ev: implement assign

1 files changed, 29 insertions, 9 deletions

diff --git a/ev b/ev
index 4e33fb9..9b35b50 100755
--- a/ev
+++ b/ev
@@ -11,13 +11,21 @@ BEGIN {
 	# rigth array contains operators which are right associative
 	right["="] = right["^"] = 1
 
+	pc = 0
 	split("", code)
 	split("", mem)
+	split("", var)
+	printf "> "
+}
+{
+	line = $0
+	parse()
+	run()
 	printf "> "
 }
-{ line = $0; parse(); run(); printf "> " }
 
 function scan() {
+	ptok = tok
 	sub(/^[ \t]+/, "", line)
 	if (match(line, /^[0-9]([.0-9]*(e[+-]*)*[0-9])*/)) {
 		tok = "d" substr(line, 1, RLENGTH)
@@ -44,24 +52,26 @@ 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
 			# 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--]
 			}
 			stack[++sl] = tok
-		} else code[i++] = tok
+		} else {
+			code[i++] = tok
+		}
 	}
 	while (sl) code[i++] = stack[sl--]
 	# for (j = 0; j < i; j++) printf("%s ", code[j]); print ""
 }
 
-# TODO: assign, if, while, function
+# TODO: if, while, function
 function run(   c, i, l, t) {
 	cl = length(code)
 	ml = length(mem)
-	i = 0
-	while (i < cl) {
-		c = code[i]
+	while (pc < cl) {
+		c = code[pc]
 		if (c == "+") {
 			mem[--ml] = mem[ml-1] + mem[ml]
 		} else if (c == "-") {
@@ -72,11 +82,21 @@ function run(   c, i, l, t) {
 			mem[--ml] = mem[ml-1] / mem[ml]
 		} else if (c == "^") {
 			mem[--ml] = mem[ml-1] ^ mem[ml]
-		} else {
+		} else if (c == "=") {
+			var[substr(mem[ml-1], 2)] = mem[ml]
+			mem[--ml] = 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)
 		}
-		i++
+		printf "c" pc ": " 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]
-	# for (i = ml; i in mem; i++) delete mem[i]
+	var["_"] = mem[ml--]
+	# for (i = ml; j in mem; i++) delete mem[i]
 }