path: root/src/interp/int-top.boot.pamphlet

\documentclass{article}
\usepackage{axiom}
\begin{document}
\title{\$SPAD/src/interp int-top.boot}
\author{The Axiom Team}
\maketitle
\begin{abstract}
\end{abstract}
\eject
\tableofcontents
\eject
\section{intloopReadConsole}

This is the top level loop when reading from the input console.  This
function calls itself after processing the current line.  Because of
this it is important that the underlying common lisp supports
tail-recursion.

Normally we never really exit this function.

We read a string from the input. The serverReadLine\cite{1} function
is a special readline function that handles communication with the 
session manager code, which is a separate process running in parallel.
In the usual case it just returns the current string.

If the user enters a blank line ([[#a=]]) then just put up another prompt
and then tail-recursively call [[intloopReadConsole]].

If the user has set [[$DALYMODE]] to true and the new line starts with
an open parenthesis then the input is assumed to be a lisp expression
and is evaluated by the underlying common lisp. This is useful if you
are doing a lot of debugging. Commands can also be executed in the
underlying common lisp by using the [[)lisp]] command. In either case we
tail-recursively call [[intloopReadConsole]].

If the user typed [[)fin]] then we exit the loop and drop into the
underlying common lisp. You can use the [[(restart)]] function call
to return to the top level loop.

If the input line starts with a close parenthesis we parse the 
input line as a command rather than an expression. We execute the command
and then tail-recursively call [[intloopReadConsole]].

If the input line contains a trailing underscore, which is the standard
end-of-line escape character, then we continue to read the line by
tail-recursively calling [[intloopReadConsole]].

If none of the above conditions occur we simply evaluate the input line
and then tail-recursively call [[intloopReadConsole]].

However, there was a small bug in the test for the system command
[[)fin]]. Originally, the test took the form:
\begin{verbatim}
   intloopPrefix?('")fin",a) => []
\end{verbatim}
This test was flawed in two ways. First, it would match {\sl any}
command beginning with [[)fin]]. Second, it would {\sl only} match
names beginning with [[)fin]], although [[)fi]] is an acceptable
abbreviation for this command. The improved test takes the form:
\begin{verbatim}
    pfx := stripSpaces intloopPrefix?('")fi",a)
    pfx and ((pfx = '")fi") or (pfx = '")fin")) => []
\end{verbatim}

\section{intloopPrefix?}
The [[intloopPrefix?(prefix, whole)]] function simply tests if the string
[[prefix]] is a prefix of the string [[whole]]. The original
implementation discounts {\sl any} whitespace in [[whole]] in deciding a
match, when a more sensible behavior would be to discount only leading
whitespace.

Moreover, the function SUBSTRING\cite{2} was being improperly called.
The reason why this improper call had gone undetected is that
generally [[intloopPrefix?]] is invoked with a prefix string of length
one -- hence the start position for the substring would generally
begin at index [[spaces]] (which is what we want).

The original code read:
\begin{verbatim}
intloopPrefix?(prefix,whole) ==
     #prefix > #whole => false
     good:=true
     spaces := 0
     i := 0
     len := #prefix
     wlen := #whole
     for j in 0.. while (good and i < len and j < wlen) repeat
       good:= (prefix.i = whole.j) or (whole.j = char " ")
       if prefix.i = whole.j then i := i+1
       if whole.j = char " " then spaces := spaces + 1
     spaces = wlen => nil
     if good then SUBSTRING(whole,#prefix+spaces-1,nil) else good

\end{verbatim}

The improved version of [[inloopPrefix?(prefix, whole)]] returns the
string [[whole]] sans leading whitespace if the match succeeds, else nil.

<<intloopPrefix?>>=
intloopPrefix?(prefix,whole) ==
     #prefix > #whole => false
     good := true
     leading := true
     spaces := 0
     i := 0
     len := #prefix
     wlen := #whole
     for j in 0.. while (good and i < len and j < wlen) repeat
       good := (prefix.i = whole.j) or (leading and (whole.j = char " "))
       if prefix.i = whole.j then i := i+1
       if (whole.j = char " ") and leading then 
         spaces := spaces + 1
       else leading := false
     spaces = wlen => nil
     if good then SUBSTRING(whole,spaces,nil) else good

