Data commit

Task/Parsing-RPN-to-infix-conversion/Perl/parsing-rpn-to-infix-conversion.pl

@@ -0,0 +1,30 @@
+use strict;
+use warnings;
+use feature 'say';
+
+my $number   = '[+-/$]?(?:\.\d+|\d+(?:\.\d*)?)';
+my $operator = '[-+*/^]';
+
+my @tests = ('1 2 + 3 4 + ^ 5 6 + ^', '3 4 2 * 1 5 - 2 3 ^ ^ / +');
+
+for (@tests) {
+    my(@elems,$n);
+    $n = -1;
+    while (
+        s/
+            \s* (?<left>$number)   # 1st operand (will be 'left'  in infix)
+            \s+ (?<right>$number)  # 2nd operand (will be 'right' in infix)
+            \s+ (?<op>$operator)   # operator
+            (?:\s+|$)              # more to parse, or done?
+         /
+            ' '.('$'.++$n).' '     # placeholders
+         /ex) {
+            $elems[$n] = "($+{left}$+{op}$+{right})"  # infix expression
+         }
+    while (
+        s/ (\$)(\d+)    # for each placeholder
+         / $elems[$2]   # evaluate expression, substitute numeric value
+         /ex
+        ) { say }       # track progress
+    say '=>' . substr($_,2,-2)."\n";
+}