Began a new project: an resistance calculator.

It takes in user input in the form of an arithmetic state, with the addition of a new operation, Parallel => '//'. (stuff1)//(stuff2) returns 1/((1/stuff1)+(1/stuff2)). The operator takes precedence over addition/subtraction, but not multiplication/division. I.e., instead of BEDMAS (brackets, exponents, division, multiplication, addition, subtraction), it is now BEDMPAS (brackets,...multiplication, parallel, add...).

parseResistance.m

@@ -0,0 +1,104 @@
+function equivalentResistance = parseResistance( varargin )
+%PARSERESISTANCE takes in a string and computes the equivalent resistance
+%of the string notation for a circuit. E.g. (R1 + R2)//R3 means R1 in
+%series with R2, all parallel to R3.
+
+if(isempty(varargin))
+    inputString = input('Enter the circuit resistance layout:', 's');
+    equivalentResistance = parseBrackets(inputString);
+else
+    inputString = varargin{1};
+    equivalentResistance = parseBrackets(inputString);
+end
+
+end
+
+% Parses a bracket statement (expression with or without brackets)
+function result = parseBrackets( inputString )
+
+    bracketIndices = strfind(inputString, '(');
+
+    % If there are brackets, recursively evaluate
+    while(~isempty(bracketIndices))
+
+        openBracket = 0;
+        startIndex = bracketIndices(1);
+
+        for(i = startIndex:length(inputString))
+            if(inputString(i) == '(')
+                openBracket = openBracket + 1;
+            end
+
+            if(inputString(i) == ')')
+                openBracket = openBracket - 1;
+            end
+
+            if openBracket == 0
+                endIndex = i;
+                subString = inputString(startIndex+1:endIndex-1);
+
+                break;
+            end
+        end
+
+        newString = strrep(inputString, inputString(startIndex:endIndex), ...
+            num2str(parseBrackets(subString)));
+
+        disp(['Solving... ' inputString ...
+                    ' = ' newString]);
+
+        inputString = newString;
+
+        bracketIndices = strfind(inputString, '(');
+    end
+
+    %If no brackets in inputString left, evaluate Sum statements
+    result = parseSum(inputString);
+
+end
+
+% Parses a Sum statement, where Sum::=Parallel([+-]Parallel)*
+function result = parseSum( inputString )
+    nodes = regexp(inputString, '[+-]', 'split');
+
+%     %If no addition statements, return the evaluated Parallel expression.
+%     if(length(nodes) == 1)
+%         result = inputString;
+%         return;
+%     end
+
+    for node = nodes
+        subString = node{1};
+
+        inputString = strrep(inputString, subString, ...
+            num2str(parseParallel(subString)));
+    end
+
+    result = eval(inputString);
+
+end
+
+% Parses a Parallel statement, where Parallel::=Product(//Product)*
+function result = parseParallel( inputString )
+    nodes = regexp(inputString, '\/\/', 'split');
+
+%     %If no addition statements, return the evaluated Parallel expression.
+%     if(length(nodes) == 1)
+%         result = parseProduct(inputString);
+%         return;
+%     end
+%     
+    sum = 0;
+
+    for node = nodes
+        subString = node{1};
+        sum = sum + 1/(parseProduct(subString));
+    end
+
+    result = 1/sum;
+end
+
+% Parses a Product statement, where Product::=Number([\*\/]Number)*
+function result = parseProduct( inputString )
+    result = eval(inputString);
+end