138 lines
5.1 KiB
Markdown
138 lines
5.1 KiB
Markdown
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### Preamble
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First, import what we need.
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```python
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from joy.joy import run
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from joy.library import initialize
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from joy.utils.stack import stack_to_string
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from joy.utils.pretty_print import TracePrinter
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```
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Define a dictionary, an initial stack, and two helper functions to run Joy code and print results for us.
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```python
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D = initialize()
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S = ()
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def J(text):
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print stack_to_string(run(text, S, D)[0])
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def V(text):
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tp = TracePrinter()
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run(text, S, D, tp.viewer)
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tp.print_()
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```
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### Run some simple programs
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```python
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J('23 18 +')
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```
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41
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```python
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J('45 30 gcd')
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```
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15
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### With Viewer
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A `viewer` records each step of the evaluation of a Joy program. The `TracePrinter` has a facility for printing out a trace of the evaluation, one line per step. Each step is aligned to the current interpreter position, signified by a period separating the stack on the left from the pending expression ("continuation") on the right. I find these traces beautiful, like a kind of art.
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```python
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V('23 18 +')
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```
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. 23 18 +
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23 . 18 +
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23 18 . +
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41 .
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```python
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V('45 30 gcd')
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```
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. 45 30 gcd
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45 . 30 gcd
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45 30 . gcd
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45 30 . 1 [tuck modulus dup 0 >] loop pop
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45 30 1 . [tuck modulus dup 0 >] loop pop
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45 30 1 [tuck modulus dup 0 >] . loop pop
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45 30 . tuck modulus dup 0 > [tuck modulus dup 0 >] loop pop
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30 45 30 . modulus dup 0 > [tuck modulus dup 0 >] loop pop
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30 15 . dup 0 > [tuck modulus dup 0 >] loop pop
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30 15 15 . 0 > [tuck modulus dup 0 >] loop pop
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30 15 15 0 . > [tuck modulus dup 0 >] loop pop
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30 15 True . [tuck modulus dup 0 >] loop pop
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30 15 True [tuck modulus dup 0 >] . loop pop
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30 15 . tuck modulus dup 0 > [tuck modulus dup 0 >] loop pop
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15 30 15 . modulus dup 0 > [tuck modulus dup 0 >] loop pop
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15 0 . dup 0 > [tuck modulus dup 0 >] loop pop
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15 0 0 . 0 > [tuck modulus dup 0 >] loop pop
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15 0 0 0 . > [tuck modulus dup 0 >] loop pop
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15 0 False . [tuck modulus dup 0 >] loop pop
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15 0 False [tuck modulus dup 0 >] . loop pop
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15 0 . pop
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15 .
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Here's a longer trace.
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```python
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V('96 27 gcd')
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```
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. 96 27 gcd
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96 . 27 gcd
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96 27 . gcd
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96 27 . 1 [tuck modulus dup 0 >] loop pop
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96 27 1 . [tuck modulus dup 0 >] loop pop
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96 27 1 [tuck modulus dup 0 >] . loop pop
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96 27 . tuck modulus dup 0 > [tuck modulus dup 0 >] loop pop
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27 96 27 . modulus dup 0 > [tuck modulus dup 0 >] loop pop
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27 15 . dup 0 > [tuck modulus dup 0 >] loop pop
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27 15 15 . 0 > [tuck modulus dup 0 >] loop pop
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27 15 15 0 . > [tuck modulus dup 0 >] loop pop
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27 15 True . [tuck modulus dup 0 >] loop pop
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27 15 True [tuck modulus dup 0 >] . loop pop
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27 15 . tuck modulus dup 0 > [tuck modulus dup 0 >] loop pop
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15 27 15 . modulus dup 0 > [tuck modulus dup 0 >] loop pop
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15 12 . dup 0 > [tuck modulus dup 0 >] loop pop
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15 12 12 . 0 > [tuck modulus dup 0 >] loop pop
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15 12 12 0 . > [tuck modulus dup 0 >] loop pop
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15 12 True . [tuck modulus dup 0 >] loop pop
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15 12 True [tuck modulus dup 0 >] . loop pop
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15 12 . tuck modulus dup 0 > [tuck modulus dup 0 >] loop pop
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12 15 12 . modulus dup 0 > [tuck modulus dup 0 >] loop pop
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12 3 . dup 0 > [tuck modulus dup 0 >] loop pop
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12 3 3 . 0 > [tuck modulus dup 0 >] loop pop
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12 3 3 0 . > [tuck modulus dup 0 >] loop pop
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12 3 True . [tuck modulus dup 0 >] loop pop
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12 3 True [tuck modulus dup 0 >] . loop pop
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12 3 . tuck modulus dup 0 > [tuck modulus dup 0 >] loop pop
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3 12 3 . modulus dup 0 > [tuck modulus dup 0 >] loop pop
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3 0 . dup 0 > [tuck modulus dup 0 >] loop pop
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3 0 0 . 0 > [tuck modulus dup 0 >] loop pop
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3 0 0 0 . > [tuck modulus dup 0 >] loop pop
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3 0 False . [tuck modulus dup 0 >] loop pop
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3 0 False [tuck modulus dup 0 >] . loop pop
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3 0 . pop
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3 .
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