Computer Science Canada

Syntax Typo?
Author:  chrispminis [ Tue Mar 14, 2006 2:48 pm ]
Post subject:  Syntax Typo?
Yeah, this isn't a big problem. I've just been staring at my code for about 40 minutes, and I still haven't found the problem. There are 2 errors. One is for a string literal that should end the line, the other is a syntax error expecting then.


code:
%Text Calculator
%by : Chris Pan
%Evaluates expressions by reading and interpreting strings
%Don't Steal

%Variables
var stringy : string
var number : real := 0
var mark, negmark : int
var string1, string2 : string
var dec, neg : boolean := false
var maxsymbol : int := 10
type prioritize :
    record
        svalue : string
        smark : int
        spriority : int
        sused : boolean
    end record
var symbol : array 1 .. maxsymbol of prioritize

for i : 1 .. maxsymbol
    symbol (i).svalue := " "
    symbol (i).smark := 0
    symbol (i).spriority := 0
    symbol (i).sused := false
end for

%Functions
function stringreal (str : string) : real
    mark := index (str, ".")
    negmark := index (str, "-")
    if mark > 0 then
        dec := true
    end if
    if negmark > 0 then
        neg := true
    end if

    for i : 1 .. length (str)
        if str (i) >= "1" and str (i) <= "9" then
            number *= 10
            number += (ord (str (i)) - 48)
        end if
    end for

    if dec = true then
        number := number / (10 ** (length (str) - mark))
    end if
    if neg = true then
        number := -number
    end if

    result number
end stringreal

function add (num1, num2 : real) : real
    result num1 + num2
end add

function subtract (num1, num2 : real) : real
    result num1 - num2
end subtract

function multiply (num1, num2 : real) : real
    result num1 * num2
end multiply

function divide (num1, num2 : real) : real
    result num1 / num2
end divide

function power (num1, num2 : real) : real
    result num1 ** num2
end power

function squareroot (num1 : real) : real
    result sqrt (num1)
end squareroot

function estimate (num1 : real) : int
    result round (num1)
end estimate

function up (num1 : real) : int
    result ceil (num1)
end up

function down (num1 : real) : int
    result floor (num1)
end down

%Main
%Input
get stringy : *

%Identify and Prioritize
for i : 1 .. length (stringy)
    if stringy (i) not= " " and stringy (i) < "0" or stringy (i) > "9" then
        symbol (i).sused := true
        symbol (i).svalue := stringy (i)
        symbol (i).smark := i
    end if
end for

for i : 1 .. length (stringy)
    if symbol (i).sused = true then
        if symbol (i).svalue = "q" or symbol (i).svalue = "h" then
            symbol (i).spriority := 7
        elsif symbol (i).svalue = "=" then
            symbol (i).spriority := 6
        elsif symbol (i).svalue = "~" or symbol (i).svalue = "<" or symbol (i).svalue = ">" then
            symbol (i).spriority := 5
        elsif symbol (i).svalue = "+" or symbol (i).svalue = "-" then
            symbol (i).spriority := 4
        elsif symbol (i).svalue = "x" or symbol (i).svalue = "X" or symbol (i).svalue = "*" or symbol (i).svalue = "/" then
            symbol (i).spriority := 3
        elsif symbol (i).svalue = "^" or symbol (i).svalue = "&" then
            symbol (i).spriority := 2
        elsif symbol (i).svalue = "(" then
            symbol (i).spriority := 1
        end if
    end if
end for

%Test Output
for i : 1 .. length (stringy)
    if symbol (i).sused then
        put symbol (i).svalue
        put symbol (i).smark
        put symbol (i).spriority
    end if
end for


Here's my code, I was just testing my prioritizing, for BEDMAS. I am sure the error is linked to an extra " somewhere but I can't find it! Please help.
Author:  Delos [ Tue Mar 14, 2006 3:27 pm ]
Post subject: 
code:

   elsif symbol (i).svalue = "\^" or symbol (i).svalue = "&" then


Not sure if it achieves what you want it to though...
Author:  chrispminis [ Tue Mar 14, 2006 3:33 pm ]
Post subject: 
I'm not sure what you are trying to point me towards. But where did the "\^" come from?

Im trying to prioritize them, "&" is my chosen square root sign. So exponents and square root go to the same priority level.
Author:  pavol [ Tue Mar 14, 2006 4:48 pm ]
Post subject: 
im not sure, you have more knowledge in this matter than i do, but if you take ^ out of:
code:
elsif symbol (i).svalue = "^" or symbol (i).svalue = "&" then
    symbol (i).spriority := 2

to make it:
code:
elsif symbol (i).svalue = "" or symbol (i).svalue = "&" then
    symbol (i).spriority := 2

i know it probably doesn't make your program do what you want, but what i'm trying to point out is that maybe "^" is the problem and maybe it is some kind of thing held special by Turing and you're not really allowed using it.
hope it gives some insight into your problem Smile
Author:  Delos [ Tue Mar 14, 2006 4:55 pm ]
Post subject: 
pavol is on the right track. '^' is a 'special thing' in Turing, but you are allowed to use it, provided you know how. In this case, if you wish to use it in a string, you need to provide the escape character '\' first. This is similar to using things like '\n' or '\"'.
I'm guessing the '^' would be for an exponent...
Author:  MysticVegeta [ Tue Mar 14, 2006 6:42 pm ]
Post subject: 
no ** is for exponent. ^ is reserved for other string purpose, and yes you would need to put "\" before the ^ so it would be "\^", its the same as saying "^", its for the same reason as for in java when you have to put "\\+" due to regex issues.
Author:  Delos [ Tue Mar 14, 2006 8:46 pm ]
Post subject: 
MysticVegeta wrote:
no ** is for exponent. ^ is reserved for other string purpose, and yes you would need to put "\" before the ^ so it would be "\^", its the same as saying "^", its for the same reason as for in java when you have to put "\\+" due to regex issues.


I meant in his proggie. You know, typing in "4^3" meaning four raised to the third power...
Author:  chrispminis [ Wed Mar 15, 2006 2:16 pm ]
Post subject: 
well, Ill try that, that makes sense. And Delos it is ** for exponent. Turing doesn't evaluate 2^3 = 8. Just another thing. If you wanted the backslash character (\) in a string would it be "\\"?
Author:  [Gandalf] [ Wed Mar 15, 2006 4:39 pm ]
Post subject: 
^ is the more 'universal' exponent representation, while ** is what Turing uses since ^ is reserved for other things.

Yes, to output a backslash you would use escape + \, or else "\\".
Author:  Clayton [ Wed Mar 15, 2006 4:57 pm ]
Post subject: 
i have to ask what do you mean by using backslash as an escape character? what is an escape character and what are they used for? i know this is off topic but i didnt want to start another thread just for this
Author:  Delos [ Wed Mar 15, 2006 10:50 pm ]
Post subject: 
Well, the most practical interpretation would be that you 'escape' from the literal string that you're using, and can implement a secondary command instead. So, for instance, you have "Hello /n World", which prints Hello and World on seperate lines. Since it's all in one string, the '/' allows you to drop out from the usual translation and actually do some manipulations.
This is rather limited though, since any more graphically-oriented procedures (Font. etc) don't support this (seeing as they create pictures). And of course, everyone loves pictures.
Wink

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