Snippets

YellowAfterlife Tiny Expression Runtime from "A small guide on writing interpreters" post

Updated by VadimD
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File txr.gml Added

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+#define txr_init
+#macro txr_error global.txr_error_val
+
+// parser:
+#macro txr_parse_tokens global.txr_parse_tokens_val
+txr_parse_tokens = ds_list_create();
+enum txr_token {
+	eof = 0, // <end of file>
+    op = 1, // + - * / % div
+    par_open = 2, // (
+    par_close = 3, // )
+    number = 4, // 37
+    ident = 5, // some
+}
+enum txr_op {
+    mul  = 0x01, // *
+    fdiv = 0x02, // /
+    fmod = 0x03, // %
+    idiv = 0x04, // div
+    add  = 0x10, // +
+    sub  = 0x11, // -
+	maxp = 0x20 // maximum priority
+}
+
+// builder:
+#macro txr_build_list global.txr_build_list_val
+#macro txr_build_node global.txr_build_node_val
+#macro txr_build_pos  global.txr_build_pos_val
+#macro txr_build_len  global.txr_build_len_val
+enum txr_node {
+	number = 1, // (number)
+	ident = 2, // (name)
+	unop = 3, // (unop, node)
+	binop = 4, // (binop, a, b)
+}
+enum txr_unop {
+	negate = 1, // -value
+}
+enum txr_build_flag {
+	no_ops = 1
+}
+
+// compiler:
+#macro txr_compile_list global.txr_compile_list_val
+txr_compile_list = ds_list_create();
+enum txr_action {
+	number = 1, // (value): push(value)
+	ident = 2, // (name): push(self[name])
+	unop = 3, // (unop): push(-pop())
+	binop = 4, // (op): a = pop(); b = pop(); push(binop(op, a, b))
+}
+
+#define txr_parse
+var str = argument0;
+var len = string_length(str);
+var out = txr_parse_tokens;
+ds_list_clear(out);
+var pos = 1;
+while (pos <= len) {
+    var start = pos;
+    var char = string_ord_at(str, pos);
+    pos += 1;
+    switch (char) {
+		case ord(" "): case ord("\t"): case ord("\r"): case ord("\n"): break;
+		case ord("("): ds_list_add(out, [txr_token.par_open, start]); break;
+		case ord(")"): ds_list_add(out, [txr_token.par_close, start]); break;
+        case ord("+"): ds_list_add(out, [txr_token.op, start, txr_op.add]); break;
+		case ord("-"): ds_list_add(out, [txr_token.op, start, txr_op.sub]); break;
+		case ord("*"): ds_list_add(out, [txr_token.op, start, txr_op.mul]); break;
+		case ord("/"): ds_list_add(out, [txr_token.op, start, txr_op.fdiv]); break;
+		case ord("%"): ds_list_add(out, [txr_token.op, start, txr_op.fmod]); break;
+		default:
+			if (char >= ord("0") && char <= ord("9")) {
+				while (pos <= len) {
+					char = string_ord_at(str, pos);
+					if (char >= ord("0") && char <= ord("9")) {
+						pos += 1;
+					} else break;
+				}
+				var val = real(string_copy(str, start, pos - start));
+				ds_list_add(out, [txr_token.number, start, val]);
+			}
+			else if (char == ord("_")
+				|| (char >= ord("a") && char <= ord("z"))
+				|| (char >= ord("A") && char <= ord("Z"))
+			) {
+				while (pos <= len) {
+					char = string_ord_at(str, pos);
+					if (char == ord("_")
+						|| (char >= ord("0") && char <= ord("9"))
+						|| (char >= ord("a") && char <= ord("z"))
+						|| (char >= ord("A") && char <= ord("Z"))
+					) {
+						pos += 1;
+					} else break;
+				}
+				var name = string_copy(str, start, pos - start);
