[Coco] The Coco's first webserver, written in Basic09

[Christian Lesage]

I don't understand where you are heading to with this. You would need 
more than an expression evaluator in order to program a server that can 
generate dynamic content. In JavaScript, for instance, the eval() 
function parses the string it is given as a parameter, looking for 
JavaScript code. If it finds any JavaScript code, it will be executed. 
If you want to simulate the same behaviour in BASIC09, you will end up 
writing a complete BASIC09 interpreter on top of the underlying one, 
unless you find a way to inject an arbitrary string in the latter.

Hint: Use RUN.



Wayne Campbell wrote:

> OK. I did a little. I really don't know what I'm doing here, but this 

> is what I got for a start. There are many problems. First, Basic09's 

> precedence ordering acts on the expression as follows:

>

> 2*3+5/2

>

> is evaluated as

>

> 2*3/2+5, yielding a result of 8

>

> To get the result of 5 (what we're looking for), it would have to be 

> written as

>

> (2*3+5)/2 (the remainder of 1 is dropped)

>

> Because I am parsing the string "as I go", I am getting incorrect 

> results. Not just 8 iunstead of 5, I am getting wierd numbers. It also 

> does not account for numbers greater than 1 digit in length. Hopefully 

> someone else can make the necessary corrections/modifications. I 

> simply don't understand enough to do it right.

>

> Wayne

>

> PROCEDURE eval

> DIM a,b,c,d,e,f:INTEGER

> DIM mul,div,add,sub:BOOLEAN

> DIM inputStr:STRING

> a:=0 \b:=0 \c:=0 \d:=0 \e:=0 \f:=0

> mul:=FALSE \div:=FALSE \add:=FALSE \sub:=FALSE

> inputStr:="2*3+5/2"

> REM a:=(2*3+5)/2

> FOR b:=1 TO LEN(inputStr)

>  IF MID$(inputStr,b,1)>="0" AND MID$(inputStr,b,1)<="9" THEN

>    IF c=0 THEN

>      c:=VAL(MID$(inputStr,b,1))

>    ELSE IF d=0 THEN

>      d:=VAL(MID$(inputStr,b,1))

>      GOSUB 10

>    ELSE IF e=0 THEN

>      e:=VAL(MID$(inputStr,b,1))

>      GOSUB 10

>    ELSE IF f=0 THEN

>      f:=VAL(MID$(inputStr,b,1))

>      GOSUB 10

>    ENDIF \ENDIF \ENDIF \ENDIF

>  ELSE

>    IF MID$(inputStr,b,1)="*" THEN

>      mul:=TRUE

>    ELSE IF MID$(inputStr,b,1)="/" THEN

>      div:=TRUE

>    ELSE IF MID$(inputStr,b,1)="+" THEN

>      add:=TRUE

>    ELSE IF MID$(inputStr,b,1)="-" THEN

>      sub:=TRUE

>    ENDIF \ENDIF \ENDIF \ENDIF

>  ENDIF

> NEXT b

> PRINT a

> END

> 10 IF mul THEN

>  a:=a+c*d

>  mul:=FALSE

> ELSE IF div THEN

>  a:=a/e

>  div:=FALSE

> ELSE IF add THEN

>  a:=a+f

>  add:=FALSE

> ENDIF \ENDIF \ENDIF

> RETURN

>

> ----- Original Message ----- From: "Christian Lesage" 

> <hyperfrog at gmail.com>

> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>

> Sent: Wednesday, December 30, 2009 7:44 AM

> Subject: Re: [Coco] The Coco's first webserver, written in Basic09

>

>

>> If BASIC09 has an EVAL statement (I can't remember), you could easily 

>> program an ASP-like server. That would be pretty cool. I did that 

>> using another BASIC-like language a few years ago. I started from 

>> scratch, and the server was small, but good enough for small projects.

>>

>> Christian

>>

>>

>> -- 

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>> Coco at maltedmedia.com

>> http://five.pairlist.net/mailman/listinfo/coco 

>

>

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