def test_parse_letrec_oddeven():
even = Expr.as_proc(["x"],
Expr.as_if(
Expr.as_iszero(Expr.as_var("x")),
Expr.as_lit(1),
Expr.as_call(
Expr.as_var("odd"),
Expr.as_diff(
Expr.as_var("x"),
Expr.as_lit(1))))).procexpr
odd = Expr.as_proc(["x"],
Expr.as_if(
Expr.as_iszero(Expr.as_var("x")),
Expr.as_lit(0),
Expr.as_call(
Expr.as_var("even"),
Expr.as_diff(
Expr.as_var("x"),
Expr.as_lit(1))))).procexpr
e2 = Expr.as_letrec({"even": even, "odd": odd},
Expr.as_call(Expr.as_var("odd"), Expr.as_lit(13)))
runtest("""
letrec
even(x) = if (isz x) then 1 else (odd -(x,1))
odd(x) = if (isz x) then 0 else (even -(x,1))
in (odd 13)
""", e2)
def test_parse_letrec_double():
e2 = Expr.as_letrec({
"double": Expr.as_proc(["x"],
Expr.as_if(Expr.as_iszero(Expr.as_var("x")),
Expr.as_lit(0),
Expr.as_diff(
Expr.as_call(Expr.as_var("double"),
Expr.as_diff(
Expr.as_var("x"),
Expr.as_lit(1))),
Expr.as_lit(-2)))).procexpr
}, Expr.as_call(Expr.as_var("double"), Expr.as_lit(6)))
runtest("""
letrec
double(x) = (if (isz x) then 0 else -((double -(x,1)), -2))
in (double 6)
""", e2)
def test_parse_diff():
e2 = Expr.as_diff(Expr.as_lit(33), Expr.as_lit(44))
runtest("- ( 33, 44)", e2)