From 0a8690993d572a50b95dd4f1c1903ed00ddb9c2b Mon Sep 17 00:00:00 2001
From: Charlie Stanton <charlie@shtanton.xyz>
Date: Wed, 21 Sep 2022 21:05:34 +0100
Subject: Initial commit

Parses and executes substitute expressions (subexes)

So far subex has the following operations:
- Concatenation of a and b with ab
- Or with |
- Repeat maximally with *
- Repeat minimally with -
- Copy a specific character 'a'
- Copy any character '.'
- Store text matching a regex into slot 's': `$s(regex)`
- Output text in "" including loading from slots with '$'

Regexes support all the same operations as subexes minus storing and outputting

This first implementation gives very little thought to efficiency

Example:

./main 'according to all known laws of aviation' '$1(.-)$m(( .* )| ).*"$m$1"'

This swaps the first and last words of the input string
---
 main/subexast.go | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 main/subexast.go

(limited to 'main/subexast.go')

diff --git a/main/subexast.go b/main/subexast.go
new file mode 100644
index 0000000..7e2f33c
--- /dev/null
+++ b/main/subexast.go
@@ -0,0 +1,117 @@
+package main
+
+import (
+	"fmt"
+)
+
+type SubexAST interface {
+	compileWith(next SubexState) SubexState
+}
+
+type SubexASTConcat struct {
+	first, second SubexAST
+}
+func (ast SubexASTConcat) compileWith(next SubexState) SubexState {
+	return ast.first.compileWith(ast.second.compileWith(next))
+}
+func (ast SubexASTConcat) String() string {
+	return fmt.Sprintf("(%v)(%v)", ast.first, ast.second)
+}
+
+type SubexASTStore struct {
+	match RegexAST
+	slot rune
+}
+func (ast SubexASTStore) compileWith(next SubexState) SubexState {
+	return SubexStoreState {
+		match: ast.match.compileWith(RegexNoneState{}),
+		slot: ast.slot,
+		next: next,
+	}
+}
+func (ast SubexASTStore) String() string {
+	return fmt.Sprintf("$%c(%v)", ast.slot, ast.match)
+}
+
+type SubexASTOr struct {
+	first, second SubexAST
+}
+func (ast SubexASTOr) compileWith(next SubexState) SubexState {
+	return SubexGroupState {
+		ast.first.compileWith(next),
+		ast.second.compileWith(next),
+	}
+}
+
+type SubexASTMaximise struct {
+	content SubexAST
+}
+func (ast SubexASTMaximise) compileWith(next SubexState) SubexState {
+	state := &SubexGroupState {
+		nil,
+		next,
+	}
+	state.first = ast.content.compileWith(state)
+	return state
+}
+func (ast SubexASTMaximise) String() string {
+	return fmt.Sprintf("(%v)*", ast.content)
+}
+
+type SubexASTMinimise struct {
+	content SubexAST
+}
+func (ast SubexASTMinimise) compileWith(next SubexState) SubexState {
+	state := &SubexGroupState {
+		next,
+		nil,
+	}
+	state.second = ast.content.compileWith(state)
+	return state
+}
+func (ast SubexASTMinimise) String() string {
+	return fmt.Sprintf("(%v)-", ast.content)
+}
+
+type SubexASTRepeat struct {
+	content SubexAST
+	min, max int
+}
+func (ast SubexASTRepeat) compileWith(next SubexState) SubexState {
+	for i := ast.min; i < ast.max; i += 1 {
+		next = SubexGroupState {
+			ast.content.compileWith(next),
+			next,
+		}
+	}
+	for i := 0; i < ast.min; i += 1 {
+		next = ast.content.compileWith(next)
+	}
+	return next
+}
+
+type SubexASTCopyRune rune
+func (ast SubexASTCopyRune) compileWith(next SubexState) SubexState {
+	return SubexCopyRuneState{
+		rune: rune(ast),
+		next: next,
+	}
+}
+
+type SubexASTCopyAny struct {}
+func (ast SubexASTCopyAny) compileWith(next SubexState) SubexState {
+	return SubexCopyAnyState{next}
+}
+func (ast SubexASTCopyAny) String() string {
+	return "."
+}
+
+type SubexASTOutput struct {
+	replacement []TransducerOutput
+}
+func (ast SubexASTOutput) compileWith(next SubexState) SubexState {
+	return SubexOutputState{
+		content: ast.replacement,
+		next: next,
+	}
+}
-- 
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