From 28748660b3723bb10087df65980ca7adfa44f70e Mon Sep 17 00:00:00 2001
From: depsterr <depsterr@protonmail.com>
Date: Thu, 15 Apr 2021 15:49:14 +0200
Subject: [PATCH] implemented if ... then (no else, yet!)

---
 f.sh   | 118 -----------------------------
 for.sh | 232 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 t.sh   |   8 ++
 3 files changed, 240 insertions(+), 118 deletions(-)
 delete mode 100644 f.sh
 create mode 100755 for.sh
 create mode 100755 t.sh

diff --git a/f.sh b/f.sh
deleted file mode 100644
index 6986105..0000000
--- a/f.sh
+++ /dev/null
@@ -1,118 +0,0 @@
-#!/bin/sh
-
-alias :=_newword
-alias ']=_execbody'
-alias xshift='shift 2>/dev/null || printf "Stack underflow\n"'
-
-_stack="" # top is 
-_builtin_dictionary="swap dup rot over drop add sub div mod mul put" # + - / * .
-
-_newword() {
-	name="$1"
-	shift
-	eval "${name}_definition=\"$*\""
-}
-
-_execword() {
-	eval "def=\"\$$1_definition\""
-	eval "def=\"\$$1_definition\""
-	[ "$def" ] || {
-		printf '%s\n' "Error: no word $1"
-		return
-	}
-	_execbody $def
-}
-
-_execbody() {
-	for word in "$@"; do
-		[ "$_debug" ] && {
-			printf 'word %s\nstack %s\n' "$word" "$_stack"
-			read
-		}
-		case "$_builtin_dictionary" in
-			*"$word"*) "_$word" $_stack ;;
-			*) case "$word" in
-				*[0-9]*)   _stack="$word $_stack" ;;
-				*)         _execword "$word" ;;
-			esac
-			;;
-		esac
-	done
-}
-
-_swap() {
-	one="$1"
-	two="$2"
-	xshift
-	_stack="$2 $1 $*"
-}
-
-_dup() {
-	_stack="$1 $*"
-}
-
-_rot() {
-	one="$1"
-	two="$2"
-	thr="$3"
-	xshift
-	xshift
-	xshift
-	_stack="$3 $1 $2 $*"
-}
-
-_over() {
-	_stack="$2 $*"
-}
-
-_drop() {
-	xshift
-	_stack="$*"
-}
-
-_add() {
-	one="$1"
-	two="$2"
-	xshift
-	xshift
-	_stack="$(( one + two )) $*"
-}
-
-_sub() {
-	one="$1"
-	two="$2"
-	xshift
-	xshift
-	_stack="$(( two - one )) $*"
-}
-
-_div() {
-	one="$1"
-	two="$2"
-	xshift
-	xshift
-	_stack="$(( two / one )) $*"
-}
-
-_mod() {
-	one="$1"
-	two="$2"
-	xshift
-	xshift
-	_stack="$(( two % one )) $*"
-}
-
-_mul() {
-	one="$1"
-	two="$2"
-	xshift
-	xshift
-	_stack="$(( one * two )) $*"
-}
-
-_put() {
-	one="$1"
-	xshift
-	printf '%s \n' "$one"
-	_stack="$*"
-}
diff --git a/for.sh b/for.sh
new file mode 100755
index 0000000..a678edd
--- /dev/null
+++ b/for.sh
@@ -0,0 +1,232 @@
+#!/bin/sh
+
+# Weird shell stack based forth "lookalike"
+# recursion can be done by repeating the
+# word. Words cannot have multiple defs
+# in a dictionary.
+# todo:
+#   implement conditionals in _execword :^)
+
+ignore() :
+alias :=_newword
+alias ']=_execbody'
+
+_stack="" # top is 
+_builtin_dictionary="swap dup rot over drop add sub div mod mul put not or and xor eq lt gt ne" # + - / * .
