=== modified file 'common.zsh'
--- common.zsh	2017-12-12 22:50:13 +0000
+++ common.zsh	2017-12-12 17:03:06 +0000
@@ -8,10 +8,7 @@
 OUT=$3
 FUNCDIR=${0:h:a}/functions
 TARGET=${BASE##*/}.${${${DO:t}%.do}#default.}
-typeset -g value_counter last_var __check_deps__
-value_counter=0
-typeset -ga finish_hooks args
-typeset -gA vars vals
+typeset -ga finish_hooks
 
 # helper that prints out error message and exits
 die() {
@@ -32,106 +29,6 @@
 	done
 }
 
-# Logical variable handling
-ground() {
-	(($# == 1)) || die
-	(($+vals[$vars[$1]]))
-}
-
-getvars() {
-	local -a ground_vars
-	local k v
-	if (($#)); then
-		for k in $@; do
-			ground $k && ground_vars+=( $k )
-		done
-	else
-		for k v in ${(kv)vars}; do
-			(($+vals[$v])) && ground_vars+=( $k )
-		done
-	fi
-	printf 'local %s\n' ${(j: :)ground_vars}
-	for k in $ground_vars; do
-		printf '%s=$vals[$vars[%s]]\n' $k $k
-	done
-}
-
-setvar() {
-	(($# == 2)) || die
-	if ground $1; then
-		[[ $vals[$vars[$1]] == $2 ]] \
-			|| die "$0: Could not unify $1 (value ${(qqq)vals[$vars[$1]]}) with ${(qqq)2}"
-	else
-		vals[$vars[$1]]=$2
-	fi
-}
-
-defvar() {
-	# set variable only if unbound
-	if ! ground $1; then
-		setvar $1 $2
-	fi
-}
-
-fresh() {
-	(($# < 2)) || die
-	value_counter=$[value_counter + 1]
-	last_var=${1:-_$value_counter}
-	(($+vars[$last_var])) && die "$0: Variable already defined: $1"
-	vars[$last_var]=$value_counter
-}
-
-unify_replace() {
-	# replace internal representation of var $1 with $2, effectively unifying them
-	local k v
-	for k v in ${(kv)vars}; do
-		[[ $v == $1 ]] && vars[$k]=$2
-	done
-}
-
-unify() {
-	(($# == 2)) || die
-	if ground $1; then
-		if ground $2; then
-			[[ $vals[$vars[$1]] == $vals[$vars[$2]] ]] \
-				|| die "$0: Could not unify $1 (value ${(qqq)vals[$vars[$1]]}) with $2 (value ${(qqq)vals[$vars[$2]]})"
-			# deduplicate value
-			unify_replace $vars[$1] $vars[$2]
-			unset "vals[$vars[$1]]"
-		else
-			unify_replace $vars[$2] $vars[$1]
-		fi
-	else
-		unify_replace $vars[$1] $vars[$2]
-	fi
-}
-
-args() {
-	(($#args)) && die "$0: args already defined"
-	local arg
-	local -A unseen
-	unseen=( "${(kv@}vars}" )
-	for arg in "$@"; do
-		case $arg in
-			(*=*)
-				args+=( ${arg%%=*} )
-				defvar ${arg%%=*} ${arg#*=}
-				;;
-			(*!)
-				args+=( ${arg%!} )
-				ground ${arg%!} \
-					|| die "$0: Required argument ${(qqq)${arg%!}} not defined"
-				;;
-			(*) args+=( $arg );;
-		esac
-	done
-	for arg in $args; do
-		unset "unseen[$arg]"
-	done
-	(($#unseen)) && die "$0: Undefined arguments passed: ${(k)unseen}"
-}
-
-# argument formatting
 decode_argstr() {
 	local base
 	base=${BASE##*/}
@@ -141,8 +38,8 @@
 	done
 	tr <<<$base _- /+ | base64 -d
 }
-
 decode_args() {
+	typeset -gA vars
 	local arg decoded
 	decoded=$(decode_argstr) \
 		|| die "Unable to decode: ${(qqq)${BASE##*/}}"
@@ -152,36 +49,27 @@
 			echo >&2 "Malformed argument: ${(qqq)arg}"
 			exit 1
 		fi
-		fresh ${arg%%=*}
-		setvar ${arg%%=*} ${arg#*=}
+		if (( $+vars[${arg%%=*}] )); then
+			echo >&2 "Duplicate argument: ${arg%%=*}"
+			exit 1
+		fi
+		vars[${arg%%=*}]=${arg#*=}
 	done
 }
 
