ev: improve naming

1 files changed, 31 insertions, 30 deletions

diff --git a/ev b/ev
index c418ed5..7fcf207 100755
--- a/ev
+++ b/ev
@@ -13,10 +13,10 @@ BEGIN {
 	right["="] = right["+="] = right["-="] = right["*="] = right["/="] = right["%="] = right["^="] = 1
 	right["^"] = 1
 
-	ml = pc = 0
+	sp = pc = 0      # sp: stack pointer, pc: program counter.
 	split("", code)
-	split("", mem)
-	split("", var)
+	split("", stack)
+	split("", sym)
 	printf "> "
 }
 {
@@ -46,65 +46,66 @@ function scan() {
 	return RLENGTH
 }
 
-# TODO: unary operators
-function parse(   stack, sl, i, b) {
+# TODO: unary operators, flow contror
+function parse(   ops, sl, i, b) {
 	b = i = length(code)
 	while (scan() > 0) {
 		if (tok == "(") {
-			stack[++sl] = tok
+			ops[++sl] = tok
 		} else if (tok == ")") {
-			while (sl && stack[sl] != "(") code[i++] = stack[sl--]
+			while (sl && ops[sl] != "(") code[i++] = ops[sl--]
 			sl--
 		} else if (tok in prec) {
-			# 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--]
-			}
-			stack[++sl] = tok
+		   # print "tok:" tok " ptok:" ptok
+		   if (tok ~ /[+-*\/%^]?=/ && ptok ~ /^v/) sub(/^v/, "p", code[i-1])  # mutate var to pointer for assign
+		   # 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--]
+		   }
+		   ops[++sl] = tok
 		} else {
 			code[i++] = tok
 		}
 	}
-	while (sl) code[i++] = stack[sl--]
+	while (sl) code[i++] = ops[sl--]
 	for (j = b; j < i; j++) printf("%s ", code[j]); print ""
 }
 
 # TODO: if, while, function
+# Feel like being a stack machine.
 function run(   c, i, l, t) {
 	cl = length(code)
 	while (pc < cl) {
 		c = code[pc]
 		if (c == "+") {
-			mem[--ml] = mem[ml-1] + mem[ml]
+			stack[--sp] = stack[sp-1] + stack[sp]
 		} else if (c == "-") {
-			mem[--ml] = mem[ml-1] - mem[ml]
+			stack[--sp] = stack[sp-1] - stack[sp]
 		} else if (c == "*") {
-			mem[--ml] = mem[ml-1] * mem[ml]
+			stack[--sp] = stack[sp-1] * stack[sp]
 		} else if (c == "/") {
-			mem[--ml] = mem[ml-1] / mem[ml]
+			stack[--sp] = stack[sp-1] / stack[sp]
 		} else if (c == "^") {
-			mem[--ml] = mem[ml-1] ^ mem[ml]
+			stack[--sp] = stack[sp-1] ^ stack[sp]
 		} else if (c == "=") {
-			mem[--ml] = var[substr(mem[ml-1], 2)] = mem[ml]
+			stack[--sp] = sym[substr(stack[sp-1], 2)] = stack[sp]
 		} else if (c == "+=") {
-			mem[--ml] = var[substr(mem[ml-1], 2)] += mem[ml]
+			stack[--sp] = sym[substr(stack[sp-1], 2)] += stack[sp]
 		} else if (c ~ /^p/) {
-			mem[++ml] =  c
+			stack[++sp] =  c
 		} else if (c ~ /^v/) {
-			mem[++ml] =  var[substr(c, 2)]
+			stack[++sp] =  sym[substr(c, 2)]
 		} else if (c ~ /^[d]/) {
-			mem[++ml] =  0 + substr(c, 2)
+			stack[++sp] =  0 + substr(c, 2)
 		} else {
 			print "run: invalid instruction " c
 			return
 		}
-		# 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]
+		# 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++
 	}
-	print var["_"] = mem[ml--]
-	print "ml: " ml ", len(mem): " length(mem)
-	# for (i = ml; j in mem; i++) delete mem[i]
+	print sym["_"] = stack[sp--]
+	print "sp: " sp ", len(stack): " length(stack)
+	# for (i = sp; j in stack; i++) delete stack[i]
 }