From ed7f050a0f6d008b327098ad930c4873d3b3e461 Mon Sep 17 00:00:00 2001
From: Alexander Sulfrian <alexander@sulfrian.net>
Date: Wed, 13 Oct 2010 11:52:54 +0200
Subject: changed repository layout

---
 calc/calc.erl | 164 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 164 insertions(+)
 create mode 100644 calc/calc.erl

(limited to 'calc/calc.erl')

diff --git a/calc/calc.erl b/calc/calc.erl
new file mode 100644
index 0000000..4869104
--- /dev/null
+++ b/calc/calc.erl
@@ -0,0 +1,164 @@
+-module(calc).
+-export([eval/1]).
+
+%% num := [-] 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
+num(Input) ->
+    num(Input, []).
+
+num([Current|Input], Num) when ($0 =< Current) and ($9 >= Current) ->
+    num(Input, Num ++ [Current]);
+num([Head|_], "-") ->
+    {error, {unexpected, list_to_atom([Head])}};
+num(Input, []) ->
+    {ok, {Input, []}};
+num(Input, Num) ->
+    {ok, {Input, list_to_integer(Num)}}.
+
+%% bracket := [-] ( '(' sum '}' | num )
+bracket([$-|Input]) ->
+    case bracket(Input) of
+	{ok, {Tail, []}} ->
+	    {error, {expected_number, {before, Tail}}};
+	{ok, {Tail, Result}} ->
+	    {ok, {Tail, -1 * Result}};
+	{error, Why} ->
+	    {error, Why}
+    end;
+bracket([$(|Input]) ->
+    case sum(Input) of
+	{ok, {Tail, Result}} ->
+	    bracketCheck(Tail, Result);
+	{error, Why} ->
+	    {error, Why}
+    end;
+bracket(Input) ->
+    num(Input).
+
+bracketCheck([$)|Tail], Result) ->
+    {ok, {Tail, Result}};
+bracketCheck(_, _) ->
+    {error, missing_bracket}.
+
+%% factor := num [ ^ factor ]
+factor(Input) ->
+    case bracket(Input) of
+	{ok, {Tail, Number2}} ->
+	    factorExtended(Tail, Number2);
+	{error, Why} ->
+	    {error, Why}
+    end.
+
+factor([Head|Input], Number1) ->
+    case bracket([Head|Input]) of
+	{ok, {Tail, Number2}} ->
+	    Result = math:pow(Number1, Number2),
+	    factorExtended(Tail, Result);
+	{error, Why} ->
+	    {error, Why}
+    end;
+factor([], _) ->
+    {error, unexpected_end_of_input}.
+
+factorExtended([$ |Tail], Result) ->
+    factorExtended(Tail, Result);
+factorExtended([$^|Tail], Result) ->
+    factor(Tail, Result);
+factorExtended(Tail, Result) ->
+    {ok, {Tail, Result}}.
+
+%% term := factor [ ( * | / ) term ]
+term(Input) ->
+    case factor(Input) of
+	{ok, {Tail, Result}} ->
+	    termExtended(Tail, Result);
+	{error, Why} ->
+	    {error, Why}
+    end.
+
+term([Head|Input], Number1, Operator) ->
+    case factor([Head|Input]) of
+	{ok, {Tail, Number2}} ->
+	    case calc(Number1, Operator, Number2) of
+		{ok, Result} ->
+		    termExtended(Tail, Result);
+		{error, Why} ->
+		    {error, Why}
+	    end;
+
+	{error, Why} ->
+	    {error, Why}
+    end;
+term([], _, _) ->
+    {error, unexpected_end_of_input}.
+
+termExtended([$ |Tail], Result) ->
+    termExtended(Tail, Result);
+termExtended([$*|Tail], Result) ->
+    term(Tail, Result, $*);
+termExtended([$/|Tail], Result) ->
+    term(Tail, Result, $/);
+termExtended(Tail, Result) ->
+    {ok, {Tail, Result}}.
+
+%% sum := term [ ( + | - ) sum ]
+sum([$+|Input]) ->
+    sum(Input);
+sum(Input) ->
+    case term(Input) of
+	{ok, {Tail, Result}} ->
+	    sumExtended(Tail, Result);
+	{error, Why} ->
+	    {error, Why}
+    end.
+
+sum([Head|Input], Number1, Operator) ->
+    case term([Head|Input]) of
+	{ok, {Tail, Number2}} ->
+	    case calc(Number1, Operator, Number2) of
+		{ok, Result} ->
+		    sumExtended(Tail, Result);
+		{error, Why} ->
+		    {error, Why}
+	    end;
+
+	{error, Why} ->
+	    {error, Why}
+    end;
+sum([], _, _) ->
+    {error, unexpected_end_of_input}.
+
+sumExtended([$ |Tail], Result) ->
+    sumExtended(Tail, Result);
+sumExtended([$+|Tail], Result) ->
+    sum(Tail, Result, $+);
+sumExtended([$-|Tail], Result) ->
+    sum(Tail, Result, $-);
+sumExtended(Tail, Result) ->
+    {ok, {Tail, Result}}.
+
+%% helper function to do the calculations
+calc(Number1, $+, Number2) ->
+    {ok, Number1 + Number2};
+calc(Number1, $-, Number2) ->
+    {ok, Number1 - Number2};
+calc(Number1, $*, Number2) ->
+    {ok, Number1 * Number2};
+calc(Number1, $/, Number2) when (Number2 /= 0) ->
+    {ok, Number1 / Number2};
+calc(_, $/, _) ->
+    {error, division_zero};
+calc(_,_,_) ->
+    {error, invalid_operator}.
+
+eval(Formular) ->
+    case sum([X || X <- Formular, X /= $ ]) of
+	{ok, {Tail, Result}} ->
+	    evalCheck(Tail, Result);
+	{error, Why} ->
+	    {error, Why}
+    end.
+
+evalCheck([], Result) ->
+    {ok, Result};
+evalCheck(Tail, _) ->
+    {error, {unexpected_garbage_at_end_of_input, Tail}}.
-- 
cgit v1.2.3