geda:gnetlist_scheme_tutorial
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geda:gnetlist_scheme_tutorial [2012/02/20 15:14] 127.0.0.1 external edit |
geda:gnetlist_scheme_tutorial [2015/10/17 17:53] svennb |
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| + | //Translations of this page are also available in the following languages:// [[gnetlist_scheme_tutorial.ru|Русский]]. | ||
| + | |||
| ====== Scripting a gnetlist backend in Scheme ====== | ====== Scripting a gnetlist backend in Scheme ====== | ||
| **by John Doty** | **by John Doty** | ||
| - | (this was [[http://archives.seul.org/geda/user/Jul-2009/msg00235.html|originally posted]] to the gEDA-user mailing list in July 2009) | + | (this was [[http://archives.seul.org/geda/user/Jul-2009/msg00235.html|originally posted]] to the gEDA-user mailing list in July 2009) |
| Don't Panic! | Don't Panic! | ||
| - | If you've never written a program in Lisp, it looks daunting. But it's a lot easier than it looks. Wrap a little bit of "syntactic | + | If you've never written a program in Lisp, it looks daunting. But it's a lot easier than it looks. Wrap a little bit of "syntactic |
| sugar" around Lisp, and it becomes Logo, which elementary school children can learn. | sugar" around Lisp, and it becomes Logo, which elementary school children can learn. | ||
| - | And, just to make it clear what some of the funny words mean, [[wp>Lisp_(programming_language)|Lisp]] is a computer language, [[wp>Scheme_(programming_language)|Scheme]] is a dialect of Lisp, and [[wp>GNU_Guile|Guile]] is an | + | And, just to make it clear what some of the funny words mean, [[wp>Lisp_(programming_language)|Lisp]] is a computer language, [[wp>Scheme_(programming_language)|Scheme]] is a dialect of Lisp, and [[wp>GNU_Guile|Guile]] is an |
| - | implementation of Scheme. Guile is used for "scripting" gEDA. In particular, the gnetlist front end, written in C, extracts topology | + | implementation of Scheme. Guile is used for "scripting" gEDA. In particular, the gnetlist front end, written in C, extracts topology |
| and attribute information from schematics, and then presents that data to "back end" Guile scripts for processing and output. | and attribute information from schematics, and then presents that data to "back end" Guile scripts for processing and output. | ||
| - | This tutorial is specifically about programming gnetlist back ends in Scheme. If you don't already know Scheme, you should probably look at | + | This tutorial is specifically about programming gnetlist back ends in Scheme. If you don't already know Scheme, you should probably look at |
| other material too, such as: | other material too, such as: | ||
| Line 29: | Line 31: | ||
| OK, let's get started. Here's a particularly simple back end: | OK, let's get started. Here's a particularly simple back end: | ||
| - | <code scheme> | + | <code lisp> |
| ;; gnetlist development playground | ;; gnetlist development playground | ||
| Line 40: | Line 42: | ||
| </code> | </code> | ||
| - | To use this, put it in a file called ''gnet-devel.scm''. Copy this file | + | To use this, put it in a file called ''gnet-devel.scm''. Copy this file |
| - | to wherever gnetlist Scheme files are kept on your system. On the | + | to wherever gnetlist Scheme files are kept on your system. On the |
| machine I'm using today, the command is: | machine I'm using today, the command is: | ||
| Line 70: | Line 72: | ||
| You should see: | You should see: | ||
| - | <code scheme> | + | <code lisp> |
| ("Q3" "R5" "Q2" "R4" "Q1" "C6" "R3" "L2" "A1" "bat(+3v)" "lamp(1)" "R2" "C5" "L1" "R1" "C4" "lamp(2)" "C3" "C2" "C1" "D1" "bat(0v)" "R7" "Q4" "R6") | ("Q3" "R5" "Q2" "R4" "Q1" "C6" "R3" "L2" "A1" "bat(+3v)" "lamp(1)" "R2" "C5" "L1" "R1" "C4" "lamp(2)" "C3" "C2" "C1" "D1" "bat(0v)" "R7" "Q4" "R6") | ||
| </code> | </code> | ||
| - | ''"packages"'' is a handy variable, containing a list of all unique ''"refdes="'' attribute values. By typing it, you fed it to the "REPL", | + | ''"packages"'' is a handy variable, containing a list of all unique ''"refdes="'' attribute values. By typing it, you fed it to the "REPL", |
| the Read, Evaluate, Print Loop. So, the REPL read it, evaluated it (getting a list), and printed it. | the Read, Evaluate, Print Loop. So, the REPL read it, evaluated it (getting a list), and printed it. | ||
| Line 84: | Line 86: | ||
| </code> | </code> | ||
| - | What happened here? Here, the REPL evaluated the list | + | What happened here? Here, the REPL evaluated the list |
