Mark: 24 revision(s)

2008-11-03T05:20:28Z

24 revision(s)

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== Initial problems ==

*The error function was called before it was defined and hence needed a prototype declaration.
*"strcmpi" was misspelled as "strcimp"

== Task Two ==

mkNode('-',mkNode('-',mkNode('a',0),mkNode('b',0),0),0);

*Took a while to figure out how to use mkNode

http://studwww.cs.auckland.ac.nz/~hpan027/250-8-1.jpg

*Still can't get the converter to work internally. Had to convert the .dot file manually

== Task Three ==

mkNode('?',mkNode('>',mkNode('+',mkNode('a',0),mkNode('b',0),0),mkNode('c',0),0),mkNode('*',
mkNode('z',0),mkNode('+',mkNode('y',0),mkNode('b',0),0)),mkNode('?',mkNode('=',mkNode('a',0),
mkNode('2',0),0),mkNode('-',mkNode('x',0),mkNode('y',0),0),mkNode('-',mkNode('y',0),mkNode('x',0),0),0),0);

*Is it supposed to be this long?

== Task Four ==

*Cannot even begin to imagine what this would look like

http://studwww.cs.auckland.ac.nz/~hpan027/250-8-2.jpg

*Makes sense
*Horrible quality for some reason ('C', some '-' and some '=' not drawn properly)

== Task Five ==

*Possibly because it expects two set of statements to follow the '?'
*Not really sure at this point

== Task Six ==

*Initial impression: could take a while
*Draft code
int eval( ParseTree* pt ) {
//base case: if + - * /
//evalute number within brackets with the operator
//else eval( subtree )
}

*Very basic code working for single operation between two single-digit integers
int eval( ParseTree* pt ) {
//base case: if + - * /
if( pt->arity == 2 )
switch(pt->name){
case '+': return atoi(&pt->arg[0]->name)+atoi(&pt->arg[1]->name); break;
case '-': return atoi(&pt->arg[0]->name)-atoi(&pt->arg[1]->name); break;
case '*': return atoi(&pt->arg[0]->name)*atoi(&pt->arg[1]->name); break;
case '/': return atoi(&pt->arg[0]->name)/atoi(&pt->arg[1]->name); break;
}

//evalute number within brackets for with the operator
//else eval( subtree )
}

*This won't work for anything with one or three arguments
*Perhaps base case should be if it is a single integer leaf?
*Turned out to work fine
int eval( ParseTree* pt ) {
if( atoi(&pt->name) > 0 ) //base case integer leaf
return atoi(&pt->name);
else
switch(pt->name){
case '+': return eval(pt->arg[0])+eval(pt->arg[1]); break;
case '-': return eval(pt->arg[0])-eval(pt->arg[1]); break;
case '*': return eval(pt->arg[0])*eval(pt->arg[1]); break;
case '/': return eval(pt->arg[0])/eval(pt->arg[1]); break;
}
}
*However screwed for anything that isn't an operation with two numbers (e.g. -(1+2))
*Although single argument operations would only apply to "-" and "+" - i.e. *(2-3) or /(5) makes no sense
*Use if statements to catch single argument operations?

case '+': return ( pt->arity>1 ? eval(pt->arg[0])+eval(pt->arg[1]) : eval(pt->arg[0]) );
case '-': return ( pt->arity>1 ? eval(pt->arg[0])-eval(pt->arg[1]) : -1* eval(pt->arg[0]) );
*Seems to work
*Now need to consider 2+ arguments & if statements?
*If statement would probably be a separate case
*For 2+ argument possibly loop through the whole arg array for values
*Each case statement would probably look something like
case '+': int i=0; int value = 0; for( i = 0; i < pt->arity-1; i++ ) {
value+=eval(pt->arg[i]);
return value;

== After the lab ==

Comment on what?

Neat reports.

SE250:lab-8:hpan027 - Revision history

Mark: 24 revision(s)