))
#> ℹ 🍦 `mean(1:5)`: num 3
icecream.always.include.context
Boolean. If TRUE
, when calling ic(foo)
the source file and line will
be printed along with the expression and value. If no srcref()
is
available the function’s environment will be displayed instead. This can
be useful for more complicated debugging but produces a lot of output so
is disabled by default.
f3(1)
#> ℹ ic| `x`: num 1
options(icecream.always.include.context = TRUE)
f3(1)
#> ℹ ic| `global::f3()` in demo.R:14:2 | `x`: num 1
When ic()
is called with no arguments, the context is always printed
because showing the location of the call is the only reason to call
ic()
on its own.
icecream.peeking.function
and icecream.max.lines
These two options control how the result of evaluation of an expression
is printed. icecream.peeking.function
indicates the function that
summarizes the object. Default value is ic_autopeek
, which works like
utils::str
for most of the time, but gives more informative output for
lists
, data.frames
and their subclasses in a more compact way.
icecream.max.lines
determines maximum number of lines that the peek of
an object occupies; defaults to 1.
For more complex data you may want to use e.g. head
function and 5
lines.
data(iris)
ic(iris) # we would like to see header of the data
#> ℹ ic| `iris`: data.frame [150 x 5]: $'Sepal.Length': dbl [150], ...
options(icecream.peeking.function = head,
icecream.max.lines = 5)
ic(iris)
#> ℹ ic| `iris`:
#> Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#> 1 5.1 3.5 1.4 0.2 setosa
#> 2 4.9 3.0 1.4 0.2 setosa
#> 3 4.7 3.2 1.3 0.2 setosa
#> 4 4.6 3.1 1.5 0.2 setosa
Note that if icecream.max.lines
is greater than 1 and summary of an
object is longer than 1, the alert occupies one line more due to the
header.
icecream.output.function
, icecream.arg.to.string.function
Not implemented yet. See the configuration section of the original project docs for details of what they will do.
ic.format()
(see
here).ic.output.function
. At the moment it uses
cli::cli_alert_info()
ic.arg.to.string.function
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