@
\section{License}
<<license>>=
-- Copyright (c) 1991-2002, The Numerical ALgorithms Group Ltd.
-- All rights reserved.
--
-- Redistribution and use in source and binary forms, with or without
-- modification, are permitted provided that the following conditions are
-- met:
--
--     - Redistributions of source code must retain the above copyright
--       notice, this list of conditions and the following disclaimer.
--
--     - Redistributions in binary form must reproduce the above copyright
--       notice, this list of conditions and the following disclaimer in
--       the documentation and/or other materials provided with the
--       distribution.
--
--     - Neither the name of The Numerical ALgorithms Group Ltd. nor the
--       names of its contributors may be used to endorse or promote products
--       derived from this software without specific prior written permission.
--
-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
-- IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
-- TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
-- PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
-- OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
-- EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-- PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
-- PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
-- LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
-- NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
-- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

@
<<*>>=
<<license>>

)package "BOOT"

--% INTERPRETER TOP LEVEL

spad() ==
  -- starts the interpreter but does not read in profiles, etc.
  $PrintCompilerMessageIfTrue: local
  $inLispVM : local := nil
  setOutputAlgebra "%initialize%"
  runspad()
  'EndOfSpad

runspad() ==
  mode:='restart
  while mode='restart repeat
    resetStackLimits()
    CATCH($quitTag, CATCH('coerceFailure,
                  mode:=CATCH('top__level, ncTopLevel())))

ncTopLevel() ==
-- Top-level read-parse-eval-print loop for the interpreter.  Uses
-- the Bill Burge's parser.
  IN_-STREAM: fluid := CURINSTREAM
  _*EOF_*: fluid := NIL
  $InteractiveMode :fluid := true
  $BOOT: fluid := NIL
  $NEWSPAD: fluid := true
  $SPAD: fluid := true
  $e:fluid := $InteractiveFrame
  ncIntLoop()


ncIntLoop() ==
  CURINSTREAM : local := _*STANDARD_-OUTPUT_*
  CUROUTSTREAM : local := _*STANDARD_-INPUT_*
  intloop()


intloop () ==
    mode := $intRestart
    while mode = $intRestart repeat
      resetStackLimits()
      mode := CATCH($intTopLevel,
                    SpadInterpretStream(1, ["TIM", "DALY", "?"], true))


SpadInterpretStream(str, source, interactive?) ==
    $fn              : local := source
    pile?                    := not interactive?
    $libQuiet        : local := not interactive?
    $newcompMode     : local := false
--  following seems useless and causes ccl package problems
--    $InteractiveMode : local := false
 
    $newcompErrorCount: local := 0 -- SMW Feb 2/90.
                                   -- Used in highComplete, ncHardError etc.
 
    $okToExecuteMachineCode: local := true -- set false on error
    $inclAssertions: local := ["AIX", "CommonLisp"] -- Jan 28/90
 
 
    $lastPos               : local := $nopos   ------------>!!!
    $erMsgToss             : local := false --------------->!!!
    $ncMsgList             : local := nil
 
    $systemCommandFunction : local := function InterpExecuteSpadSystemCommand
    $shoeReadLineFunction  : local := function serverReadLine
    $promptMsg             : local := 'S2CTP023
 
    interactive? =>
                PRINC(MKPROMPT())
                intloopReadConsole('"", str)
                []
    intloopInclude (source,0)
    []
 
    -----------------------------------------------------------------

intloopReadConsole(b, n)==
    a:= serverReadLine(_*STANDARD_-INPUT_*)
    not STRINGP a => leaveScratchpad()
    #a=0 =>
             PRINC(MKPROMPT())
             intloopReadConsole('"", n)
    $DALYMODE and intloopPrefix?('"(",a) =>
            intnplisp(a)
            PRINC(MKPROMPT())
            intloopReadConsole('"",n)
    pfx := stripSpaces intloopPrefix?('")fi",a)
    pfx and ((pfx = '")fi") or (pfx = '")fin")) => []
    b = '"" and (d := intloopPrefix?('")", a)) =>
             setCurrentLine d
             c := ncloopCommand(d,n)
             PRINC(MKPROMPT())
             intloopReadConsole('"", c)
    a:=CONCAT(b,a)
    ncloopEscaped a => intloopReadConsole(SUBSEQ(a, 0, (LENGTH a) - 1),n)
    c := intloopProcessString(a, n)
    PRINC(MKPROMPT())
    intloopReadConsole('"", c)
 
