peforth 1.31

A FORTH programming language built on python.

peforth

A programmable python debugger allows you to abruptly setup procedures to investigate your program code on the fly at a breakpoint.

You guys know how to bebug already. We all do. But when it comes to Machine Learning and Tensorflow or the likes, things are getting annoying. A programmable debugger is what in my mind and probably in yours too. One breakpoint to investigate about everything! At this point, you can then test whatever you want, supported by all the power of FORTH.

Debug commands in FORTH syntax

So now we need to choose an interactive UI and its syntax that is light weight, reliable and flexible so we won’t regret of choosing it someday, has been there for decades so many people don’t need to learn about another new language although we are only to use some debug commands, yet easy enough for new users, that’s FORTH.

Install peforth

pip install peforth

For Jupyter Notebook users, we can use FORTH language to investigate python objects through peforth magics %f and %%f. For tutorials, please find and read jupyter notebooks in the ‘notebook’ directory of this project on GitHub.

Run peforth:

Print “Hello World!”

Microsoft Windows [Version 10.0.15063]
(c) 2017 Microsoft Corporation. All rights reserved.

c:\Users\your-working-folder>python -m peforth .' Hello World!!' cr bye
Hello World!!

c:\Users\your-working-folder>

so your peforth is working fine. To your application, import peforth as usual to bring in the debugger:

c:\Users\your-working-folder>python
Python 3.6.0 (v3.6.0:41df79263a11, Dec 23 2016, 08:06:12) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import peforth
p e f o r t h    v1.07
source code http://github.com/hcchengithub/peforth
Type 'peforth.ok()' to enter forth interpreter, 'exit' to come back.

>>>

The greeing message tells us how to enter the FORTH interpreter for your debugging or investigating and how to come back to continue running your code.

Let’s try to debug a program

# 100.py

sum = 0
for i in range(100):
    sum += i
print("The sum of 1..100 is ", sum)

Run it:

c:\Users\your-working-folder>python 100.py
The sum of 1..100 is 4950

c:\Users\your-working-folder>

The result should be 5050 but it’s not! Let’s drop a breakpoint to see what’s wrong:

# 100.py with breakpoing   .----- Specify an unique command prompt to indicate where
                           |      the breakpoint is from if there are many of them
import peforth             |            .----- pass locals() at the breakpoint
sum = 0                    |            |      to our debugger
for i in range(100):       |            |               .------- use a FORTH constant
    sum += i               |            |               |        to represent the locals()
peforth.ok('my first breakpoint> ',loc=locals(),cmd="constant locals-after-the-for-loop")
print("The sum of 1..100 is ", sum)

Run again:

c:\Users\your-working-folder>python 100.py
p e f o r t h    v1.07
source code http://github.com/hcchengithub/peforth
Type 'peforth.ok()' to enter forth interpreter, 'exit' to come back.

                     .--------------- at the breakpoint, type in 'words'
                     |                command to see what have we got
my first breakpoint> words        .-------- It's a long list of 'words'
... snip .......                  |         or available commands. Don't worry, we'll use only some of them.
expected_rstack expected_stack test-result [all-pass] *** all-pass [r r] [d d] [p
p] WshShell inport OK dir keys --- locals-after-the-for-loop
                                       |
            The last one is what ------'
            we have just created throuth the breakpoint statement
            , named "locals-after-the-for-loop"

Let’s see it:

       print a carriage return at the end -------.
                          print the thing -----. |
                                               | |
my first breakpoint> locals-after-the-for-loop . cr
({'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__':
<_frozen_importlib_external.SourceFileLoader object at 0x000001DD2D737710>,
'__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins'
(built-in)>, '__file__': '100.py', '__cached__': None, 'peforth': <module 'peforth'
from 'C:\\Users\\hcche\\AppData\\Local\\Programs\\Python\\Python36\\lib\\site-packages\\pe
forth\\__init__.py'>, 'sum': 4950, 'i': 99}, {}, 'my first breakpoint> ')
my first breakpoint>    |           |                   |
                        |           |                   '--- our command
           our sum -----'           |                        prompt
                                    |                  indicates where the
        99 instead of 100 ----------'                  breakpoint is from
        this is the problem !!

