package main import "slices" type NodeType int // This is a list of the possible node types const ( CHARACTER NodeType = iota PIPE CONCATENATE KLEENE QUESTION PLUS ASSERTION ) var INFINITE_REPS int = -1 // Represents infinite reps eg. the end range in {5,} // This represents a node in the postfix representation of the expression type postfixNode struct { nodetype NodeType contents []rune // Contents of the node - the length of this would only be >1 if the node represents a character class startReps int // How many times the node should be repeated - used with numeric specifiers endReps int } // Creates a new escaped node - the given character is assumed to have been preceded by a backslash func newEscapedNode(c rune) postfixNode { toReturn := postfixNode{} toReturn.startReps = 1 toReturn.endReps = 1 switch c { case 's': // Whitespace toReturn.nodetype = CHARACTER toReturn.contents = append(toReturn.contents, whitespaceChars...) case 'S': // Non-whitespace - I am doing this in a fancy way, generating all dot characters, then removing whitespace characters from it toReturn.nodetype = CHARACTER toReturn.contents = append(toReturn.contents, slices.DeleteFunc(dotChars(), func(r rune) bool { return slices.Contains(whitespaceChars, r) })...) case 'd': // Digits toReturn.nodetype = CHARACTER toReturn.contents = append(toReturn.contents, digitChars...) case 'D': // Non-digits - same fancy way as 'S' toReturn.nodetype = CHARACTER toReturn.contents = append(toReturn.contents, slices.DeleteFunc(dotChars(), func(r rune) bool { return slices.Contains(digitChars, r) })...) case 'w': // word character toReturn.nodetype = CHARACTER toReturn.contents = append(toReturn.contents, wordChars...) case 'W': // Non-word character - same fancy way as 'S' and 'D' toReturn.nodetype = CHARACTER toReturn.contents = append(toReturn.contents, slices.DeleteFunc(dotChars(), func(r rune) bool { return slices.Contains(wordChars, r) })...) case 'b', 'B': toReturn.nodetype = ASSERTION toReturn.contents = append(toReturn.contents, c) default: // None of the above - append it as a regular character toReturn.nodetype = CHARACTER toReturn.contents = append(toReturn.contents, c) } return toReturn } // Creates and returns a postfixNode based on the given contents func newPostfixNode(contents ...rune) postfixNode { if len(contents) < 1 { panic("Empty node.") } to_return := postfixNode{} to_return.startReps = 1 to_return.endReps = 1 if len(contents) > 1 { // If the node has more than element, it must be a character class - the type must be CHARACTER to_return.nodetype = CHARACTER to_return.contents = contents } else { // Node has one element, could be anything switch contents[0] { case '+': to_return.nodetype = PLUS case '?': to_return.nodetype = QUESTION case '*': to_return.nodetype = KLEENE case '|': to_return.nodetype = PIPE case CONCAT: to_return.nodetype = CONCATENATE case '^', '$': to_return.nodetype = ASSERTION default: to_return.nodetype = CHARACTER } to_return.contents = append(to_return.contents, contents...) } return to_return } // Creates a character node, regardless of the contents func newPostfixCharNode(contents ...rune) postfixNode { toReturn := postfixNode{} toReturn.nodetype = CHARACTER toReturn.contents = append(toReturn.contents, contents...) return toReturn }