R devel - Sep 2022 - Passing a call as label to text() works differently when the call involves paste() vs paste0()

Hi all,

Maybe a bit of an esoteric observation, but the second one doesn't work
properly:

x <- 2
plot(NA, xlim=c(0,1), ylim=c(0,1))
text(0.5, 0.55, bquote(paste("x =", .(x))))
text(0.5, 0.45, bquote(paste0("x = ", .(x))))

Note that this has nothing to do in particular with bquote(). This is the same
issue:

plot(NA, xlim=c(0,1), ylim=c(0,1))
text(0.5, 0.55, as.call(list(quote(paste), "x =", 2)))
text(0.5, 0.45, as.call(list(quote(paste0), "x = ", 2)))

I had a look at C_text in plot.c, but couldn't figure out why the second one
is treated differently.

Best,
Wolfgang

On 05/09/2022 9:36 a.m., Viechtbauer, Wolfgang (NP)
wrote:
> Hi all,
> 
> Maybe a bit of an esoteric observation, but the second one doesn't work
properly:
> 
> x <- 2
> plot(NA, xlim=c(0,1), ylim=c(0,1))
> text(0.5, 0.55, bquote(paste("x =", .(x))))
> text(0.5, 0.45, bquote(paste0("x = ", .(x))))
> 
> Note that this has nothing to do in particular with bquote(). This is the
same issue:
> 
> plot(NA, xlim=c(0,1), ylim=c(0,1))
> text(0.5, 0.55, as.call(list(quote(paste), "x =", 2)))
> text(0.5, 0.45, as.call(list(quote(paste0), "x = ", 2)))
> 
> I had a look at C_text in plot.c, but couldn't figure out why the
second one is treated differently.
You're using plotmath code, which is documented in ?plotmath.

It doesn't execute paste(), it just uses that name for a similar 
operation.  There's no operation named paste0(), so that doesn't work.

The paste() operation doesn't add space, so it's more like paste0() in 
any case.

Duncan Murdoch