+				switch (name) {
+					case "mod": ds_list_add(out, [txr_token.op, start, txr_op.fmod]); break;
+					case "div": ds_list_add(out, [txr_token.op, start, txr_op.idiv]); break;
+					default: ds_list_add(out, [txr_token.ident, start, name]); break;
+				}
+			}
+			else {
+				ds_list_clear(out);
+				return txr_throw("Unexpected character `" + chr(char) + "`", start);
+			}
+    }
+}
+ds_list_add(out, [txr_token.eof, len + 1]);
+return false;
+
+#define txr_throw
+/// @desc txr_throw(error_text, position)
+/// @param error_text
+/// @param position
+txr_error = argument0 + " at position " + string(argument1);
+return true;
+
+#define txr_build
+txr_build_list = txr_parse_tokens;
+txr_build_pos = 0;
+txr_build_len = ds_list_size(txr_build_list);
+if (txr_build_expr(0)) return true;
+if (txr_build_pos < txr_build_len - 1) {
+	return txr_throw_at("Trailing data", txr_parse_tokens[|txr_build_pos]);
+} else return false;
+
+#define txr_build_expr
+/// @param flags
+var flags = argument0;
+var tk = txr_build_list[|txr_build_pos++];
+switch (tk[0]) {
+	case txr_token.number: txr_build_node = [txr_node.number, tk[1], tk[2]]; break;
+	case txr_token.ident: txr_build_node = [txr_node.ident, tk[1], tk[2]]; break;
+	case txr_token.par_open: // (value)
+		if (txr_build_expr(0)) return true;
+		tk = txr_build_list[|txr_build_pos++];
+		if (tk[0] != txr_token.par_close) return txr_throw_at("Expected a `)`", tk);
+		break;
+	case txr_token.op: // -value, +value
+		switch (tk[2]) {
+			case txr_op.add:
+				if (txr_build_expr(txr_build_flag.no_ops)) return true;
+				break;
+			case txr_op.sub:
+				if (txr_build_expr(txr_build_flag.no_ops)) return true;
+				txr_build_node = [txr_node.unop, tk[1], txr_unop.negate, txr_build_node];
+				break;
+			default: return txr_throw_at("Unexpected token", tk);
+		}
+		break;
+	default: return txr_throw_at("Unexpected token", tk);
+}
+if ((flags & txr_build_flag.no_ops) == 0) {
+	tk = txr_build_list[|txr_build_pos];
+	if (tk[0] == txr_token.op) {
+		txr_build_pos += 1;
+		if (txr_build_ops(tk)) return true;
+	}
+}
+return false;
+
+#define txr_build_ops
+/// @param first
+var nodes = ds_list_create();
+ds_list_add(nodes, txr_build_node);
+var ops = ds_list_create();
+ds_list_add(ops, argument0);
+//
+var tk;
+while (1) {
+	// try to read the next expression and add it to list:
+	if (txr_build_expr(txr_build_flag.no_ops)) {
+		ds_list_destroy(nodes);
+		ds_list_destroy(ops);
+		return true;
+	}
+	ds_list_add(nodes, txr_build_node);
+	// if followed by an operator, add that too, stop otherwise:
+	tk = txr_build_list[|txr_build_pos];
+	if (tk[0] == txr_token.op) {
+		txr_build_pos++;
+		ds_list_add(ops, tk);
+	} else break;
+}
+// Nest operators from top to bottom priority:
+var n = ds_list_size(ops);
+var pmax = (txr_op.maxp >> 4);
+var pri = 0;
+while (pri < pmax) {
+	for (var i = 0; i < n; i++) {
+		tk = ops[|i];
+		if ((tk[2] >> 4) != pri) continue;
+		nodes[|i] = [txr_node.binop, tk[1], tk[2], nodes[|i], nodes[|i + 1]];
+		ds_list_delete(nodes, i + 1);
+		ds_list_delete(ops, i);
+		n -= 1; i -= 1;
+	}
+	pri += 1;
+}
+// Cleanup and return:
+txr_build_node = nodes[|0];
+ds_list_destroy(nodes);
