updateHEADmain

1 files changed, 54 insertions, 19 deletions

diff --git a/ev b/ev
index 7fcf207..534368a 100755
--- a/ev
+++ b/ev
@@ -12,7 +12,12 @@ BEGIN {
 	# The rigth array contains binary operators which are right associative.
 	right["="] = right["+="] = right["-="] = right["*="] = right["/="] = right["%="] = right["^="] = 1
 	right["^"] = 1
+	start[")"] = "("; end["("] = ")"
+	start["}"] = "{"; end["{"] = "}"
+	start["]"] = "["; end["["] = "]"
 
+
+	cl = 0
 	sp = pc = 0      # sp: stack pointer, pc: program counter.
 	split("", code)
 	split("", stack)
@@ -21,19 +26,18 @@ BEGIN {
 }
 {
 	line = $0
-	parse()
-	run()
+	while (parse()) run()
 	printf "> "
 }
 
-function scan() {
+function scan(peek) {
 	ptok = tok
 	sub(/^[ \t]+/, "", line)
 	if (match(line, /^[0-9]([.0-9]*(e[+-]*)*[0-9])*/)) {           # Literal number
 		tok = "d" substr(line, 1, RLENGTH)
 	} else if (match(line, /^([-=+|&]{2}|![=~]|[<>+-*\/^%]=)/)) {  # Operator (2 chars)
 		tok = substr(line, 1, RLENGTH)
-	} else if (match(line, /^([][}{)(,+-=?:]|[*\/÷\^])/)) {        # Operator (1 char)
+	} else if (match(line, /^([][}{)(,+-=?:;]|[*\/÷\^])/)) {       # Operator (1 char)
 		tok = substr(line, 1, RLENGTH)
 	} else if (match(line, /^[A-Za-z_][A-Za-z_0-9]*/)) {           # Identifier
 		tok = "v" substr(line, 1, RLENGTH)
@@ -42,39 +46,66 @@ function scan() {
 	} else {                                                       # Bad token
 		tok = "b" substr(line, 1, 1)
 	}
-	line = substr(line, RLENGTH+1)
+	if (!peek) line = substr(line, RLENGTH+1)
 	return RLENGTH
 }
 
-# TODO: unary operators, flow contror
-function parse(   ops, sl, i, b) {
-	b = i = length(code)
+# TODO: unary operators, flow control, functions
+# Recursive descent parser
+function parse(want,   got, ops, sl, i, b) {
+	b = cl
 	while (scan() > 0) {
-		if (tok == "(") {
+		if (want && ! got) {
+			if ((got = tok) != want && want == "(") { print "missing " want; return 0 }
+			ops[++sl] = "done"
+		}
+		if (tok == ";") {
+			break
+		} else if (tok == "vif") {
+			if (! parse("(")) break
+			code[cl++] = "jzLif" ++lif
+			if (! parse("{")) break
+			if (scan(1) && tok == "velse") {
+				code[cl++] = "jLif" lif+1
+				code[cl++] = "Lif" lif
+				sym["Lif" lif] = cl
+				if (! parse("{")) break
+				sym["Lif" ++lif] = cl
+			} else {
+				code[cl++] = "Lif" lif
+				sym["Lif" lif] = cl
+			}
+		} else if (tok in end) {
 			ops[++sl] = tok
-		} else if (tok == ")") {
-			while (sl && ops[sl] != "(") code[i++] = ops[sl--]
-			sl--
+		} else if (tok in start) {
+			while (sl && ops[sl] != start[tok]) code[cl++] = ops[sl--]
+			if (ops[--sl] == "done") { sl--; break }
 		} else if (tok in prec) {
 		   # print "tok:" tok " ptok:" ptok
-		   if (tok ~ /[+-*\/%^]?=/ && ptok ~ /^v/) sub(/^v/, "p", code[i-1])  # mutate var to pointer for assign
+		   if (tok ~ /[+-*\/%^]?=/ && ptok ~ /^v/) sub(/^v/, "p", code[cl-1])
 		   # Test precedence against ops, or associativity if same precedence.
-		   while (sl && (prec[tok] < prec[ops[sl]] || prec[tok] == prec[ops[sl]] && !(ops[sl] in right))) {
-			   code[i++] = ops[sl--]
+		   while (sl && (prec[tok] < prec[ops[sl]] ||
+				  prec[tok] == prec[ops[sl]] && !(ops[sl] in right))) {
+			   code[cl++] = ops[sl--]
 		   }
 		   ops[++sl] = tok
 		} else {
-			code[i++] = tok
+			code[cl++] = tok
 		}
 	}
-	while (sl) code[i++] = ops[sl--]
-	for (j = b; j < i; j++) printf("%s ", code[j]); print ""
+	while (sl) {
+		# if (ops[sl] in end) { print "missing " end[ops[sl]]; return 0 }
+		if (want && ops[sl--] == "done") continue
+		code[cl++] = ops[sl--]
+	}
+	return cl-b
 }
 
 # TODO: if, while, function
 # Feel like being a stack machine.
 function run(   c, i, l, t) {
 	cl = length(code)
+	for (i = pc; i < cl; i++) printf("%s ", code[i]); print ""
 	while (pc < cl) {
 		c = code[pc]
 		if (c == "+") {
@@ -97,11 +128,15 @@ function run(   c, i, l, t) {
 			stack[++sp] =  sym[substr(c, 2)]
 		} else if (c ~ /^[d]/) {
 			stack[++sp] =  0 + substr(c, 2)
+		} else if (c ~ /^jz/) {
+			if (!stack[sp--]) { pc = sym[substr(c, 3)]; continue }
+		} else if (c ~ /^L/) {
+			# nop on label
 		} else {
 			print "run: invalid instruction " c
 			return
 		}
-		# printf "c" pc ":%s", c; for (i = 1; i <= sp; i++) printf " " i ":" stack[i]; print ""
+		printf "c" pc ":%s", c; for (i = 1; i <= sp; i++) printf " " i ":" stack[i]; print ""
 		# for (i in sym) print "sym[" i "]=" sym[i]
 		pc++
 	}