# The result I am after is the result after a substitution in an expression, such as

substitute(expression(a+b+c), list(a=1))
expression(1 + b + c)
 # However, the way I want to do it is for a an expression "stored as a variable" as

(expr <- expression(a+b+c))
expression(a + b + c)
 # a) The following does not work

(expr2 <- substitute(expr, list(a=1)))
expr
 # b) - whereas this does work:

ans <- eval(substitute(substitute(qqq, list(a=1)), list(qqq=expr[[1]])))
as.expression(ans)
expression(1 + b + c)
 # I have - at least - two problems:
# I am not sure I understand 1) why a) does not work and 2) why b) does work.
# Can anyone point me in the right direction?

# Thanks
# Søren

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