-print_meta() {
-	local -a arglist unifications
-	local -A names
-	local k v
-
-	for k in ${(o)args}; do
-		if (($+names[$vars[$k]])); then
-			names[$vars[$k]]+=" $k"
-		else
-			names[$vars[$k]]=$k
-		fi
-	done
-
-	for k v in ${(kv)names}; do
-		[[ $v == *' '* ]] && unifications+=( $v )
-		(( $+vals[$k] )) && arglist+=( ${v%% *}=$vals[$k]
-	done
-
-	arglist=( ${(o)arglist} __check_deps__=$__check_deps__ )
-	(( $#unifications )) && arglist=( __unified__=${(vF)} $arglist )
+print-meta() {
+	local -a arglist
+	local k
+	for k in ${(ko)vars}; do
+		arglist+=( "$k=$vars[$k]" )
+	done
 	printf "%s" "${(j::)arglist}"
 }
 
-start_info(){
-	info "called: ${(qqq)$(decode_argstr)}"
+start-info(){
+	local name
+	name=${${${DO:t}%.do}#default.}
+	info "entering: $name $(decode_argstr)"
 }
 
 add_finish_hook() {
@@ -195,23 +83,51 @@
 	done
 }
 
+finish-info(){
+	local name
+	name=${${${DO:t}%.do}#default.}
+	info "finished: $name $(decode_argstr)"
+	(($+vars[sha256sum])) && info "$name produced: $vars[sha256sum]"
+	(($+vars[build_dir])) && info "$name build in: $vars[build_dir]"
+	(($+vars[filename])) && info "$name filename: $vars[filename]"
+}
+
 finish() {
 	run_finish_hooks
-	print_meta >$OUT
+	finish-info
+	print-meta >$OUT
 	exit 0
 }
 
-# dependency tracking
+# set $vars parameter if it's empty (ie. set default value)
+defvar() {
+	if ! (($+vars[$1])); then
+		vars[$1]=$2
+	fi
+}
+
+# check if variables are nonempty
+checkvars() {
+	local var
+	local -a empty
+	for var in "$@"; do
+		if ! (($+vars[$var])); then
+			empty+=( $var )
+		fi
+	done
+	(( $#empty )) && die "required parameters are empty: ${(@q)empty}"
+}
+
 dep_add_file() {
 	local out
 	out=$(sha256sum $1) || die
-	__check_deps__+='if { test -e '${(qqq)1}$' }\n'
-	__check_deps__+='if { pipeline -d { printf "%s\n" '${(qqq)out}$' } sha256sum -c }\n'
+	vars[__check_deps__]+='if { test -e '${(qqq)1}$' }\n'
+	vars[__check_deps__]+='if { pipeline -d { printf "%s\n" '${(qqq)out}$' } sha256sum -c }\n'
 }
 
 dep_add_missing() {
 	[[ -e $1 ]] || die "$0: ${(qqq)1} exists"
-	__check_deps__+='if -n { test -e '${(qqq)1}$' }\n'
+	vars[__check_deps__]+='if -n { test -e '${(qqq)1}$' }\n'
 }
 
