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I have been playing with DSLs a little, here is the kind of syntax that I would choose: invoice "INV-001" for "ACME Corp" item "Hosting" 100 x 3 item

I have been playing with DSLs a little, here is the kind of syntax that I would choose: invoice "INV-001" for "ACME Corp" item "Hosting" 100 x 3 item "Support" 50 x 2 tax 20% invoice "INV-002" for "Globex" item "Consulting" 200 x 5 discount 10% tax 21% In contrast to XML (even with authoring tools), my feeling is that XML (or any angle-bracket language tbh) is just too hard to write correctly (ie XML syntax and XMl schema parsing is very unforgiving) and has a lot of noise when you read it that obscures the main intent of the DSL code.

librasteve 7mo ago
Here's how the built-in Raku Grammar can be used to parse this. I can see Raku generating the XML as the Actions from this Grammar so allow ease of DSL authoring with XML as a interchange and strict scheme validation format. grammar InvoiceDSL { token TOP { ^ <invoice>+ % \n* $ } token invoice { <header> \n <line>+ } token header { 'invoice' \h+ <id=string> \h+ 'for' \h+ <client=string> } token line { \h**4 <entry> \n? } token entry { | <item> | <tax> | <discount> } token item { 'item' \h+ <desc=string> \h+ <price=num> \h+ 'x' \h+ <qty=int> } token tax { 'tax' \h+ <percent=num> '%' } token discount { 'discount' \h+ <percent=num> '%' } token string { \" <( <-["]>* )> \" } token num { \d+ [ '.' \d+ ]? } token int { \d+ } }
retost 7mo ago
I have a preference for command/argument DSLs for certain things, such as the example given, over XML etc, for the reasons given. As an occasional Tcl coder, the example would actually be a valid Tcl script - after adding invoice, item, tax and discount procedures, the example could be run as a script. The procedures would perform actions as needed for the arguments. It's a shame that there isn't a common library that can be used for these types of tasks. Tcl evolved into something quite complex - compiling to bytecode, object oriented features, etc, etc. Although Tcl was originally intended to be embedded in apps, that boat sailed a long time ago (except for FPGA tools, which is where I use it).

librasteve 7mo ago

Here's how the built-in Raku Grammar can be used to parse this. I can see Raku generating the XML as the Actions from this Grammar so allow ease of DSL authoring with XML as a interchange and strict scheme validation format. grammar InvoiceDSL { token TOP { ^ <invoice>+ % \n* $ } token invoice { <header> \n <line>+ } token header { 'invoice' \h+ <id=string> \h+ 'for' \h+ <client=string> } token line { \h**4 <entry> \n? } token entry { | <item> | <tax> | <discount> } token item { 'item' \h+ <desc=string> \h+ <price=num> \h+ 'x' \h+ <qty=int> } token tax { 'tax' \h+ <percent=num> '%' } token discount { 'discount' \h+ <percent=num> '%' } token string { \" <( <-["]>* )> \" } token num { \d+ [ '.' \d+ ]? } token int { \d+ } }

retost 7mo ago

I have a preference for command/argument DSLs for certain things, such as the example given, over XML etc, for the reasons given. As an occasional Tcl coder, the example would actually be a valid Tcl script - after adding invoice, item, tax and discount procedures, the example could be run as a script. The procedures would perform actions as needed for the arguments. It's a shame that there isn't a common library that can be used for these types of tasks. Tcl evolved into something quite complex - compiling to bytecode, object oriented features, etc, etc. Although Tcl was originally intended to be embedded in apps, that boat sailed a long time ago (except for FPGA tools, which is where I use it).