+ds_list_destroy(ops);
+return false;
+
+#define txr_throw_at
+/// @param error_text
+/// @param token
+var tk = argument1;
+if (tk[0] == txr_token.eof) {
+	return txr_throw(argument0, "<EOF>");
+} else return txr_throw(argument0, tk[1]);
+
+#define txr_compile_expr
+/// @param node
+var q = argument0;
+var out = txr_compile_list;
+switch (q[0]) {
+	case txr_node.number: ds_list_add(out, [txr_action.number, q[1], q[2]]); break;
+	case txr_node.ident: ds_list_add(out, [txr_action.ident, q[1], q[2]]); break;
+	case txr_node.unop:
+		if (txr_compile_expr(q[3])) return true;
+		ds_list_add(out, [txr_action.unop, q[1], q[2]]);
+		break;
+	case txr_node.binop:
+		if (txr_compile_expr(q[3])) return true;
+		if (txr_compile_expr(q[4])) return true;
+		ds_list_add(out, [txr_action.binop, q[1], q[2]]);
+		break;
+	default: return txr_throw_at("Cannot compile node type " + string(q[0]), q);
+}
+return false;
+
+#define txr_compile
+if (txr_parse(argument0)) return undefined;
+if (txr_build()) return undefined;
+var out = txr_compile_list;
+ds_list_clear(out);
+if (txr_compile_expr(txr_build_node)) return undefined;
+var n = ds_list_size(out);
+var arr = array_create(n);
+for (var i = 0; i < n; i++) arr[i] = out[|i];
+ds_list_clear(out);
+return arr;
+
+#define txr_exec
+/// @param actions
+var arr = argument0;
+var len = array_length_1d(arr);
+var pos = 0;
+var stack = ds_stack_create();
+while (pos < len) {
+	var q = arr[pos++];
+	switch (q[0]) {
+		case txr_action.number: ds_stack_push(stack, q[2]); break;
+		case txr_action.unop: ds_stack_push(stack, -ds_stack_pop(stack)); break;
+		case txr_action.binop:
+			var b = ds_stack_pop(stack);
+			var a = ds_stack_pop(stack);
+			switch (q[2]) {
+				case txr_op.add: a += b; break;
+				case txr_op.sub: a -= b; break;
+				case txr_op.mul: a *= b; break;
+				case txr_op.fdiv: a /= b; break;
+				case txr_op.fmod: if (b != 0) a %= b; else a = 0; break;
+				case txr_op.idiv: if (b != 0) a = a div b; else a = 0; break;
+				default: return txr_exec_exit("Can't apply operator " + string(q[2]), q, stack);
+			}
+			ds_stack_push(stack, a);
+			break;
+		case txr_action.ident:
+			var v = variable_instance_get(id, q[2]);
+			if (is_real(v) || is_int64(v) || is_bool(v)) {
+				ds_stack_push(stack, v);
+			} else return txr_exec_exit("Variable `" + q[2] + "` is not a number", q, stack);
+			break;
+		default: return txr_exec_exit("Can't run action " + string(q[0]), q, stack);
+	}
+}
+var r = ds_stack_pop(stack);
+ds_stack_destroy(stack);
+txr_error = "";
+return r;
+
+#define txr_exec_exit
+/// @param error_text
+/// @param action
+/// @param stack
+ds_stack_destroy(argument2);
+return txr_throw(argument0, argument1[1]);

File txr.hx Deleted

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-#define txr_init
-#macro txr_error global.txr_error_val
-
-// parser:
-#macro txr_parse_tokens global.txr_parse_tokens_val
-txr_parse_tokens = ds_list_create();
-enum txr_token {
-	eof = 0, // <end of file>
-    op = 1, // + - * / % div
-    par_open = 2, // (
-    par_close = 3, // )
-    number = 4, // 37
-    ident = 5, // some
-}
-enum txr_op {
-    mul  = 0x01, // *
-    fdiv = 0x02, // /
-    fmod = 0x03, // %