<<intloopPrefix?>> 
 
intloopProcess(n,interactive,s)==
     StreamNull s => n
     [lines,ptree]:=CAR s
     pfAbSynOp?(ptree,"command")=>
            if interactive then setCurrentLine tokPart ptree
            FUNCALL($systemCommandFunction, tokPart ptree)
            intloopProcess(n ,interactive ,CDR s)
     intloopProcess(intloopSpadProcess(n,lines,ptree,interactive)
                 ,interactive ,CDR s)
 
intloopEchoParse s==
         [dq,stream]:=CAR s
         [lines,rest]:=ncloopDQlines(dq,$lines)
         setCurrentLine(mkLineList(lines))
         if $EchoLines then ncloopPrintLines lines
         $lines:=rest
         cons([[lines,npParse dqToList dq]],CDR s)
 
intloopInclude0(st, name, n) ==
    $lines:local:=incStream(st,name)
    intloopProcess(n,false,
      next(function intloopEchoParse,
        next(function insertpile,
          next(function lineoftoks,$lines))))
 
intloopInclude1(name,n) ==
          a:=ncloopIncFileName name
          a => intloopInclude(a,n)
          n
 
intloopProcessString(s,n) ==
     setCurrentLine s
     intloopProcess(n,true,
         next(function ncloopParse,
           next(function lineoftoks,incString s)))
 
$pfMacros := []

intloopSpadProcess(stepNo,lines,ptree,interactive?)==
    $stepNo:local := stepNo
    $currentCarrier := cc := ['carrier]
    ncPutQ(cc, 'stepNumber, stepNo)
    ncPutQ(cc, 'messages, $ncMsgList)
    ncPutQ(cc, 'lines, lines)
    $ncMsgList := nil
    result := CatchAsCan(flung, Catch("SpadCompileItem",
     CATCH($intCoerceFailure, CATCH($intSpadReader,
       interp(cc, ptree, interactive?))))) where
 
        interp(cc, ptree, interactive?) ==
            ncConversationPhase(function phParse,            [cc, ptree])
            ncConversationPhase(function phMacro,            [cc])
            ncConversationPhase(function phIntReportMsgs,[cc, interactive?])
            ncConversationPhase(function phInterpret,        [cc])
 
            #ncEltQ(cc, 'messages) ^= 0 => ncError()
 
    intSetNeedToSignalSessionManager()
    $prevCarrier := $currentCarrier
    result = 'ncEnd     => stepNo
    result = 'ncError   => stepNo
    result = 'ncEndItem => stepNo
    stepNo+1
 
phInterpret carrier ==
  ptree := ncEltQ(carrier, 'ptree)
  val := intInterpretPform(ptree)
  ncPutQ(carrier, 'value, val)
 
 
--% phReportMsgs: carrier[lines,messages,..]-> carrier[lines,messages,..]
phIntReportMsgs(carrier, interactive?) ==
    $erMsgToss => 'OK
    lines := ncEltQ(carrier, 'lines)
    msgs  := ncEltQ(carrier, 'messages)
    nerr  := #msgs
    ncPutQ(carrier, 'ok?, nerr = 0)
    nerr = 0 => 'OK
    processMsgList(msgs, lines)
    intSayKeyedMsg ('S2CTP010,[nerr])
    'OK
 
mkLineList lines ==
  l := [CDR line for line in lines | nonBlank CDR line]
  #l = 1 => CAR l
  l

nonBlank str ==
  value := false
  for i in 0..MAXINDEX str repeat
    str.i ^= char " " =>
      value := true
      return value
  value
      
ncloopCommand (line,n) ==
         a:=ncloopPrefix?('")include",line)=>
                  ncloopInclude1( a,n)
         FUNCALL($systemCommandFunction,line)
         n

ncloopEscaped x==
     esc :=false
     done:=false
     for i in (# x) - 1 .. 0 by -1 while not done repeat
         done:=
              x.i='" ".0 =>false
              x.i='"__".0=>
                       esc:=true
                       true
              true
     esc

ncloopDQlines (dq,stream)==
        StreamNull stream
        a:= poGlobalLinePosn tokPosn CADR dq
        b:= poGlobalLinePosn CAAR stream
        streamChop (a-b+1,stream)
 
