evalu . nb (pt,  dicembre 2002)

Evaluate

?Evaluate

u[x_] := x

r = {x -> a + b}

uu[a_, b_] := Evaluate[u[x] /. r]

uu[1, 2]

Invece   . . .

uu2[a_, b_] := u[x] /. r

uu2[1, 2]

. . .   ma  . . .

uu3[a_, b_] := u[x] /. x -> a + b

uu3[1, 2]