docs: micropython.viper: number of arguments in functions

[massimosala]

From the official doc https://docs.micropython.org/en/v1.9.3/pyboard/reference/speed_python.html#the-viper-code-emitter

In addition to the restrictions imposed by the native emitter the following constraints apply:

• Functions may have up to four arguments

Well, I am using a function with 7 arguments... and it works.

I tested the crc calculation with 19 different polynomials, input data "123456789" and the expected results published here
https://crccalc.com/

@micropython.viper
def crc_msb(shift: uint, data: ptr8, ldata: int, init: uint, poly: uint, xor_in: uint = 0, xor_out: uint = 0) -> uint :
...

Mmh to be sure, how do you suggest to check if the function is running optimized or not?
(preferably a method not depending on execution times).

Is it the documentation up-to-date?

[rkompass]

Already in MP 1.14 apparently there is no limit any longer. Just tested 13 arguments.

# Here we investigate how many arguments a viper function may have

@micropython.viper
def sum4(x0:int, x1:int, x2:int, x3:int) -> int:
    return x0+x1+x2+x3

@micropython.viper
def sum5(x0:int, x1:int, x2:int, x3:int, x4:int) -> int:
    return x0+x1+x2+x3+x4

@micropython.viper
def sum6(x0:int, x1:int, x2:int, x3:int, x4:int, x5:int) -> int:
    return x0+x1+x2+x3+x4+x5

@micropython.viper
def sum7(x0:int, x1:int, x2:int, x3:int, x4:int, x5:int, x6:int) -> int:
    return x0+x1+x2+x3+x4+x5+x6

@micropython.viper
def sum8(x0:int, x1:int, x2:int, x3:int, x4:int, x5:int, x6:int, x7:int) -> int:
    return x0+x1+x2+x3+x4+x5+x6+x7

@micropython.viper
def sum9(x0:int, x1:int, x2:int, x3:int, x4:int, x5:int, x6:int, x7:int, x8:int) -> int:
    return x0+x1+x2+x3+x4+x5+x6+x7+x8

@micropython.viper
def sum10(x0:int, x1:int, x2:int, x3:int, x4:int, x5:int, x6:int, x7:int, x8:int, x9:int) -> int:
    return x0+x1+x2+x3+x4+x5+x6+x7+x8+x9

@micropython.viper
def sum11(x0:int, x1:int, x2:int, x3:int, x4:int, x5:int, x6:int, x7:int, x8:int, x9:int, x10:int) -> int:
    return x0+x1+x2+x3+x4+x5+x6+x7+x8+x9+x10

@micropython.viper
def sum12(x0:int, x1:int, x2:int, x3:int, x4:int, x5:int, x6:int, x7:int, x8:int, x9:int, x10:int, x11:int) -> int:
    return x0+x1+x2+x3+x4+x5+x6+x7+x8+x9+x10+x11

@micropython.viper
def sum13(x0:int, x1:int, x2:int, x3:int, x4:int, x5:int, x6:int, x7:int, x8:int, x9:int, x10:int, x11:int, x12:int) -> int:
    return x0+x1+x2+x3+x4+x5+x6+x7+x8+x9+x10+x11+x12

print('sum4(1,2,3,4) = ', end='')
print(sum4(1,2,3,4))
print('sum5(1,2,3,4,5) = ', end='')
print(sum5(1,2,3,4,5))
print('sum6(1,2,3,4,5,6) = ', end='')
print(sum6(1,2,3,4,5,6))
print('sum7(1,2,3,4,5,6,7) = ', end='')
print(sum7(1,2,3,4,5,6,7))
print('sum8(1,2,3,4,5,6,7,8) = ', end='')
print(sum8(1,2,3,4,5,6,7,8))
print('sum9(1,2,3,4,5,6,7,8,9) = ', end='')
print(sum9(1,2,3,4,5,6,7,8,9))
print('sum10(1,2,3,4,5,6,7,8,9,10) = ', end='')
print(sum10(1,2,3,4,5,6,7,8,9,10))
print('sum11(1,2,3,4,5,6,7,8,9,10,11) = ', end='')
print(sum11(1,2,3,4,5,6,7,8,9,10,11))
print('sum12(1,2,3,4,5,6,7,8,9,10,11,12) = ', end='')
print(sum12(1,2,3,4,5,6,7,8,9,10,11,12))
print('sum13(1,2,3,4,5,6,7,8,9,10,11,12,13) = ', end='')
print(sum13(1,2,3,4,5,6,7,8,9,10,11,12,13))

gives:

sum4(1,2,3,4) = 10
sum5(1,2,3,4,5) = 15
sum6(1,2,3,4,5,6) = 21
sum7(1,2,3,4,5,6,7) = 28
sum8(1,2,3,4,5,6,7,8) = 36
sum9(1,2,3,4,5,6,7,8,9) = 45
sum10(1,2,3,4,5,6,7,8,9,10) = 55
sum11(1,2,3,4,5,6,7,8,9,10,11) = 66
sum12(1,2,3,4,5,6,7,8,9,10,11,12) = 78
sum13(1,2,3,4,5,6,7,8,9,10,11,12,13) = 91

i.e. it works as 'not yet' :-) expected. Was it stated in some version announcement that the restriction is lifted?
So the doc is not up to date (you refer to an older version, but its similar on the currenct doc).

[peterhinch]

Wow! Thanks for that. I've been working round the four arg limit for years...

You can view the emitted bytecode with the Unix build:

& micropython -v -v foo.py

In the case of a Viper function there is no bytecode (native code is emitted), but you can see the difference with and without the Viper decorator.

[jimmo]

I went spelunking and turns out that limitation was removed nearly five years ago! (I didn't know either!)

Created #11564 to fix the docs.

[dpgeorge]

Docs fixed merged in 0000eb2