-    idiv = 0x04, // div
-    add  = 0x10, // +
-    sub  = 0x11, // -
-	maxp = 0x20 // maximum priority
-}
-
-// builder:
-#macro txr_build_list global.txr_build_list_val
-#macro txr_build_node global.txr_build_node_val
-#macro txr_build_pos  global.txr_build_pos_val
-#macro txr_build_len  global.txr_build_len_val
-enum txr_node {
-	number = 1, // (number)
-	ident = 2, // (name)
-	unop = 3, // (unop, node)
-	binop = 4, // (binop, a, b)
-}
-enum txr_unop {
-	negate = 1, // -value
-}
-enum txr_build_flag {
-	no_ops = 1
-}
-
-// compiler:
-#macro txr_compile_list global.txr_compile_list_val
-txr_compile_list = ds_list_create();
-enum txr_action {
-	number = 1, // (value): push(value)
-	ident = 2, // (name): push(self[name])
-	unop = 3, // (unop): push(-pop())
-	binop = 4, // (op): a = pop(); b = pop(); push(binop(op, a, b))
-}
-
-#define txr_parse
-var str = argument0;
-var len = string_length(str);
-var out = txr_parse_tokens;
-ds_list_clear(out);
-var pos = 1;
-while (pos <= len) {
-    var start = pos;
-    var char = string_ord_at(str, pos);
-    pos += 1;
-    switch (char) {
-		case ord(" "): case ord("\t"): case ord("\r"): case ord("\n"): break;
-		case ord("("): ds_list_add(out, [txr_token.par_open, start]); break;
-		case ord(")"): ds_list_add(out, [txr_token.par_close, start]); break;
-        case ord("+"): ds_list_add(out, [txr_token.op, start, txr_op.add]); break;
-		case ord("-"): ds_list_add(out, [txr_token.op, start, txr_op.sub]); break;
-		case ord("*"): ds_list_add(out, [txr_token.op, start, txr_op.mul]); break;
-		case ord("/"): ds_list_add(out, [txr_token.op, start, txr_op.fdiv]); break;
-		case ord("%"): ds_list_add(out, [txr_token.op, start, txr_op.fmod]); break;
-		default:
-			if (char >= ord("0") && char <= ord("9")) {
-				while (pos <= len) {
-					char = string_ord_at(str, pos);
-					if (char >= ord("0") && char <= ord("9")) {
-						pos += 1;
-					} else break;
-				}
-				var val = real(string_copy(str, start, pos - start));
-				ds_list_add(out, [txr_token.number, start, val]);
-			}
-			else if (char == ord("_")
-				|| (char >= ord("a") && char <= ord("z"))
-				|| (char >= ord("A") && char <= ord("Z"))
-			) {
-				while (pos <= len) {
-					char = string_ord_at(str, pos);
-					if (char == ord("_")
-						|| (char >= ord("0") && char <= ord("9"))
-						|| (char >= ord("a") && char <= ord("z"))
-						|| (char >= ord("A") && char <= ord("Z"))
-					) {
-						pos += 1;
-					} else break;
-				}
-				var name = string_copy(str, start, pos - start);
-				switch (name) {
-					case "mod": ds_list_add(out, [txr_token.op, start, txr_op.fmod]); break;
-					case "div": ds_list_add(out, [txr_token.op, start, txr_op.idiv]); break;
-					default: ds_list_add(out, [txr_token.ident, start, name]); break;
-				}
-			}
-			else {
-				ds_list_clear(out);
-				return txr_throw("Unexpected character `" + chr(char) + "`", start);
-			}
-    }
-}
-ds_list_add(out, [txr_token.eof, len + 1]);
-return false;
-
-#define txr_throw
-/// @desc txr_throw(error_text, position)
-/// @param error_text
-/// @param position
-txr_error = argument0 + " at position " + string(argument1);
-return true;
-
-#define txr_build