Now leave the breakpoint and let the program continue:

my first breakpoint> exit
my first breakpoint> The sum of 1..100 is  4950

c:\Users\your-working-folder>

Investigate by doing experiments right at a breakpoint

When at a breakpoint in Tensorfow tutorials, I always want to make some experiments on those frustrating tf.something(tf.something(…),…) things to have a clearer understanding of them without leaving the underlying tutorial. Let’s use the above example again in another way to demonstrate how to do that with peforth:

Run peforth:

Microsoft Windows [Version 10.0.15063]
(c) 2017 Microsoft Corporation. All rights reserved.

c:\Users\your-working-folder>python
Python 3.6.0 (v3.6.0:41df79263a11, Dec 23 2016, 08:06:12) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import peforth
p e f o r t h    v1.07
source code http://github.com/hcchengithub/peforth
Type 'peforth.ok()' to enter forth interpreter, 'exit' to come back.

>>> peforth.ok()

OK   <-------- Default FORTH command prompt
OK

Assume we are at a breakpoint and we need a procedure to add 1..100 to get the sum of them. We are not sure if the procedure is correct so we need to try. Now copy the procedure from your text editor. The ` <py>...</py> ` tells the debugger that the code within is a block of in-line python. The `outport()` function outports the given `locals()` to the FORTH environment outside the in-line python block.

<py>
sum = 0
for i in range(100):
    sum += i
print("The sum of 1..100 is ", sum)
outport(locals())
</py>

It’s a block of multiple-line text strings so we press Ctrl-D to start a multiple-line input, copy-paste, and press another Ctrl-D to end the multiple-line block. Like this:

OK
OK ^D
    <py>
    sum = 0
    for i in range(100):
        sum += i
    print("The sum of 1..100 is ", sum)
    outport(locals())
    </py>
^D
The sum of 1..100 is  4950
OK

Now use the ‘words’ command to see what have we got:

OK words
code end-code \ // <selftest> </selftest> bye /// immediate stop compyle
trim indent -indent <py> </py> </pyV> words . cr help interpret-only
compile-only literal reveal privacy (create) : ; ( BL CR word ' ,
[compile] py: py> py:~ py>~ 0branch here! here swap ! @ ? >r r> r@ drop
dup over 0< + * - / 1+ 2+ 1- 2- compile if then compiling char last
version execute cls private nonprivate (space) exit ret rescan-word-hash
(') branch bool and or not (forget) AND OR NOT XOR true false "" [] {}
none >> << 0= 0> 0<> 0<= 0>= = == > < != >= <= abs max min doVar doNext
depth pick roll space [ ] colon-word create (marker) marker next abort
alias <> public nip rot -rot 2drop 2dup invert negate within ['] allot
for begin until again ahead never repeat aft else while ?stop ?dup
variable +! chars spaces .( ." .' s" s' s` does> count accept accept2
<accept> nop </accept> refill [else] [if] [then] (::) (:>) :: :> ::~
:>~ "msg"abort abort" "msg"?abort ?abort" '<text> (<text>) <text> </text>
<comment> </comment> (constant) constant value to tib. >t t@ t> [begin]
[again] [until] [for] [next] modules int float drops dropall char>ASCII
ASCII>char ASCII .s (*debug*) *debug* readTextFile writeTextFile
tib.insert sinclude include type obj>keys obj2dict stringify toString
.literal .function (dump) dump dump2ret d (see) .members .source see dos
cd slice description expected_rstack expected_stack test-result
[all-pass] *** all-pass [r r] [d d] [p p] WshShell inport OK dir keys
--- i sum
OK

Around the end of the long list after the ` --- ` marker we found ` i ` and ` sum `. They are all locals() at the point in the in-line python block. Let’s see them:

OK i . cr
99
OK sum . cr
4950
OK

Again, we found the root cause of why the sum is not 5050 because ` i ` didn’t reach to 100 as anticipated. That’s exactly how the python `range()` works and that has actually confused me many times.

Visit this project’s Wiki pages for more examples about how to view MNIST handwritten digit images at the half way of your investigating in a Tensorflow tutorial, for example, and the usages of this programmable debugger.

Have fun!

• H.C. Chen, FigTaiwan, 2019.5.22

• [e-mail]

• Just undo it!

Edited by: rst online editor