cl-who-devel December 2011

cl-who-devel@common-lisp.net

7 participants
5 discussions

Re: [cl-who-devel] loop and with-html-output
by Tyler Smith 22 Dec '11

22 Dec '11

On Thu, Dec 22, 2011 at 1:38 PM, Ron Garret <ron(a)flownet.com> wrote: > > It's not a "special circumstance", it's what macros do. The S-expressions that are arguments to macros are passed verbatim (that is, without being evaluated) to the macro expander function for that macro. It gets confusing because one of the things that the macro expander can elect to do is to return that symbol as part of the macro expansion in a context where that symbol gets evaluated, so a symbol passed as an argument to a macro *might* become a variable reference, or it might not. > Ah, I see this now. Even within W-H-O, the same variable gets evaluated in some places: if I use a variable for an attribute value it gets evaluated, but but not when I use it as the tag body. This is clearly spelled out in the docs, I see now, but it took me a while to wrap my head around it. Thanks! Tyler

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Re: [cl-who-devel] loop and with-html-output
by Tyler Smith 22 Dec '11

22 Dec '11

On Thu, Dec 22, 2011 at 12:10 PM, Jeffrey Cunningham <jeffrey(a)jkcunningham.com> wrote: > On Thu, 22 Dec 2011 09:03:43 -0800, Tyler Smith > <tyler.smith(a)mail.mcgill.ca> wrote: > >> On Thu, Dec 22, 2011 at 10:53 AM, Sebastian Tennant >> <sebyte(a)smolny.plus.com> wrote: >>> http://weitz.de/cl-who/#syntax >>> >>> Hope this helps. >>> >> >> Not really, that's the documentation that I'm confused about. It >> starts out with the statement that strings will be printed verbatim. >> My variables are strings, but they aren't printed. I understand from >> Jens' response that I can get the function to work by wrapping my >> variables in (str ...), but I don't understand why that's necessary. >> The documentation of str suggests it's not necessary for strings: >> >> A form which is neither a string nor a keyword nor a list beginning >> with a keyword will be left as is except for the following >> substitutions: >> >> My variables are already strings: >> > > Your variables are variables (symbols bound to addresses pointing to > strings), not strings. > > --Jeff Oh, I see. Is this a special circumstance of the macro then, or are symbols bound to strings and actual strings not interchangeable in Lisp? Thanks for your patience, Tyler

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Re: [cl-who-devel] loop and with-html-output
by Tyler Smith 22 Dec '11

22 Dec '11

On Thu, Dec 22, 2011 at 12:30 PM, Edi Weitz <edi(a)agharta.de> wrote: > On Thu, Dec 22, 2011 at 6:19 PM, Tyler Smith <tyler.smith(a)mail.mcgill.ca> wrote: > >> Oh, I see. Is this a special circumstance of the macro then, or are >> symbols bound to strings and actual strings not interchangeable in >> Lisp? > > See my previous reply. > > There's nothing specific about Lisp here. The concept you'll want to > look up is "literal". > Ok, I think I have a general understanding. I have to spend some more time on macros and the distinction between run-time and compile time. Thanks for your help, Tyler

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Re: [cl-who-devel] loop and with-html-output
by Tyler Smith 22 Dec '11

22 Dec '11

On Thu, Dec 22, 2011 at 10:53 AM, Sebastian Tennant <sebyte(a)smolny.plus.com> wrote: > http://weitz.de/cl-who/#syntax > > Hope this helps. > Not really, that's the documentation that I'm confused about. It starts out with the statement that strings will be printed verbatim. My variables are strings, but they aren't printed. I understand from Jens' response that I can get the function to work by wrapping my variables in (str ...), but I don't understand why that's necessary. The documentation of str suggests it's not necessary for strings: A form which is neither a string nor a keyword nor a list beginning with a keyword will be left as is except for the following substitutions: My variables are already strings: * (multiple-value-bind (records fields) (select [genus] [species] :from "specimens" :where [< [specimen_id] 4]) (loop for rec in records do (loop for label in fields for val in rec do (fresh-line) (princ (stringp label)) (princ (stringp val))))) TT TT TT TT TT TT NIL * Can someone explain why my variables aren't being treated as strings within with-html-output? The definition of (str ...) continues: Forms that look like (str form1 form*) will be substituted with (let ((result form1)) (when result (princ result s))). I'm new to Lisp (as must be clear by now!): what is the difference between (princ form1) and (let ((result form1)) (princ result)) Thanks for your help, Tyler

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[cl-who-devel] loop and with-html-output
by Tyler Smith 22 Dec '11

22 Dec '11

Hi, I'm new to lisp in general, trying to get cl-sql and cl-who working together. I'm stumped in my efforts to generate a definition list from an sql query. The following works as expected: (multiple-value-bind (records fields) (select [genus] [species] :from "specimens" :where [= [collector] "Test"]) (loop for rec in records do (loop for label in fields for val in rec do (fresh-line) (print label) (print val)))) => "GENUS" "Scleria" "SPECIES" "triglomerata" However, swapping print for with-output-to-html fails: * (multiple-value-bind (records fields) (select [genus] [species] :from "specimens" :where [= [collector] "Test"]) (loop for rec in records do (loop for label in fields for val in rec do (fresh-line) (with-html-output (*standard-output* nil :indent nil) (:dt label) (:dd val))))) <dt></dt><dd></dd> <dt></dt><dd></dd> What have I missed? Any other suggestions for doing this in a lispier way would also be welcome. Thanks, Tyler

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cl-who-devel December 2011