Replacing Functions in the Dictionary¶
For now, there is no way to define new functions from within the Joy language. All functions (and the interpreter) all accept and return a dictionary parameter (in addition to the stack and expression) so that we can implement e.g. a function that adds new functions to the dictionary. However, there’s no function that does that. Adding a new function to the dictionary is a meta-interpreter action, you have to do it in Python, not Joy.
from notebook_preamble import D, J, V
A long trace¶
V('[23 18] average')
. [23 18] average
[23 18] . average
[23 18] . [sum 1.0 *] [size] cleave /
[23 18] [sum 1.0 *] . [size] cleave /
[23 18] [sum 1.0 *] [size] . cleave /
[23 18] [sum 1.0 *] [size] . [i] app2 [popd] dip /
[23 18] [sum 1.0 *] [size] [i] . app2 [popd] dip /
[23 18] [[sum 1.0 *] [23 18]] [i] . infra first [[size] [23 18]] [i] infra first [popd] dip /
[23 18] [sum 1.0 *] . i [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
[23 18] . sum 1.0 * [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
41 . 1.0 * [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
41 1.0 . * [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
41.0 . [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
41.0 [[23 18]] . swaack first [[size] [23 18]] [i] infra first [popd] dip /
[23 18] [41.0] . first [[size] [23 18]] [i] infra first [popd] dip /
[23 18] 41.0 . [[size] [23 18]] [i] infra first [popd] dip /
[23 18] 41.0 [[size] [23 18]] . [i] infra first [popd] dip /
[23 18] 41.0 [[size] [23 18]] [i] . infra first [popd] dip /
[23 18] [size] . i [41.0 [23 18]] swaack first [popd] dip /
[23 18] . size [41.0 [23 18]] swaack first [popd] dip /
[23 18] . 0 swap [pop ++] step [41.0 [23 18]] swaack first [popd] dip /
[23 18] 0 . swap [pop ++] step [41.0 [23 18]] swaack first [popd] dip /
0 [23 18] . [pop ++] step [41.0 [23 18]] swaack first [popd] dip /
0 [23 18] [pop ++] . step [41.0 [23 18]] swaack first [popd] dip /
0 23 [pop ++] . i [18] [pop ++] step [41.0 [23 18]] swaack first [popd] dip /
0 23 . pop ++ [18] [pop ++] step [41.0 [23 18]] swaack first [popd] dip /
0 . ++ [18] [pop ++] step [41.0 [23 18]] swaack first [popd] dip /
1 . [18] [pop ++] step [41.0 [23 18]] swaack first [popd] dip /
1 [18] . [pop ++] step [41.0 [23 18]] swaack first [popd] dip /
1 [18] [pop ++] . step [41.0 [23 18]] swaack first [popd] dip /
1 18 [pop ++] . i [41.0 [23 18]] swaack first [popd] dip /
1 18 . pop ++ [41.0 [23 18]] swaack first [popd] dip /
1 . ++ [41.0 [23 18]] swaack first [popd] dip /
2 . [41.0 [23 18]] swaack first [popd] dip /
2 [41.0 [23 18]] . swaack first [popd] dip /
[23 18] 41.0 [2] . first [popd] dip /
[23 18] 41.0 2 . [popd] dip /
[23 18] 41.0 2 [popd] . dip /
[23 18] 41.0 . popd 2 /
41.0 . 2 /
41.0 2 . /
20.5 .
Replacing size with a Python version¶
Both sum and size each convert a sequence to a single value.
sum == 0 swap [+] step
size == 0 swap [pop ++] step
An efficient sum function is already in the library. But for
size we can use a “compiled” version hand-written in Python to speed
up evaluation and make the trace more readable.
from joy.library import SimpleFunctionWrapper
from joy.utils.stack import iter_stack
@SimpleFunctionWrapper
def size(stack):
'''Return the size of the sequence on the stack.'''
sequence, stack = stack
n = 0
for _ in iter_stack(sequence):
n += 1
return n, stack
Now we replace the old version in the dictionary with the new version, and re-evaluate the expression.
D['size'] = size
A shorter trace¶
You can see that size now executes in a single step.
V('[23 18] average')
. [23 18] average
[23 18] . average
[23 18] . [sum 1.0 *] [size] cleave /
[23 18] [sum 1.0 *] . [size] cleave /
[23 18] [sum 1.0 *] [size] . cleave /
[23 18] [sum 1.0 *] [size] . [i] app2 [popd] dip /
[23 18] [sum 1.0 *] [size] [i] . app2 [popd] dip /
[23 18] [[sum 1.0 *] [23 18]] [i] . infra first [[size] [23 18]] [i] infra first [popd] dip /
[23 18] [sum 1.0 *] . i [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
[23 18] . sum 1.0 * [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
41 . 1.0 * [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
41 1.0 . * [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
41.0 . [[23 18]] swaack first [[size] [23 18]] [i] infra first [popd] dip /
41.0 [[23 18]] . swaack first [[size] [23 18]] [i] infra first [popd] dip /
[23 18] [41.0] . first [[size] [23 18]] [i] infra first [popd] dip /
[23 18] 41.0 . [[size] [23 18]] [i] infra first [popd] dip /
[23 18] 41.0 [[size] [23 18]] . [i] infra first [popd] dip /
[23 18] 41.0 [[size] [23 18]] [i] . infra first [popd] dip /
[23 18] [size] . i [41.0 [23 18]] swaack first [popd] dip /
[23 18] . size [41.0 [23 18]] swaack first [popd] dip /
2 . [41.0 [23 18]] swaack first [popd] dip /
2 [41.0 [23 18]] . swaack first [popd] dip /
[23 18] 41.0 [2] . first [popd] dip /
[23 18] 41.0 2 . [popd] dip /
[23 18] 41.0 2 [popd] . dip /
[23 18] 41.0 . popd 2 /
41.0 . 2 /
41.0 2 . /
20.5 .
