fixup

1 files changed, 31 insertions, 23 deletions

diff --git a/ev b/ev
index 9b35b50..c418ed5 100755
--- a/ev
+++ b/ev
@@ -1,17 +1,19 @@
 #!/usr/bin/env awk -f
 
-# an evaluator of code
+# an evaluator of code: scanner, parser and bytecode vm.
 
 BEGIN {
-	# prec array contains the precedence order of operators
-	prec["="] = 1
+	# The prec array contains the precedence level of binary operators.
+	prec["="] = prec["=="] = prec["!="] = prec["<"] = prec["<="] = prec[">"] = prec[">="] = 1
+	prec["+="] = prec["-="] = prec["*="] = prec["/="] = prec["%="] = prec["^="] = 1
 	prec["+"] = prec["-"] = 2
-	prec["*"] = prec["/"] = 3
+	prec["*"] = prec["/"] =  prec["%"] = 3
 	prec["^"] = 4
-	# rigth array contains operators which are right associative
-	right["="] = right["^"] = 1
+	# The rigth array contains binary operators which are right associative.
+	right["="] = right["+="] = right["-="] = right["*="] = right["/="] = right["%="] = right["^="] = 1
+	right["^"] = 1
 
-	pc = 0
+	ml = pc = 0
 	split("", code)
 	split("", mem)
 	split("", var)
@@ -27,15 +29,17 @@ BEGIN {
 function scan() {
 	ptok = tok
 	sub(/^[ \t]+/, "", line)
-	if (match(line, /^[0-9]([.0-9]*(e[+-]*)*[0-9])*/)) {
+	if (match(line, /^[0-9]([.0-9]*(e[+-]*)*[0-9])*/)) {           # Literal number
 		tok = "d" substr(line, 1, RLENGTH)
-	} else if (match(line, /^([][}{)(,+-=?:]|[*\/÷\^])/)) {
+	} else if (match(line, /^([-=+|&]{2}|![=~]|[<>+-*\/^%]=)/)) {  # Operator (2 chars)
 		tok = substr(line, 1, RLENGTH)
-	} else if (match(line, /^[A-Za-z_][A-Za-z_0-9]*/)) {
+	} 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)
-	} else if (match(line, /^"(\\.|[^\\"])*"/)) {
+	} else if (match(line, /^"(\\.|[^\\"])*"/)) {                  # Literal string
 		tok = "s" substr(line, 2, RLENGTH-2)
-	} else {
+	} else {                                                       # Bad token
 		tok = "b" substr(line, 1, 1)
 	}
 	line = substr(line, RLENGTH+1)
@@ -43,8 +47,8 @@ function scan() {
 }
 
 # TODO: unary operators
-function parse(   stack, sl, i) {
-	i = length(code)
+function parse(   stack, sl, i, b) {
+	b = i = length(code)
 	while (scan() > 0) {
 		if (tok == "(") {
 			stack[++sl] = tok
@@ -52,7 +56,8 @@ function parse(   stack, sl, i) {
 			while (sl && stack[sl] != "(") code[i++] = stack[sl--]
 			sl--
 		} else if (tok in prec) {
-			if (tok == "=" && ptok ~ /^v/) sub(/^v/, "p", code[i-1])  # mutate var to pointer for assign
+			# print "tok:" tok " ptok:" ptok  
+			if (tok ~ /[+-*\/%^]?=/ && ptok ~ /^v/) sub(/^v/, "p", code[i-1])  # hack: mutate var to pointer for assign
 			# Test precedence against stack, or associativity if same precedence
 			while (sl && (prec[tok] < prec[stack[sl]] || prec[tok] == prec[stack[sl]] && !(stack[sl] in right))) {
 				code[i++] = stack[sl--]
@@ -63,13 +68,12 @@ function parse(   stack, sl, i) {
 		}
 	}
 	while (sl) code[i++] = stack[sl--]
-	# for (j = 0; j < i; j++) printf("%s ", code[j]); print ""
+	for (j = b; j < i; j++) printf("%s ", code[j]); print ""
 }
 
 # TODO: if, while, function
 function run(   c, i, l, t) {
 	cl = length(code)
-	ml = length(mem)
 	while (pc < cl) {
 		c = code[pc]
 		if (c == "+") {
@@ -83,20 +87,24 @@ function run(   c, i, l, t) {
 		} else if (c == "^") {
 			mem[--ml] = mem[ml-1] ^ mem[ml]
 		} else if (c == "=") {
-			var[substr(mem[ml-1], 2)] = mem[ml]
-			mem[--ml] = mem[ml]
+			mem[--ml] = var[substr(mem[ml-1], 2)] = mem[ml]
+		} else if (c == "+=") {
+			mem[--ml] = var[substr(mem[ml-1], 2)] += mem[ml]
 		} else if (c ~ /^p/) {
 			mem[++ml] =  c
 		} else if (c ~ /^v/) {
 			mem[++ml] =  var[substr(c, 2)]
 		} else if (c ~ /^[d]/) {
 			mem[++ml] =  0 + substr(c, 2)
+		} else {
+			print "run: invalid instruction " c
+			return
 		}
-		printf "c" pc ": " c; for (i = 1; i <= ml; i++) printf ", " i ":" mem[i]; print ""
-		for (i in var) print "var[" i "]=" var[i]
+		# printf "c" pc ":%s", c; for (i = 1; i <= ml; i++) printf " " i ":" mem[i]; print ""
+		# for (i in var) print "var[" i "]=" var[i]
 		pc++
 	}
-	print mem[ml]
-	var["_"] = mem[ml--]
+	print var["_"] = mem[ml--]
+	print "ml: " ml ", len(mem): " length(mem)
 	# for (i = ml; j in mem; i++) delete mem[i]
 }