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#!pl0
# [test.pl0] A PL0 example "program"
# first we define a few operation the hard way.
fun add(a,b) = if a = 0 then b else 1 + add(a-1,b)
fun times(a,b) = if a = 0 then 0 else add(times(a-1,b),b)
fun fact(n)
= if n = 0 then
1
else
times(n, fact(n-1))
fun profile() = fact(6)
# now try the evaluator with primitive ground expression
run 1
run 1+3
run 2*7-1
# now try the evaluator using functions
run add(0,3)
run add(1,3)
run add(7,3)
run times(7,3)
# following an example for profiling.
# It may take a moment to compute, but
# executes 2839 function calls and
# evaluates a total of 23347 expression.
# on a fast machine, you might want to
# increase the argument slightly to gain
# a visible effect. Then notice that the
# interpreter is not yet optimized for
# speed.
run profile()
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