+
+_newword() {
+	name="$1"
+	shift
+	[ "$_debug" ] && {
+		printf '_newword %s: %s\n' "$name" "$*"
+		read
+	}
+	eval "${name}_definition=\"$*\""
+}
+
+_execword() {
+	[ "$_debug" ] && {
+		printf '_execword %s\n' "$1"
+		read
+	}
+	eval "def=\"\$$1_definition\""
+	[ "$def" ] || {
+		printf '%s\n' "Error: no word $1"
+		return
+	}
+	_execbody $def
+}
+
+_execbody() {
+	while [ "$1" ]; do
+		word="$1"
+
+		[ "$_debug" ] && {
+			printf 'word %s\nstack %s\n' "$word" "$_stack"
+			read
+		}
+		case "$_builtin_dictionary" in
+			*"$word"*) "_$word" $_stack ;;
+			*) case "$word" in
+				then) ignore ;;
+				if)
+					[ "${_stack%% *}" = 0 ] && {
+						[ "$_debug" ] && {
+							printf 'failed if, jumping ahead\n'
+							read
+						}
+						_ifcnt=1
+						_thencnt=0
+						while [ "$_ifcnt" != "$_thencnt" ]; do
+							[ "$_debug" ] && { 
+								printf '$1 %s\n' "$1"
+								printf '$* %s\n' "$*"
+								printf 'ifcnt: %s thencnt: %s\n' "$_ifcnt" "$_thencnt"
+								read
+							}
+							shift
+							case "$1" in
+								if)   ignore $(( _ifcnt   += 1 )) ;;
+								then) ignore $(( _thencnt += 1 )) ;;
+								"")   printf 'Unmatched if\n'; return ;;
+							esac
+						done
+					}
+					_drop $_stack
+					shift
+					continue
+					;;
+				*[0-9]*)   _stack="$word $_stack" ;;
+				*)         _execword "$word" ;;
+			esac
+			;;
+		esac
+
+		shift
+	done
+}
+
+_swap() {
+	one="$1"
+	two="$2"
+	shift 2
+	_stack="$two $one $*"
+}
+
+_dup() {
+	_stack="$1 $*"
+}
+
+_rot() {
+	one="$1"
+	two="$2"
+	thr="$3"
+	shift 3
+	_stack="$thr $one $two $*"
+}
+
+_over() {
+	_stack="$2 $*"
+}
+
+_drop() {
+	shift
+	_stack="$*"
+}
+
+_add() {
+	one="$1"
+	two="$2"
+	shift 2
+	_stack="$(( one + two )) $*"
+}
+
+_sub() {
+	one="$1"
+	two="$2"
+	shift 2
+	_stack="$(( two - one )) $*"
+}
+
+_div() {
+	one="$1"
+	two="$2"
+	shift 2
+	_stack="$(( two / one )) $*"
+}
+
+_mod() {
+	one="$1"
+	two="$2"
+	shift 2
+	_stack="$(( two % one )) $*"
+}
+
+_mul() {
+	one="$1"
+	two="$2"
+	shift 2
+	_stack="$(( one * two )) $*"
+}
+
+_put() {
+	one="$1"
+	shift
+	printf '%s \n' "$one"
+	_stack="$*"
+}
+
+_not() {
+	one="$1"
+	shift
+	_stack="$(( ~ one )) $*"
+}
+
+_or() {
+	one="$1"
+	two="$2"
+	shift 2
+	_stack="$(( one | two )) $*"
+}
+
+_and() {
+	one="$1"
+	two="$2"
+	shift 2
+	_stack="$(( one & two )) $*"
+}
+
+_xor() {
+	one="$1"
+	two="$2"
+	shift 2
+	_stack="$(( one ^ two )) $*"
+}
+
+_eq() {
+	one="$1"
+	two="$2"
+	shift 2
+	if [ "$one" -eq "$two" ]; then
+		_stack="$(( ~ 0 )) $*"
+	else
+		_stack="$(( 0 )) $*"
+	fi
+}
+
+_lt() {
+	one="$1"
+	two="$2"
+	shift 2
+	if [ "$two" -lt "$one" ]; then
+		_stack="$(( ~ 0 )) $*"
+	else
+		_stack="$(( 0 )) $*"
+	fi
+}
+
+_gt() {
+	one="$1"
+	two="$2"
+	shift 2
+	if [ "$two" -gt "$one" ]; then
+		_stack="$(( ~ 0 )) $*"
+	else
+		_stack="$(( 0 )) $*"
+	fi
+}
+
+_ne() {
+	one="$1"
+	two="$2"
+	shift 2
+	if [ "$two" -ne "$one" ]; then
+		_stack="$(( ~ 0 )) $*"
+	else
+		_stack="$(( 0 )) $*"
+	fi
+}
+
+# definitions in forsh
+: true  not false ;
+: false 0 ;
diff --git a/t.sh b/t.sh
new file mode 100755
index 0000000..070bd7d
--- /dev/null
+++ b/t.sh
@@ -0,0 +1,8 @@
+#!/bin/sh
+. ./for.sh
+
+# _debug=y
+
+: pow dup 1 gt if 1 sub over swap pow mul then dup 1 gt not if drop then ; # b e -- x
+
+] 2 8 pow put