initial

1 files changed, 78 insertions, 0 deletions

diff --git a/itr.go b/itr.go
new file mode 100644
index 0000000..68616b7
--- /dev/null
+++ b/itr.go
@@ -0,0 +1,78 @@
+package lexpr
+
+import "context"
+
+func infixToRpn(ctx context.Context, tokens <-chan Token) <-chan Token {
+	out := make(chan Token)
+	stack := TokenStack{}
+	go func() {
+		defer func() {
+			if len(stack) > 0 {
+				for {
+					if stack.Head().typ == lp {
+						out <- Token{
+							typ:   tokError,
+							value: "invalid brakets",
+						}
+						break
+					}
+					out <- stack.Pop()
+					if len(stack) == 0 {
+						break
+					}
+				}
+			}
+			close(out)
+		}()
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case tkn, ok := <-tokens:
+				if !ok {
+					return
+				}
+				switch tkn.typ {
+				case number, word, str, tokError:
+					out <- tkn
+				case funct:
+					stack.Push(tkn)
+				case sep:
+					for stack.Head().typ != lp {
+						if len(stack) == 0 {
+							out <- Token{
+								typ:   tokError,
+								value: "no arg separator or opening braket",
+							}
+							return
+						}
+						out <- stack.Pop()
+					}
+				case op:
+					for len(stack) > 0 && (stack.Head().typ != op || (stack.Head().priority >= tkn.priority)) {
+						out <- stack.Pop()
+					}
+					stack.Push(tkn)
+				case lp:
+					stack.Push(tkn)
+				case rp:
+					for stack.Head().typ != lp {
+						if len(stack) == 0 {
+							out <- Token{
+								typ:   tokError,
+								value: "no opening braket",
+							}
+							return
+						}
+						out <- stack.Pop()
+					}
+					stack.Pop()
+					if stack.Head().typ == funct {
+						out <- stack.Pop()
+					}
+				}
+			}
+		}
+	}()
+	return out
+}