4 ms·

I'm wondering if anyone has tried to use another language - I'm thinking Ruby - as a pre-processor for C++ code. I know people have pre-processed C++ code with

by daemin 9y ago

I'm wondering if anyone has tried to use another language - I'm thinking Ruby - as a pre-processor for C++ code. I know people have pre-processed C++ code with various tools - for example Qt - but I'm thinking of just replacing # pre-processor statements with something like Rails based templates.

AlbertoGP 9y ago
I used Python to generate C++ with a utility I wrote called "PythonPP": http://matracas.org/utiles/index.html.en http://matracas.org/utiles/index.html.en One of the things it did was to generate the function prototypes so that a typical .h file would look like this: #!from base_cc import * #""// Clase: ${project_part_name} #""// Proyecto: ${project_name} #!import time #""// Fecha: ${time.strftime("%A, %d de %B de %Y, %H:%M:%S %Z", time.localtime(time.time()))} #""${cc_copyright_notice("GPL", "2001, 2002, 2003, 2007, 2010")} #""#ifndef _H_${project_part_name} #""#define _H_${project_part_name} #""${cc_function_includes_for_class()} #""${cc_variable_global_declarations_for_class()} #""class ${project_part_name} { #""${cc_variable_declarations_for_class()} #""${cc_function_protos_for_class()} }; #""${cc_operator_protos_for_class()} #endif The .cc file was similar, calling Python functions to get the function definitions from separate files: I built one directory for each class, where I would put each big function or several related small functions in its own file, and they would be found and combined automatically. For each class, there was a vars.cc file which contained member variables, with their declaration line, initialization and destruction in consecutive lines: the declaration went to the .h file, the initialization to the constructor, and the destruction to the destructor. This way I avoided forgetting to release something and had a good overview of all variables and their life cycles. Here is an example of generating constant names from a Python list: #!for token_id in lexer_table: #" " case TOKEN_ID_${token_id[1]}: #' ' cerr << "\n --- [" << index_of_current_character #" " << "] TOKEN_ID_${token_id[1]} '" << buffer << "'" #' ' << endl << flush; #' ' break; The same idea was also used in the Bison/Yacc grammar file: #!%token <markup> T_QMATH_DIRECTIVE %token <markup> T_DIRECTIVE_DEFINITION %token <markup> T_DIRECTIVE_CONTEXT for d in qmath_directives: #" "%token <markup> T_DIRECTIVE_${d.upper()} I've used it also for other languages like Java where it cuts down the boilerplate. For instance, the package names are automatically generated from the file path.
notalaser 9y ago
I've seen it done (on a large-ish codebase), using Perl as a preprocessor for C. It looked good on paper and we were really enthusiastic when we came up with the idea, but it quickly degenerated into the proverbial ad-hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp. In retrospect, we could have done worse, like use C++ :-).
Keyframe 9y ago
M4 was/is quite popular.
Pete_D 9y ago
A while ago, in a fit of defmacro-envy, I wrote a preprocessor that would let you wrap Python snippets in #python/#endpython blocks: http://codepad.org/5B388Wsh http://codepad.org/5B388Wsh. This lets you write silly things like http://codepad.org/eS443WPA http://codepad.org/eS443WPA. I bet the same idea isn't too hard to implement in Ruby, but I don't know enough to try it myself. I never really used it much - generating C code with Python print statements turned out to look uglier than I thought it would, and most of my use cases were better handled with X macros (https://en.wikipedia.org/wiki/X_Macro https://en.wikipedia.org/wiki/X_Macro) or by generating a separate file and #include'ing it. But your description reminded me of it; you might like the idea.

by daemin 9y ago

AlbertoGP 9y ago

I used Python to generate C++ with a utility I wrote called "PythonPP": http://matracas.org/utiles/index.html.en http://matracas.org/utiles/index.html.en One of the things it did was to generate the function prototypes so that a typical .h file would look like this: #!from base_cc import * #""// Clase: ${project_part_name} #""// Proyecto: ${project_name} #!import time #""// Fecha: ${time.strftime("%A, %d de %B de %Y, %H:%M:%S %Z", time.localtime(time.time()))} #""${cc_copyright_notice("GPL", "2001, 2002, 2003, 2007, 2010")} #""#ifndef _H_${project_part_name} #""#define _H_${project_part_name} #""${cc_function_includes_for_class()} #""${cc_variable_global_declarations_for_class()} #""class ${project_part_name} { #""${cc_variable_declarations_for_class()} #""${cc_function_protos_for_class()} }; #""${cc_operator_protos_for_class()} #endif The .cc file was similar, calling Python functions to get the function definitions from separate files: I built one directory for each class, where I would put each big function or several related small functions in its own file, and they would be found and combined automatically. For each class, there was a vars.cc file which contained member variables, with their declaration line, initialization and destruction in consecutive lines: the declaration went to the .h file, the initialization to the constructor, and the destruction to the destructor. This way I avoided forgetting to release something and had a good overview of all variables and their life cycles. Here is an example of generating constant names from a Python list: #!for token_id in lexer_table: #" " case TOKEN_ID_${token_id[1]}: #' ' cerr << "\n --- [" << index_of_current_character #" " << "] TOKEN_ID_${token_id[1]} '" << buffer << "'" #' ' << endl << flush; #' ' break; The same idea was also used in the Bison/Yacc grammar file: #!%token <markup> T_QMATH_DIRECTIVE %token <markup> T_DIRECTIVE_DEFINITION %token <markup> T_DIRECTIVE_CONTEXT for d in qmath_directives: #" "%token <markup> T_DIRECTIVE_${d.upper()} I've used it also for other languages like Java where it cuts down the boilerplate. For instance, the package names are automatically generated from the file path.

notalaser 9y ago

I've seen it done (on a large-ish codebase), using Perl as a preprocessor for C. It looked good on paper and we were really enthusiastic when we came up with the idea, but it quickly degenerated into the proverbial ad-hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp. In retrospect, we could have done worse, like use C++ :-).

Keyframe 9y ago

M4 was/is quite popular.

Pete_D 9y ago

A while ago, in a fit of defmacro-envy, I wrote a preprocessor that would let you wrap Python snippets in #python/#endpython blocks: http://codepad.org/5B388Wsh http://codepad.org/5B388Wsh. This lets you write silly things like http://codepad.org/eS443WPA http://codepad.org/eS443WPA. I bet the same idea isn't too hard to implement in Ruby, but I don't know enough to try it myself. I never really used it much - generating C code with Python print statements turned out to look uglier than I thought it would, and most of my use cases were better handled with X macros (https://en.wikipedia.org/wiki/X_Macro https://en.wikipedia.org/wiki/X_Macro) or by generating a separate file and #include'ing it. But your description reminded me of it; you might like the idea.