Arithmetic evaluation: Difference between revisions

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 This example was made rather more complex by the requirement of generating an AST tree. With a Scala distribution there are many examples of arithmetic parsers, as small as half a dozen lines.
+=={{header|Sidef}}==
+Translation of [[JavaScript]].
+<lang ruby>func evalArithmeticExp(s) {
+    func evalExp(s) {
+        func operate(s, op) {
+           s.split(op).map{|c|c.toNum}.reduce(op);
+        }
+        func add(s) {
+            operate(s.replace(/^\+/,'').replace(/\++/,'+'), '+');
+        }
+        func subtract(s) {
+            s.gReplace!(/(\+-|-\+)/,'-');
+            if (s.match(/--/)) {
+                return(add(s.replace(/--/,'+')));
+            }
+            b = (s.split('-')).len == 3
+                ? (-1 * b[1].toNum - b[2].toNum)
+                : (operate(s, '-'))
+        }
+        s.gReplace!(/[()]/,'').gReplace!(/-\+/, '-');
+        var reM  = /\*/;
+        var reMD = qr"(\d+\.?\d*\s*[*/]\s*[+-]?\d+\.?\d*)";
+        var reA  = /\d\+/;
+        var reAS = /(-?\d+\.?\d*\s*[+-]\s*[+-]?\d+\.?\d*)/;
+        var match;
+        while (match = s.match(reMD)) {
+            cap = (match.captures.first) =~ reM ??
+                ? (s.replace!(reMD, operate(cap, '*').to_s))
+                : (s.replace!(reMD, operate(cap, '/').to_s))
+        }
+        while (match = s.match(reAS)) {
+            cap = (match.captures.first) =~ reA ??
+                ? (s.replace!(reAS,      add(cap).to_s))
+                : (s.replace!(reAS, subtract(cap).to_s));
+        }
+        return(s);
+    }
+    var rePara = /(\([^\(\)]*\))/;
+    s = (s.split.join('').replace(/^\+/,''));
+    while (var match = s.match(rePara)) {
+        s.replace!(rePara, evalExp(match.captures.first));
+    }
+    return(evalExp(s).toNum);
+}</lang>
+Testing the function:
+<lang ruby>for [
+     ['2+3'                                      =>        5],
+     ['-4-3'                                     =>       -7],
+     ['-+2+3/4'                                  =>    -1.25],
+     ['2*3-4'                                    =>        2],
+     ['2*(3+4)+2/4'                              => 2/4 + 14],
+     ['2*-3--4+-0.25'                            =>    -2.25],
+     ['2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10' =>     7000],
+    ] { |expr, res|
+    var num = (evalArithmeticExp(expr)) == res || (
+            "Error occurred on expression '#{expr}': got '#{num}' instead of '#{res}'\n".die;
+    );
+    "%-45s == %10g\n".printf(expr, num);
+}</lang>
 =={{header|Tcl}}==