streamChop(n,s)==
    if StreamNull s
    then [nil,nil]
    else if EQL(n,0)
         then [nil,s]
         else
            [a,b]:= streamChop(n-1,cdr s)
            line:=car s
            c:=ncloopPrefix?('")command",CDR line)
            d:= cons(car line,if c then c else cdr line)
            [cons(d,a),b]
 
ncloopPrintLines lines ==
        for line in lines repeat WRITE_-LINE CDR line
        WRITE_-LINE '" "
 
ncloopIncFileName string==
                fn := incFileName string
                not fn =>
                    WRITE_-LINE (CONCAT(string, '" not found"))
                    []
                fn

ncloopParse s==
         [dq,stream]:=CAR s
         [lines,rest]:=ncloopDQlines(dq,stream)
         cons([[lines,npParse dqToList dq]],CDR s)
 
ncloopInclude0(st, name, n) ==
     $lines:local := incStream(st, name)
     ncloopProcess(n,false,
         next(function ncloopEchoParse,
           next(function insertpile,
            next(function lineoftoks,$lines))))
 
ncloopInclude1(name,n) ==
          a:=ncloopIncFileName name
          a => ncloopInclude(a,n)
          n

incString s== incRenumber incLude(0,[s],0,['"strings"] ,[Top])

ncError() ==
    THROW("SpadCompileItem",'ncError)

--% Compilation Carriers
--  This data structure is used to carry information between phases.

--% phParse: carrier[tokens,...] -> carrier[ptree, tokens,...]
--)line (defun pretty (x) (boottran::reallyprettyprint x))
--)line (defun packagetran (x) (boot::|packageTran|))
phParse(carrier,ptree) ==
    phBegin 'Parsing
    if $ncmParse then
           nothing
           intSayKeyedMsg ('S2CTP003,[%pform ptree])
    ncPutQ(carrier, 'ptree, ptree)
    'OK
 

--% phMacro: carrier[ptree,...] -> carrier[ptree, ptreePremacro,...]
phMacro carrier ==
    phBegin 'Macroing
    ptree  := ncEltQ(carrier, 'ptree)
    ncPutQ(carrier, 'ptreePremacro, ptree)
 
    ptree  := macroExpanded ptree
    if $ncmMacro then
        intSayKeyedMsg ('S2CTP007,[%pform ptree] )
 
    ncPutQ(carrier, 'ptree, ptree)
    'OK
 
--% phReportMsgs: carrier[lines,messages,..]-> carrier[lines,messages,..]
phReportMsgs(carrier, interactive?) ==
    $erMsgToss => 'OK
    lines := ncEltQ(carrier, 'lines)
    msgs  := ncEltQ(carrier, 'messages)
    nerr  := #msgs
    ncPutQ(carrier, 'ok?, nerr = 0)
    interactive? and nerr = 0 => 'OK
    processMsgList(msgs, lines)
    intSayKeyedMsg ('S2CTP010,[nerr])
    'OK
 
ncConversationPhase(fn, args) ==
    carrier := first args
 
    $ncMsgList: local := []
    $convPhase: local := 'NoPhase
 
    UNWIND_-PROTECT( APPLY(fn, args), wrapup(carrier) ) where
        wrapup(carrier) ==
            for m in $ncMsgList repeat
                ncPutQ(carrier, 'messages, [m, :ncEltQ(carrier, 'messages)])
 
ncloopPrefix?(prefix,whole) ==
     #prefix > #whole => false
     good:=true
     for i in 0..#prefix-1 for j in 0.. while good repeat
                good:= prefix.i = whole.j
     if good then SUBSTRING(whole,#prefix,nil) else good
 
phBegin id ==
    $convPhase := id
    if $ncmPhase then intSayKeyedMsg('S2CTP021,[id])
 
PullAndExecuteSpadSystemCommand stream ==
    ExecuteSpadSystemCommand CAR stream
    CDR stream

ExecuteSpadSystemCommand string ==
  FUNCALL($systemCommandFunction, string)

@
\eject
\begin{thebibliography}{99}
\bibitem{1} [[src/interp/server.boot.pamphlet]]
\bibitem{2} [[src/interp/vmlisp.lisp.pamphlet]]
\end{thebibliography}
\end{document}