From 184118c1522ee4e78a0588fcac8eb235f512b599 Mon Sep 17 00:00:00 2001
From: Charlie Stanton <charlie@shtanton.xyz>
Date: Fri, 21 Apr 2023 11:19:18 +0100
Subject: Add :xyz: replacement syntax that removes whatever is before it and
 inserts whatever is inside it

---
 subex/parse.go | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

(limited to 'subex/parse.go')

diff --git a/subex/parse.go b/subex/parse.go
index 52488a7..4e7a3f6 100644
--- a/subex/parse.go
+++ b/subex/parse.go
@@ -166,7 +166,7 @@ func parseReplacement(l RuneReader) (output []OutputContent) {
 		switch r {
 			case eof:
 				panic("Missing closing \"")
-			case '=', '^':
+			case '=', '^', ':':
 				break loop
 			case '$':
 				slot := l.Next()
@@ -281,7 +281,7 @@ func parseSubex(l RuneReader, minPower int) SubexAST {
 		case '[':
 			rangeParts := parseRangeSubex(l)
 			lhs = SubexASTRange {rangeParts}
-		case ')', '|', ';', '{', '+', '-', '*', '/', '!', '$':
+		case ')', '|', ';', '{', '+', '-', '*', '/', '!', '$', ':':
 			l.Rewind()
 			return nil
 		case '=':
@@ -358,9 +358,19 @@ func parseSubex(l RuneReader, minPower int) SubexAST {
 				if slot == eof {
 					panic("Missing slot character")
 				}
-				lhs = SubexASTStore{
-					Match: lhs,
-					Slot: slot,
+				if slot == '_' {
+					lhs = SubexASTDiscard {lhs}
+				} else {
+					lhs = SubexASTStore{
+						Match: lhs,
+						Slot: slot,
+					}
+				}
+			case r == ':' && minPower <= 4:
+				replacement := parseReplacement(l)
+				lhs = SubexASTConcat {
+					SubexASTDiscard {lhs},
+					SubexASTOutput {replacement},
 				}
 			case r == '|' && minPower <= 8:
 				rhs := parseSubex(l, 9)
-- 
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