Gambit-list Août 2005

gambit-list@iro.umontreal.ca

12 participants
35 discussions

Strange echo in pseudo-terminals on MacOSX10.4 Gambit-Cb14
by Francois Magnan 09 Aoû '05

09 Aoû '05

Hi, Me again... I just separated my questions to different threads... There is strange echo I get by communicating with a pseudo terminal process on MacOSX 10.4 Gambit-Cb14. I open a dummy process that is a pseudo-terminal using the open- process command and when I send data to the port that data gets repeated in the pseudo-terminal output-port. See the example below for better clarity. Can I turn off that echo? I cannot test it on the WinXP platform since open-process is not implemented for (MinGW or Cygwin). Thank you, Francois Magnan --------------------- ; Pseudo-terminal program (define (command-loop) (let ((command (read-line))) (serve-command command) (command-loop))) (define (serve-command command) (pp (list "got command" command))) (command-loop) ; build the above to an executable file called "/tmp/pttest" using gsc and gcc. --------------------- (define (test-pseudo-terminal) (let ((port (open-process (list path: "/tmp/pttest" stderr-redirection: #t pseudo-terminal: #t )))) ;(force-output port) (pp port) (force-output) (thread-sleep! 1) (display "toto\n" port) (force-output port) (pp (read-line port)) (pp (read-line port)) (close-port port))) (test-pseudo-terminal) ; execute the above in a gsi interpreter ; On MacOSX 10.4 I get ; "\33[1mtoto\33[m" ;"(\"got command\" \"toto\")"

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file-exists? on
by Francois Magnan 08 Aoû '05

08 Aoû '05

Hi, On WindowsXP (MinGW) the promitive file-exists? seems to be broken in Gambit-Cb14... Is anybody experiencing the same problem? Thank you, Francois Magnan (file-exists? "/bin/ls") ; Works on MacOSX 10.4 (file-exists? "C:/Decads/bin/decads.exe") ; Fails on Windows XP (MinGW) although that file exists on my machine.

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(begin) mini-issue
by Christian 07 Aoû '05

07 Aoû '05

Hello I've noticed some time ago that (begin) is the best thing a macro can return if it doesn't want to insert any code. Like: (define-macro (STRIP . x) '(begin)) or (define-macro (toggle-foo-at-compile-time) (set! foo (not foo)) '(begin)) It's better than returning #f or #!void since (begin) even works when being put before internal definitions or declarations at the start of a function, like: (define (bar x) (toggle-foo-at-compile-time) (define a 5) ...) Encouraged by this, I hoped that it would also work in tail position, e.g. just disappear and not disturb delivery of the return value. Like: (define (baz x) (toggle-foo-at-compile-time) (+ baz 5) (toggle-foo-at-compile-time)) But this is giving a compilation error, "Ill-formed special form: begin". Simpler test cases: ; this is the only case which doesn't give a compile-/expansion time error: ; (but it won't display "one" in the repl, just as it would return #!void) (begin "one" (begin)) ;(display (begin "two" (begin))) ; ^- Ill-formed special form: begin ;(pp (lambda() (begin "three" (begin)))) ; ^- Ill-formed special form: begin ; this works, of course, printing "FOUR". (pp (begin "three" (begin "FOUR"))) The same happens in the interpreter and the compiler. (This is on gambc40b14 on Debian x86.) This construct could be useful in some (rare) cases (see my following mail on macro-debugging). R5RS doesn't seem to say anything on this. Scheme48 and Mzscheme act the same in all cases. Gauche and SCM don't complain but just always return #<undef> / #<unspecified> from such a construct. bigloo -i only complains in the lambda creation case, otherwise it returns #unspecified. Thanks, Christian.

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macro debugging
by Christian 07 Aoû '05

07 Aoû '05

Hello For some reason, errors in macro expansion don't trigger the debugger. This may be on purpose, but it makes macro debugging difficult. Gladly, I've found a workaround: run (current-exception-handler primordial-exception-handler) before expansion of the faulty macro, or (with-exception-handler primordial-exception-handler (eval '(code-containing-calls-to-faulty-macro))) but using eval disconnects the code from the lexical environment. Now I'm looking for a simpler way to turn macro debugging on. I've thought about a macro; since using eval is out of question (because of breaking lexical env), I wanted to work around this by saving and restoring the current handler manually: (define-macro (cj-env#insert-result-of expr) (eval expr)) (define-macro (with-macro-debugging body) `(begin (cj-env#insert-result-of (begin (define | saved-exception-handler| (current-exception-handler)) (warn "saved:" | saved-exception-handler|) (current-exception-handler primordial-exception-handler) (warn "now is:" (current-exception-handler)) '(begin))) ,body (cj-env#insert-result-of (begin (warn "put back:" | saved-exception-handler|) (current-exception-handler | saved-exception-handler|) (warn "now is:" (current-exception-handler)) '(begin)))))) But this won't work because the macro call after ,body isn't allowed, see my former mail about (begin). What are your suggestions? Cheers Christian.

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path-strip-directory bug?
by Christian 07 Aoû '05

07 Aoû '05

Hello I guess the latter of those is not correct: > (path-strip-directory "//2") "2" > (path-strip-directory "/2") "/2" This is on gambc40b14 on Debian ppc. thanks, Christian.

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Gambit-list Août 2005