tasks a-s

Task/Parsing-RPN-to-infix-conversion/Tcl/parsing-rpn-to-infix-conversion.tcl

@@ -0,0 +1,39 @@
+package require Tcl 8.5
+
+# Helpers
+proc precassoc op {
+    dict get {^ {4 right} * {3 left} / {3 left} + {2 left} - {2 left}} $op
+}
+proc pop stk {
+    upvar 1 $stk s
+    set val [lindex $s end]
+    set s [lreplace $s end end]
+    return $val
+}
+
+proc rpn2infix rpn {
+    foreach token $rpn {
+	switch $token {
+	    "^" - "/" - "*" - "+" - "-" {
+		lassign [pop stack] bprec b
+		lassign [pop stack] aprec a
+		lassign [precassoc $token] p assoc
+		if {$aprec < $p || ($aprec == $p && $assoc eq "right")} {
+		    set a "($a)"
+		}
+		if {$bprec < $p || ($bprec == $p && $assoc eq "left")} {
+		    set b "($b)"
+		}
+		lappend stack [list $p "$a $token $b"]
+	    }
+	    default {
+		lappend stack [list 9 $token]
+	    }
+	}
+	puts "$token -> $stack"
+    }
+    return [lindex $stack end 1]
+}
+
+puts [rpn2infix {3 4 2 * 1 5 - 2 3 ^ ^ / +}]
+puts [rpn2infix {1 2 + 3 4 + ^ 5 6 + ^}]