 dep_add_file_or_missing() {
@@ -230,7 +146,7 @@
 	out=$(tar -cvp -C $1 --mtime=1970-01-01 . | sha256sum -)
 	(( ${(j.|.)pipestatus} )) \
 		&& die "$0: Failed to checksum directory: ${(qqq)1}"
-	__check_deps__+='if { pipeline -d { printf "%s\n" '${(qqq)out}'} fdmove 3 1 pipeline -d { tar -cvp --mtime=1970-01-01 -C '${(qqq)1}$' . } sha256sum -c /proc/self/fd/3 }\n'
+	vars[__check_deps__]+='if { pipeline -d { printf "%s\n" '${(qqq)out}'} fdmove 3 1 pipeline -d { tar -cvp --mtime=1970-01-01 -C '${(qqq)1}$' . } sha256sum -c /proc/self/fd/3 }\n'
 }
 
 dep_add_dir_mtimes() {
@@ -239,34 +155,70 @@
 	out=$(tar -cvp -C $1 . | sha256sum -)
 	(( ${(j.|.)pipestatus} )) \
 		&& die "$0: Failed to checksum directory: ${(qqq)1}"
-	__check_deps__+='if { pipeline -d { printf "%s\n" '${(qqq)out}'} fdmove 3 1 pipeline -d { tar -cvp -C '${(qqq)1}$' . } sha256sum -c /proc/self/fd/3 }\n'
+	vars[__check_deps__]+='if { pipeline -d { printf "%s\n" '${(qqq)out}'} fdmove 3 1 pipeline -d { tar -cvp -C '${(qqq)1}$' . } sha256sum -c /proc/self/fd/3 }\n'
 }
 
 ifchange() {
 	local arg
 	redo-ifchange "$@" || die "failed to build one or more dependencies: $*"
 	for arg in "$@"; do
-		__check_deps__+='if { redo-ifchange '${(qqq)arg}$' }\n'
+		vars[__check_deps__]+='if { redo-ifchange '${(qqq)arg}$' }\n'
 		dep_add_file $arg
 	done
 }
 
-exit_unchanged() {
+parse-previous() {
+	typeset -g previous_parsed has_previous
+	typeset -gA previous
+	local arg
+
+	(($previous_parsed)) && return
+
+	if ! [[ -f $FILE ]]; then
+		info "changed: missing $FILE"
+		previous_parsed=1
+		has_previous=0
+		return 1
+	fi
+
+	for arg in "${(s::Q)$(<$FILE)}"; do
+		if [[ "$arg" != *=* ]]; then
+			die "$0: Malformed argument: ${(qqq)arg}"
+		fi
+		if (( $+previous[${arg%%=*}] )); then
+			die "$0: Duplicate argument: ${arg%%=*}"
+		fi
+		previous[${arg%%=*}]=${arg#*=}
+	done
+
+	previous_parsed=1
+	has_previous=1
+}
+
+exit-unchanged() {
 	info "$DO:t unchanged, skipping build"
 	cp $FILE $OUT
 	exit 0
 }
 
 depend() {
-	# usage: depend <name> [<arguments>]
+	# TODO: edit this comment copied over from confz
+	# usage: require <name> [<variables>] [-- <arguments>]
 	# where:
-	#   <name> is a dependency name as defined by dofile `default.<name>.do`
-	#   <arguments> are named arguments to pass to dependency in following forms:
-	#       foo=bar  -- sets argument foo to value "bar"
-	#       foo:     -- unifies argument foo with variable foo in the caller
-	#       foo:bar  -- unifies argument foo with variable bar in the caller
+	#   <name> is a dependency name as defined by function confz_<name>_check
+	#   <variables> are variable assignments in the form of:
+	#       foo=bar  -- sets ${vars[foo]} in calee to value "bar"
+	#       :foo  -- passes ${vars[foo]} from caller to calee
+	#       ?foo=bar -- sets ${vars[foo]} in calee to value of ${vars[bar]}
+	#                   iff it is defined in the caller
+	#       ?foo -- passes ${vars[foo]} from caller to calee iff it is defined
+	#               in the caller
+	#       %foo  -- passes ${vars[foo]} from callee to caller
+	#       %foo=bar  -- passes ${vars[foo]} from callee
+	#                    to variable ${vars[bar]} of caller
+	#   <arguments> are arguments passed to the dependency function
 
