Arithmetic evaluation: Difference between revisions

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@@ Line 327: / Line 327: @@
 =={{header|D}}==
+{{incorrect}}
-{{needs-review}}
- module test;
- import std.stdio;
- int calculate(string expr)
- {
-   string take(int count)
-   {
-     auto res = expr[0 .. count];
-     expr = expr[count .. $];
-     return res;
-   }
-   string peek(int count)
-   {
-     if (expr.length < count) count = expr.length;
-     return expr [0 .. count];
-   }
-   int delegate(int level) descent;
-   // grab the next number from the input expression
-   int getNumber()
-   {
-     int res;
-     // if our "number" is a parantheses-wrapped expression, evaluate it
-     if (peek(1) == "(") { take(1); return descent(0); }
-     while (expr.length)
-     {
-       auto next = peek(1)[0];
-       // if the next character is a digit ...
-       if (next >= '0' && next <= '9')
-       {
-         res = res * 10 + (next-'0');
-         take(1);
-       } else return res;
-     }
-     return res;
-   }
-   // descent evaluates a level-l expression (1: multiplication and division, 0: also addition and subtraction)
-   descent = (int l) {
-     auto num = getNumber; // get the first number of our expression
-     while (expr.length)
-     {
-       auto op = take(1)[0];
-       if (op == ')') return num; // expression end
-       if (op == '*') num *= getNumber;
-       if (op == '/') num /= getNumber;
-       if (l == 1) return num;
-       if (op == '+') num += descent(1);
-       if (op == '-') num -= descent(1);
-     }
-     return num;
-   };
-   return descent(0);
- }
- void main()
- {
-   writefln(calculate("(3+50)*7-9"), ", ", (3+50)*7-9);
- }
-{{works with|DMD|2.007}}
-I'm a D newbie, hope this D code reveals some D unique features.
 <pre>module eval;
 import std.stdio;
@@ Line 398: / Line 336: @@
 // simple stack template
 void push(U)(inout U[] stk, U top) {
-	stk = stk ~ top ;
+  stk = stk ~ top ;
 }
 U pop(U)(inout U[] stk, bool peektop = false) {
-	U top ;
+  U top ;
-	if (stk.length > 0) {
+  if (stk.length > 0) {
-		top = stk[$ - 1] ;
+    top = stk[$ - 1] ;
-		if (!peektop)
+    if (!peektop)
-			stk.length = stk.length - 1 ;
+      stk.length = stk.length - 1 ;
-	} else
+  } else
-		throw new Exception("Invalid Expression") ; // or Empty Stack
+    throw new Exception("Invalid Expression") ; // or Empty Stack
-	return top ;
+  return top ;
 }
 // evalutor function
 T eval(T = long)(string expression) {
-	string[] opr ; // operator stack
+  string[] opr ; // operator stack
-	T[]	num ; // number stack
+  T[] num ; // number stack
-	uint tokensum = 0 ;
+  uint tokensum = 0 ;
-	int[char[]] prece = ["=":0, "(":1, ")":1,"+":2,"-":2,"*":3,"/":3] ;
+  int[char[]] prece = ["=":0, "(":1, ")":1,"+":2,"-":2,"*":3,"/":3] ;
-	void doMath(string op) { // operator executor
+  void doMath(string op) { // operator executor
-		T valR = num.pop() ;
+    T valR = num.pop() ;
-		T valL = num.pop() ;
+    T valL = num.pop() ;
-		switch (op) {
+    switch (op) {
-			case "+": return num.push(valL + valR) ;
+      case "+": return num.push(valL + valR) ;
-			case "-": return num.push(valL - valR) ;
+      case "-": return num.push(valL - valR) ;
-			case "*": return num.push(valL * valR) ;
+      case "*": return num.push(valL * valR) ;
-			case "/": return num.push(valL / valR) ;
+      case "/": return num.push(valL / valR) ;
+    }
-		}
-	}
+  }
-	opr.push("=") ;
+  opr.push("=") ;
-	foreach(m ; RegExp(r"[+*-/()]|\d+").search(expression)) {
+  foreach(m ; RegExp(r"[+*-/()]|\d+").search(expression)) {
-		string token = m.match(0) ;
+    string token = m.match(0) ;
-		tokensum += token.length ;
+    tokensum += token.length ;
-		if (token[0] >= '0' && token[0] <= '9')
+    if (token[0] >= '0' && token[0] <= '9')
-			num.push(to!(T)(token)) ;
+      num.push(to!(T)(token)) ;
-		else if (token == "(")
+    else if (token == "(")
-			opr.push(token) ;
+      opr.push(token) ;
-		else if (token == ")") {
+    else if (token == ")") {
-			while(opr.pop(true) != "(")
+      while(opr.pop(true) != "(")
-				doMath(opr.pop()) ;
+        doMath(opr.pop()) ;
-			opr.pop() ;
+      opr.pop() ;
-		} else {
+    } else {
-			while (prece[opr.pop(true)] >= prece[token])
+      while (prece[opr.pop(true)] >= prece[token])
-				doMath(opr.pop()) ;
+        doMath(opr.pop()) ;
-			opr.push(token) ;
+      opr.push(token) ;
+    }
-		}
-	}
+  }
-	if (tokensum + count(expression, " ") != expression.length)
+  if (tokensum + count(expression, " ") != expression.length)
-		throw new Exception("Invalid Tokens") ;
+    throw new Exception("Invalid Tokens") ;
-	while (opr.length > 1)
+  while (opr.length > 1)
-		doMath(opr.pop()) ;
+    doMath(opr.pop()) ;
-	if (num.length != 1)
+  if (num.length != 1)
-		throw new Exception("Invalid Expression") ;
+    throw new Exception("Invalid Expression") ;
-	return num.pop() ;
+  return num.pop() ;
 }
 void main(string[] args) {
-	foreach(xpr ; std.string.split(join(args[1..$], " "),",")) {
+  foreach(xpr ; std.string.split(join(args[1..$], " "),",")) {
-		try{
+    try{
-			writefln("long: %s = %d", xpr, eval(xpr)) ;
+      writefln("long: %s = %d", xpr, eval(xpr)) ;
-			writefln("int : %s = %d", xpr, eval!(int)(xpr)) ;
+      writefln("int : %s = %d", xpr, eval!(int)(xpr)) ;
+    }
-		}
-		catch (Exception e) {
+    catch (Exception e) {
-			writefln("%s : %s", e.msg, xpr) ;
+      writefln("%s : %s", e.msg, xpr) ;
+    }
-		}
-	}
+  }
+}</pre>
-}
-/*** sample output
-D:\00MY\dmd>dmd eval
-h:\dmd\bin\..\..\dm\bin\link.exe eval,,,user32+kernel32/noi;
-D:\00MY\dmd>eval 1 + * 2, 4*5-3*2, a1 + b,4*(5-3)*2, 128*256*256*256+1
-Invalid Expression : 1 + * 2
-long:  4*5-3*2 = 14
-int :  4*5-3*2 = 14
-Invalid Tokens :  a1 + b
-long: 4*(5-3)*2 = 16
-int : 4*(5-3)*2 = 16
-long:  128*256*256*256+1 = 2147483649
-int :  128*256*256*256+1 = -2147483647
-***/</pre>
 =={{header|Haskell}}==