| - | <code scheme> | + | <code lisp> |
| (length packages) | (length packages) | ||
| </code> | </code> | ||
| Line 112: | Line 114: | ||
| The readline stuff in our ''gnet-devel.scm'' back end allows you to use the cursor keys on your keyboard to move around through the history and edit input. Very handy when interacting. Try it. | The readline stuff in our ''gnet-devel.scm'' back end allows you to use the cursor keys on your keyboard to move around through the history and edit input. Very handy when interacting. Try it. | ||
| - | Another useful variable gnetlist defines is ''"all-unique-nets"'' (type it). Just as ''"(length packages)"'' tells you how many packages you | + | Another useful variable gnetlist defines is ''"all-unique-nets"'' (type it). Just as ''"(length packages)"'' tells you how many packages you |
| have, ''"(length all-unique-nets)"'' will tell you how many nets you have. | have, ''"(length all-unique-nets)"'' will tell you how many nets you have. | ||
| Line 145: | Line 147: | ||
| (apply p x) calls procedure p once, with all of the elements of x as arguments. So the expression above winds up evaluating: | (apply p x) calls procedure p once, with all of the elements of x as arguments. So the expression above winds up evaluating: | ||
| - | <code scheme> | + | <code lisp> |
| (+ 3 3 2 2 2 2 2 2 2 2 2 2 2 2 1 1 2 3 3 1 2 3 2 1 1) | (+ 3 3 2 2 2 2 2 2 2 2 2 2 2 2 1 1 2 3 3 1 2 3 2 1 1) | ||
| </code> | </code> | ||
| Line 171: | Line 173: | ||
| Now we can put our statistics collection together into a back end. First, define a procedure to write a line of output: | Now we can put our statistics collection together into a back end. First, define a procedure to write a line of output: | ||
| - | <code scheme> | + | <code lisp> |
| (define format-line | (define format-line | ||
| (lambda (name value) | (lambda (name value) | ||
| Line 183: | Line 185: | ||
| We're using two new builtin procedures here, ''"display"'' and ''"newline"'', which should be self-explanatory. Now: | We're using two new builtin procedures here, ''"display"'' and ''"newline"'', which should be self-explanatory. Now: | ||
| - | <code scheme> | + | <code lisp> |
| (define display-stats | (define display-stats | ||
| (lambda () ; no arguments | (lambda () ; no arguments | ||
| Line 202: | Line 204: | ||
| To finish off a back end, we need a "main program". By convention, that has the name of the back end. It has the responsibility of opening the output file, too. So, for a "stats" back end for collecting the stats, the entire file looks like: | To finish off a back end, we need a "main program". By convention, that has the name of the back end. It has the responsibility of opening the output file, too. So, for a "stats" back end for collecting the stats, the entire file looks like: | ||
| - | <code scheme> | + | <code lisp> |
| ;; gnetlist back end for extracting design statistics | ;; gnetlist back end for extracting design statistics | ||
| ;; | ;; | ||
| Line 235: | Line 237: | ||
| </code> | </code> | ||
| - | Put this in a file named ''gnet-stats.scm'', copy it to where it belongs with something like | + | Put this in a file named ''gnet-stats.scm'', copy it to where it belongs with something like |
| <code bash> | <code bash> | ||
| $ sudo cp gnet-stats.scm /sw/share/gEDA/scheme/ | $ sudo cp gnet-stats.scm /sw/share/gEDA/scheme/ | ||
| </code> | </code> | ||
| - | and then ''"gnetlist -g stats"'' followed by the usual other arguments and schematic pathnames will put your design's statistics in the | + | and then ''"gnetlist -g stats"'' followed by the usual other arguments and schematic pathnames will put your design's statistics in the |
| output file (default ''output.net''). | output file (default ''output.net''). | ||
| - | Pretty easy, huh? Useful, too. Lately I've been designing systems that consist of stacks of boards: statistics like these are helpful | + | Pretty easy, huh? Useful, too. Lately I've been designing systems that consist of stacks of boards: statistics like these are helpful |
| in figuring out which subsystems I should combine on each board. | in figuring out which subsystems I should combine on each board. | ||
| + | ====== See also ====== | ||
| + | |||
| + | * [[geda:guile_scripting]] | ||
| + | * [[geda:gnetlist_scheme_primitives]] | ||
geda/gnetlist_scheme_tutorial.txt · Last modified: 2015/10/17 17:53 by svennb
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