Data commit

Task/S-expressions/Wren/s-expressions.wren

@@ -0,0 +1,88 @@
+import "/pattern" for Pattern
+import "/fmt" for Fmt
+
+var INDENT = 2
+
+var parseSExpr = Fn.new { |str|
+    var ipat = " \t\n\f\v\r()\""
+    var p = Pattern.new("""+0/s["+0^""|(|)|"|+1/I]""", Pattern.within, ipat)
+    var t = p.findAll(str).map { |m| m.text }.toList
+    if (t.count == 0) return null
+    var o = false
+    var c = 0
+    for (i in t.count-1..0) {
+        var ti = t[i].trim()
+        var nd = Num.fromString(ti)
+        if (ti == "\"") return null
+        if (ti == "(") {
+            t[i] = "["
+            c = c + 1
+        } else if (ti == ")") {
+            t[i] = "]"
+            c = c - 1
+        } else if (nd) {
+            var ni = Num.fromString(ti)
+            t[i] = ni ? ni.toString : nd.toString
+        } else if (ti.startsWith("\"")) { // escape embedded double quotes
+            var temp = ti[1...-1]
+            t[i] = "\"" + temp.replace("\"", "\\\"") + "\""
+        }
+        if (i > 0 && t[i] != "]" && t[i - 1].trim() != "(") t.insert(i, ", ")
+        if (c == 0) {
+            if (!o) o = true else return null
+        }
+    }
+    return (c != 0) ? null : t
+}
+
+var toSExpr = Fn.new { |tokens|
+    for (i in 0...tokens.count) {
+        if (tokens[i] == "[") {
+            tokens[i] = "("
+        } else if (tokens[i] == "]") {
+            tokens[i] = ")"
+        } else if (tokens[i] == ", ") {
+            tokens[i] = " "
+        } else if (tokens[i].startsWith("\"")) { // unescape embedded quotes
+            var temp = tokens[i][1...-1]
+            tokens[i] = "\"" + temp.replace("\\\"", "\"") + "\""
+        }
+    }
+    return tokens.join()
+}
+
+var prettyPrint = Fn.new { |tokens|
+    var level = 0
+    for (t in tokens) {
+        var n
+        if (t == ", " || t == " ") {
+            continue
+        } else if (t == "[" || t == "(") {
+            n = level * INDENT + 1
+            level = level + 1
+        } else if (t == "]" || t == ")") {
+            level = level - 1
+            n = level * INDENT + 1
+        } else {
+            n = level * INDENT + t.count
+        }
+        Fmt.print("$*s", n, t)
+    }
+}
+
+var str = """((data "quoted data" 123 4.5)""" + "\n" +
+          """ (data (!@# (4.5) "(more" "data)")))"""
+var tokens = parseSExpr.call(str)
+if (!tokens) {
+    System.print("Invalid s-expr!")
+} else {
+    System.print("Native data structure:")
+    System.print(tokens.join())
+    System.print("\nNative data structure (pretty print):")
+    prettyPrint.call(tokens)
+
+    System.print("\nRecovered S-Expression:")
+    System.print(toSExpr.call(tokens))
+    System.print("\nRecovered S-Expression (pretty print):")
+    prettyPrint.call(tokens)
+}