4 Function Calculator

I just coded this as I needed a simple calculator function for one of my scripts and thought it may be useful to others, as a search turned up only dedicated calculator scripts such as zxcalc, YAC and VeryCalc.

It may also be a good tool to let new scripters see some of the power of lists.

If anyone has ideas of how to optimise it, please post, as it was a quick copout to walk the whole list 4 times to set precedence and others may have a more efficient method.
For shot calculations though it should be fast enougth.

integer PubCh = 8; //set the listen channel here

float calc(string args)
{
	integer x; integer y; list l;
	y = llGetListLength(l = llParseString2List(args,[" "],["+","-","*","/"]));
	for(x=0;x<y;x++){if("/"==llList2String(l,x))l=llListReplaceList(l,[llList2Float(l,x-1)/llList2Float(l,x+1)],x-1,x+1);}
	for(x=0;x<y;x++){if("*"==llList2String(l,x))l=llListReplaceList(l,[llList2Float(l,x-1)*llList2Float(l,x+1)],x-1,x+1);}
	for(x=0;x<y;x++){if("-"==llList2String(l,x))l=llListReplaceList(l,[llList2Float(l,x - 1)-llList2Float(l,x + 1)],x - 1,x + 1);}
	for(x=0;x<y;x++){if("+"==llList2String(l,x))l=llListReplaceList(l,[llList2Float(l,x - 1)+llList2Float(l,x + 1)],x - 1,x + 1);}
	return llList2Float(l,0);
}

default
{
	state_entry()
	{
		llListen(PubCh,"","","");
	}
	listen(integer InpCh, string usr, key uid, string msg)
	{
		llOwnerSay((string)calc(msg));
	}
}

Is there a reason this has no formatting at all? It's never scripter-friendly
Anyway, right off there is one optimisation, which is to reduce the number of loops to two since multiplications and divisions have higher precedence than plus and minus, but it doesn't really matter what order they're done in.

iirc there's a way to do it in a single loop by parsing the string of characters, lets you account for negative numbers etc. too but I can't remember atm how you'd do it.

integer PubCh = 9; //set the listen channel here

float calc (string args) {
    integer x;
    list l = llParseString2List(args, [" "], ["+","-","*","/"]);
    integer y = l != []; 

    for(x = 0; x < y; x++) {
        if ("*" ==llList2String(l, x)) 
            l = llListReplaceList(
                l,
                [llList2Float(l, x - 1) * llList2Float(l, x + 1)],
                x - 1,
                x + 1
            );
        else if ("/" == llList2String(l, x)) 
            l = llListReplaceList(
                l,
                [llList2Float(l, x - 1) / llList2Float(l, x + 1)],
                x - 1,
                x + 1
            );
    }

    for (x = 0; x < y; x++) {
        if("+" == llList2String(l, x))
            l = llListReplaceList(
                l,
                [llList2Float(l, x - 1) + llList2Float(l, x + 1)],
                x - 1,
                x + 1
            );
        else if ("-" == llList2String(l, x)) 
            l = llListReplaceList(
                l,
                [llList2Float(l, x - 1) - llList2Float(l, x + 1)],
                x - 1,
                x + 1
            );
    }

    return llList2Float(l, 0);
}

default {
    state_entry() {
        llListen(PubCh, "", llGetOwner(), "");
    }

    listen(integer InpCh, string usr, key uid, string msg) {
        llResetTime();
        llOwnerSay((string)calc(msg));
        llOwnerSay((string)llGetTime() + " seconds");
    }
}

[

True It was part of a much larger script, so I tend to minimise white space and number of lines taken once a function is tested, just so that it takes minimum screen space whilst I’m working on the next function. I should have expanded it out again to post, especially as I thought it may help understand lists. I will remember next time I hope.

Thanks, that’s a 50% efficiency increase in one pass and I love your function to get the list length, haven’t seen that one before, I must remember it.