-	local name
+	local name outer inner
 	local target
 	local -a new_vars run
 	local -A lift
@@ -277,21 +229,16 @@
 	# parse variable assignments
 	while (( $# )); do
 		case $1 in
-			(*=*)  new_vars+=( ${1%%=*}=${1#*=} );;
-			(*:)
-				if ground ${1%:}; then
-					new_vars+=( ${1%:}=$vals[$vars[${1%:}]] )
-				else
-					lift[${1%:}]=${1%:}
-				fi
-				;;
-			(*:*)
-				if ground ${1#*:}; then
-					new_vars+=( ${1%:*}=$vals[$vars[${1#*:}]] )
-				else
-					lift[${1%:*}]=${1#*:}
-				fi
-				;;
+			(:*)   ((${+vars[${1#:}]})) || \
+				die "variable ${(qqq)1#:} not set, passed as :argument"
+				new_vars+=( ${1#:}="${vars[${1#:}]}" );;
+			(\?*=*) (($+vars[${${1#\?}#*=})) && \
+				new_vars+=( ${${1#\?}%%=*}="$vars[${${1#\?}#*=}" );;
+			(\?*)  ((${+vars[${1#\?}]})) && \
+				new_vars+=( ${1#\?}="${vars[${1#\?}]}" );;
+			(%*=*) lift[${${1#%}%%=*}]=${${1#%}#*=};;
+			(%*)   lift[${1#%}]=${1#%};;
+			(*=*)  new_vars+=( "${1%%=*}"="${1#*=}" );;
 			(--)   shift; break;;
 			(*)    die "$name: unrecognised argument: ${(qqq)1}";;
 		esac
@@ -321,68 +268,24 @@
 			fi
 			lift_vars[${arg%%=*}]=${arg#*=}
 		done
-		if (($+lift_vars[__unified__])); then
-			local names var
-			fresh
-			var=$last_var
-			for names in $lift_vars[__unified__]; do
-				for name in $=names; do
-					if (($+lift[$name])); then
-						unify $var $name
-					fi
-					if (($+lift_vars[$name])); then
-						setvar $var $lift_vars[$name]
-					fi
-				done
-			done
-		fi
-		local inner outer
 		for inner outer in ${(kv)lift}; do
 			((${+lift_vars[$inner]})) || \
 				die "variable ${(qqq)inner} not set, was requested by caller as ${(qqq)outer}"
-			setvar $outer ${lift_vars[$inner]}
+			vars[$outer]=${lift_vars[$inner]}
 		done
 	fi
 }
 
-parse-previous() {
-	typeset -g previous_parsed has_previous
-	typeset -gA previous
-	local arg
-
-	(($previous_parsed)) && return
-
-	if ! [[ -f $FILE ]]; then
-		info "changed: missing $FILE"
-		previous_parsed=1
-		has_previous=0
-		return 1
-	fi
-
-	for arg in "${(s::Q)$(<$FILE)}"; do
-		if [[ "$arg" != *=* ]]; then
-			die "$0: Malformed argument: ${(qqq)arg}"
-		fi
-		if (( $+previous[${arg%%=*}] )); then
-			die "$0: Duplicate argument: ${arg%%=*}"
-		fi
-		previous[${arg%%=*}]=${arg#*=}
-	done
-
-	previous_parsed=1
-	has_previous=1
-}
-
 if (($+functions[main])); then
 	redo-ifchange $0:h:a/common.zsh || exit $?
 	autoload_functions
 	decode_args
-	start_info
+	start-info
 	dep_add_file $DO
 	dep_add_file common.zsh
 	parse-previous
 	if (($+previous[__check_deps__])) && execlineb -c $previous[__check_deps__]; then
-		exit_unchanged
+		exit-unchanged
 	fi
 	main || exit $?
 	finish