Closes #518. Edge cases fix for columns of type function.

R/data.table.R

@@ -275,6 +275,8 @@ data.table <-function(..., keep.rownames=FALSE, check.names=FALSE, key=NULL, str
         } else if (is.table(xi)) {
             x[[i]] = xi = as.data.table.table(xi, keep.rownames=keep.rownames)
             numcols[i] = length(xi)
+        } else if (is.function(xi)) {
+            x[[i]] = xi = list(xi)
         }
         nrows[i] <- NROW(xi)    # for a vector (including list() columns) returns the length
         if (numcols[i]>0L) {

README.md

@@ -228,6 +228,8 @@
 
   23. Fixed example in `?as.data.table.Rd`, [#1576](https://github.com/Rdatatable/data.table/issues/1576). Thanks @MichaelChirico.
 
+  24. Fixed an edge case and added tests for columns of type `function`, [#518](https://github.com/Rdatatable/data.table/issues/518).
+
 ### Changes in v1.9.6  (on CRAN 19 Sep 2015)
 
 #### NEW FEATURES

inst/tests/tests.Rraw

@@ -7923,6 +7923,17 @@ test(1635.1, ans1 <- fread(text, fill=TRUE), setDT(read.table(text=text, strings
 text = "a	b	c	d	e\n1	P	P;A;E;	Y	YW;	H().	1-3 pro\n2	Q9	a;a;a;a;	YB	YH;	M().	13 pn ba\n1	P3	P;	Y	Y;	R().	14 p\n53	P	P6;B;D;0;5;a;X;a;4R;	Y	Y;	H().	13 pe e\n1	P	P;O;O;a;a;a;	HLA-A	HLA-A;;	H().	HcIha,A-n\n102	P	P;O;P;P;P;P;P;P;a;a;a;a;a;a;a;a;a;a;	H-A	H-A;;	H().	HcIha,A"
 test(1635.2, fread(text, fill=TRUE), setnames(ans1[, 1:7, with=FALSE], c(letters[1:5], paste("V", 6:7, sep=""))))
 
+# testing function type in dt, #518
+dt = data.table(x=1, y=sum)
+test(1636.1, class(dt$y), "list")
+test(1636.2, any(grepl("1: 1 <function>", capture.output(print(dt)))), TRUE)
+dt = data.table(x=1:2, y=sum)
+test(1636.3, class(dt$y), "list")
+test(1636.4, any(grepl("2: 2 <function>", capture.output(print(dt)))), TRUE)
+dt = data.table(x=1:2, y=c(sum, min))
+test(1636.5, class(dt$y), "list")
+test(1636.6, any(grepl("2: 2 <function>", capture.output(print(dt)))), TRUE)
+
 ##########################
 
 # TODO: Tests involving GForce functions needs to be run with optimisation level 1 and 2, so that both functions are tested all the time.