Software necromancy with Perl Dave Lambley dlambley@cpan.org - PowerPoint PPT Presentation

Software necromancy with Perl Dave Lambley dlambley@cpan.org

Accounting software

Informix C-ISAM

1987 ● Perl 1.0 ● GCC 1.0

TPS report example

Historic 4GL ● Variables bound to database fields. ● Schema defined outside code using UI. ● Weakish types.

Implied dualvars, predating Perl’s?

Regexp::Grammars ● Perl 5.10 recursive regexps. ● Build a parser from familiar regexps. ● No separate lexical analysis. ● Mis-parses are slow and hard to debug

a s s i g n m e n t c o n s t a n t l v a l u e c o n s t a n t = 0 i d e n t i fj e r = t p s _ r e p o r t _ i d

a s s i g n m e n t c o n s t a n t l v a l u e c o n s t a n t = 0 i d e n t i fj e r = t p s _ r e p o r t _ i d

Regexp::Grammars

s

S e t a c c u m u l a t o r o n t p s _ s t a t u s C o m p a r i s o n I d e n t i fj e r = t p s _ s t a t u s e q 1 S e t a c c u m u l a t o r C o n s t a n t = 1 F o l l o w i n g l i n e s e t t p s _ n u m A d d t o a c c u m u l a t o r I d e n t i fj e r = t p s _ n u m + 1 Mu l t i p l y a c c u m u l a t o r C o n s t a n t = 1 * 3 S t o r e i n v a r i a b l e C o n s t a n t = 3 = t p s _ n u m S e t a c c u m u l a t o r I d e n t i fj e r = t p s _ n u m s e t t p s _ c h e c k o u t A d d t o a c c u m u l a t o r I d e n t i fj e r = t p s _ c h e c k o u t + 1 S t o r e i n v a r i a b l e C o n s t a n t = 1 = t p s _ c h e c k e d I d e n t i fj e r = t p s _ c h e c k e d

Phases ● Preprocess text (join line continuations, remove comments. ● Parse lines to parse tree. ● Flatten parse tree to op list. ● Execute op list.

In summary ● Laziness as a virtue predates Perl 1.0.

But next ● Is Perl dead? ● Is the Perl demoscene dead?

Presenting demo#1 ● Code by DLAMBLEY of CPAN. ● Grafix by .. no-one. ● Music by no-one.

Demos and games need hardware Sources: CSG and Acorn Computer

Source: https://www.khronos.org/opengl/wiki/Rendering_Pipeline_Overview

OpenGL ● SDL.pm recommends OpenGL.pm. ● OpenGL.pm gives you most of OpenGL 1.2.

Source: https://www.khronos.org/opengl/wiki/Rendering_Pipeline_Overview

A vertex shader

A fragment shader

s

Pascal? ● ObjectWindows ++ ● Pointer arithmetic ++ ● Compiler ++ ● IDE ++ ● System library --

FreePascal ● Author terrified of leaving DOS. ● https://www.freepascal.org/ ● fpc -Mtp foo.pas ● fpc -Mtp -Ci -Co -CR -Cr -Ct -g foo.pas

Artistic license? DFSG??

A new GRAPHWIN.PAS ● “graphwin.pas”

Running it

Does it work?

Grab the code! It works! ● https://github.com/davel/perldemo ● https://github.com/davel/pascal-games ● My customer needs more Perl, talk to me.