```
require(graphics)
(s.e <- substitute(expression(a + b), list(a = 1))) #> expression(1 + b)
(s.s <- substitute( a + b, list(a = 1))) #> 1 + b
c(mode(s.e), typeof(s.e)) # "call", "language"
c(mode(s.s), typeof(s.s)) # (the same)
# but:
(e.s.e <- eval(s.e)) #> expression(1 + b)
c(mode(e.s.e), typeof(e.s.e)) # "expression", "expression"
substitute(x <- x + 1, list(x = 1)) # nonsense
myplot <- function(x, y)
plot(x, y, xlab = deparse(substitute(x)),
ylab = deparse(substitute(y)))
## Simple examples about lazy evaluation, etc:
f1 <- function(x, y = x) { x <- x + 1; y }
s1 <- function(x, y = substitute(x)) { x <- x + 1; y }
s2 <- function(x, y) { if(missing(y)) y <- substitute(x); x <- x + 1; y }
a <- 10
f1(a) # 11
s1(a) # 11
s2(a) # a
typeof(s2(a)) # "symbol"
```

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