py: Fix bug in optimised for .. range.
Don't store final, failing value to the loop variable. This fix also makes for .. range a bit more efficient, as it uses less store/load pairs for the loop variable.
This commit is contained in:
Damien George
parent
8cd72bdf92
commit
3ff2d03891
23
py/compile.c
23
py/compile.c
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@ -1534,35 +1534,41 @@ void compile_while_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
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}
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// TODO preload end and step onto stack if they are not constants
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// TODO check if step is negative and do opposite test
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// Note that, as per semantics of for .. range, the final failing value should not be stored in the loop variable
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// And, if the loop never runs, the loop variable should never be assigned
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void compile_for_stmt_optimised_range(compiler_t *comp, mp_parse_node_t pn_var, mp_parse_node_t pn_start, mp_parse_node_t pn_end, mp_parse_node_t pn_step, mp_parse_node_t pn_body, mp_parse_node_t pn_else) {
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START_BREAK_CONTINUE_BLOCK
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int top_label = comp_next_label(comp);
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int entry_label = comp_next_label(comp);
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// compile: var = start
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// compile: start, duplicated on stack
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compile_node(comp, pn_start);
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c_assign(comp, pn_var, ASSIGN_STORE);
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EMIT(dup_top);
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EMIT_ARG(jump, entry_label);
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EMIT_ARG(label_assign, top_label);
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// at this point we actually have 1 less element on the stack
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EMIT_ARG(set_stack_size, EMIT(get_stack_size) - 1);
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// store next value to var
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c_assign(comp, pn_var, ASSIGN_STORE);
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// compile body
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compile_node(comp, pn_body);
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EMIT_ARG(label_assign, continue_label);
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// compile: var += step
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c_assign(comp, pn_var, ASSIGN_AUG_LOAD);
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// compile: var + step, duplicated on stack
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compile_node(comp, pn_var);
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compile_node(comp, pn_step);
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EMIT_ARG(binary_op, MP_BINARY_OP_INPLACE_ADD);
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c_assign(comp, pn_var, ASSIGN_AUG_STORE);
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EMIT(dup_top);
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EMIT_ARG(label_assign, entry_label);
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// compile: if var <cond> end: goto top
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compile_node(comp, pn_var);
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compile_node(comp, pn_end);
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assert(MP_PARSE_NODE_IS_SMALL_INT(pn_step));
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if (MP_PARSE_NODE_LEAF_SMALL_INT(pn_step) >= 0) {
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@ -1572,6 +1578,9 @@ void compile_for_stmt_optimised_range(compiler_t *comp, mp_parse_node_t pn_var,
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}
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EMIT_ARG(pop_jump_if_true, top_label);
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// discard final value of var that failed the loop condition
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EMIT(pop_top);
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// break/continue apply to outer loop (if any) in the else block
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END_BREAK_CONTINUE_BLOCK
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@ -0,0 +1,8 @@
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i = 'init'
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for i in range(0):
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pass
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print(i) # should not have been modified
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for i in range(10):
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pass
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print(i) # should be last successful value of loop
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@ -0,0 +1,159 @@
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# mad.py
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# Alf Clement 27-Mar-2014
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#
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zero=0
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three=3
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print("1")
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print("2")
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print(three)
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print("{}".format(4))
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five=25/5
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print(int(five))
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j=0
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for i in range(4):
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j += i
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print(j)
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print(3+4)
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try:
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a=4/zero
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except:
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print(8)
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print("xxxxxxxxx".count("x"))
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def ten():
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return 10
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print(ten())
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a=[]
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for i in range(13):
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a.append(i)
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print(a[11])
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print(a[-1])
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str="0123456789"
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print(str[1]+str[3])
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def p(s):
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print(s)
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p("14")
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p(15)
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class A:
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def __init__(self):
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self.a=16
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def print(self):
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print(self.a)
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def set(self,b):
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self.a=b
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a=A()
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a.print()
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a.set(17)
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a.print()
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b=A()
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b.set(a.a + 1)
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b.print()
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for i in range(20):
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pass
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print(i)
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if 20 > 30:
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a="1"
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else:
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a="2"
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if 0 < 4:
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print(a+"0")
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else:
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print(a+"1")
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a=[20,21,22,23,24]
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for i in a:
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if i < 21:
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continue
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if i > 21:
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break
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print(i)
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b=[a,a,a]
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print(b[1][2])
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print(161//7)
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a=24
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while True:
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try:
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def gcheck():
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global a
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print(a)
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gcheck()
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class c25():
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x=25
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x=c25()
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print(x.x)
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raise
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except:
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print(26)
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print(27+zero)
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break
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print(28)
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k=29
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def f():
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global k
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k = yield k
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print(next(f()))
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while True:
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k+= 1
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if k < 30:
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continue
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break
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print(k)
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for i in [1,2,3]:
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class A():
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def __init__(self, c):
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self.a = i+10*c
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b = A(3)
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print(b.a)
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print(34)
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p=0
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for i in range(35, -1, -1):
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print(i)
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p = p + 1
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if p > 0:
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break
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p=36
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while p == 36:
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print(p)
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p=37
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print(p)
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for i in [38]:
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print(i)
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print(int(exec("def foo(): return 38") == None)+foo())
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d = {}
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exec("def bar(): return 40", d)
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print(d["bar"]())
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def fib2(n):
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result = []
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a, b = 0, 1
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while a < n:
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result.append(a)
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a, b = b, a+b
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return result
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print(fib2(100)[-2]-14)
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Answer={}
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Answer["ForAll"]=42
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print(Answer["ForAll"])
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i = 43
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def f(i=i):
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print(i)
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i = 44
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f()
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print(i)
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while True:
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try:
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if None != True:
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print(45)
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break
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else:
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print(0)
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except:
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print(0)
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print(46)
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print(46+1)
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def u(p):
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if p > 3:
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return 3*p
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else:
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return u(2*p)-3*u(p)
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print(u(16))
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def u49():
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return 49
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print(u49())
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