indirect-vs-inline-python

[dreftymac]

indirect-vs-inline-python

Overview

• indirect-vs-inline-python
• using cog without having to include any python in the cog_enabled_src_file

Context

• python nedbat cog
• most recent stable version as of 2023-03-11

Scenario

• developer MurrayStella wants to invoke cog on a cog_enabled_src_file
• MurrayStella wants to remove the inline python from the cog_enabled_src_file and use indirect python instead

Example

• this simple example illustrates the desired outcome
• MurrayStella wants to convert BEFORE into AFTER

BEFORE

## Simple demo just to show what we want
* just print a hello world message
* a random number of times for variability
* include a random integer for more variability

##@ [[[cog cog.out('Hello {vxx:03d} World!\n'.format(vxx=random.randint(0,999))*random.randint(1,3)) ]]]
Hello 009 World!
Hello 009 World!
##@ [[[end]]]

##@ [[[cog cog.out('Hello {vxx:03d} World!\n'.format(vxx=random.randint(0,999))*random.randint(1,3)) ]]]
Hello 371 World!
##@ [[[end]]]

AFTER

## Simple demo just to show what we want
* just print a hello world message
* a random number of times for variability
* include a random integer for more variability

##@ <cogbeg coggid="uu190hello1678463240" coguri="py003010" >
Hello 772 World!
Hello 772 World!
Hello 772 World!
##@ <cogend>

##@ <cogbeg coggid="uu195hello1678463240" coguri="py003010" >
Hello 371 World!
##@ <cogend>

Feature request

• MurrayStella would like to use the syntax style in the AFTER example instead of BEFORE
• This could be doable with a new cmd_line flag such as --idmarker= or --outputmarker=
  • this flag is similar to the --marker cmd_line flag
  • instead of changing the cog_markup_syntax as --marker does, it would instead remove the need to specify inline python with cog.out("PythonCodeHere")
  • it would allow the user to specify any arbitrary prefix and suffix to delimit a cog_code_id
  • the cog_code_id could simply reference a variable specified with the -D name=val cmd_line flag
  • this would tell cog to get the auto-generated code from the variable instead of inline python code
  • it would also allow arbitrary syntax in the cog_enabled_src_file that does not have to involve any visible python

Workaround

• MurrayStella has already implemented a hacky sadness-inducing (but functional) workaround to provide this functionality
• Workaround Steps:
  • Step001: invoke cog from within python instead of from the cmd_line
    • this allows us to do our hacky sadness-inducing postproc and preproc
    • capt="seealso" ;; href="https://github.com/nedbat/cog/issues/19#issuecomment-1464863141"
  • Step002: change the default cog_markup_syntax with the existing --marker option
    • this allows [[[cog ]]] [[[end]]] to become <cogbeg coguri= <cogend>
  • Step003: extract out all the coggid unique_ids in the cog_enabled_src_file
  • Step004: use those unique_ids to create cog-visible variables using the -D name=val cmd_line flag
  • Step005: assign python-generated output to each of those unique_ids
    • this causes sadness because it is brittle
    • the -D name=val cmd_line flag is not friendly to python-generated output that spans more than one line
    • there are hacky workarounds for this, but they are less desirable compared to a full-fledged cogscript API
  • Step006: muck around with the cog_enabled_src_file so that coggid="unique_id_here" becomes cog.out(MyPyOutputEngine.unique_id_here())
  • Step007: invoke cog
  • Step008: muck around with the cog_enabled_src_file so that cog.out(..) changes back to coggid="..."

See also

• https://www.gnu.org/software/emacs/manual/html_node/org/Radio-tables.html