-txr_build_list = txr_parse_tokens;
-txr_build_pos = 0;
-txr_build_len = ds_list_size(txr_build_list);
-if (txr_build_expr(0)) return true;
-if (txr_build_pos < txr_build_len - 1) {
-	return txr_throw_at("Trailing data", txr_parse_tokens[|txr_build_pos]);
-} else return false;
-
-#define txr_build_expr
-/// @param flags
-var flags = argument0;
-var tk = txr_build_list[|txr_build_pos++];
-switch (tk[0]) {
-	case txr_token.number: txr_build_node = [txr_node.number, tk[1], tk[2]]; break;
-	case txr_token.ident: txr_build_node = [txr_node.ident, tk[1], tk[2]]; break;
-	case txr_token.par_open: // (value)
-		if (txr_build_expr(0)) return true;
-		tk = txr_build_list[|txr_build_pos++];
-		if (tk[0] != txr_token.par_close) return txr_throw_at("Expected a `)`", tk);
-		break;
-	case txr_token.op: // -value, +value
-		switch (tk[2]) {
-			case txr_op.add:
-				if (txr_build_expr(txr_build_flag.no_ops)) return true;
-				break;
-			case txr_op.sub:
-				if (txr_build_expr(txr_build_flag.no_ops)) return true;
-				txr_build_node = [txr_node.unop, tk[1], txr_unop.negate, txr_build_node];
-				break;
-			default: return txr_throw_at("Unexpected token", tk);
-		}
-		break;
-	default: return txr_throw_at("Unexpected token", tk);
-}
-if ((flags & txr_build_flag.no_ops) == 0) {
-	tk = txr_build_list[|txr_build_pos];
-	if (tk[0] == txr_token.op) {
-		txr_build_pos += 1;
-		if (txr_build_ops(tk)) return true;
-	}
-}
-return false;
-
-#define txr_build_ops
-/// @param first
-var nodes = ds_list_create();
-ds_list_add(nodes, txr_build_node);
-var ops = ds_list_create();
-ds_list_add(ops, argument0);
-//
-var tk;
-while (1) {
-	// try to read the next expression and add it to list:
-	if (txr_build_expr(txr_build_flag.no_ops)) {
-		ds_list_destroy(nodes);
-		ds_list_destroy(ops);
-		return true;
-	}
-	ds_list_add(nodes, txr_build_node);
-	// if followed by an operator, add that too, stop otherwise:
-	tk = txr_build_list[|txr_build_pos];
-	if (tk[0] == txr_token.op) {
-		txr_build_pos++;
-		ds_list_add(ops, tk);
-	} else break;
-}
-// Nest operators from top to bottom priority:
-var n = ds_list_size(ops);
-var pmax = (txr_op.maxp >> 4);
-var pri = 0;
-while (pri < pmax) {
-	for (var i = 0; i < n; i++) {
-		tk = ops[|i];
-		if ((tk[2] >> 4) != pri) continue;
-		nodes[|i] = [txr_node.binop, tk[1], tk[2], nodes[|i], nodes[|i + 1]];
-		ds_list_delete(nodes, i + 1);
-		ds_list_delete(ops, i);
-		n -= 1; i -= 1;
-	}
-	pri += 1;
-}
-// Cleanup and return:
-txr_build_node = nodes[|0];
-ds_list_destroy(nodes);
-ds_list_destroy(ops);
-return false;
-
-#define txr_throw_at
-/// @param error_text
-/// @param token
-var tk = argument1;
-if (tk[0] == txr_token.eof) {
-	return txr_throw(argument0, "<EOF>");
-} else return txr_throw(argument0, tk[1]);
-
-#define txr_compile_expr
-/// @param node
-var q = argument0;
-var out = txr_compile_list;
-switch (q[0]) {
-	case txr_node.number: ds_list_add(out, [txr_action.number, q[1], q[2]]); break;
-	case txr_node.ident: ds_list_add(out, [txr_action.ident, q[1], q[2]]); break;
-	case txr_node.unop:
-		if (txr_compile_expr(q[3])) return true;
-		ds_list_add(out, [txr_action.unop, q[1], q[2]]);
-		break;
-	case txr_node.binop:
-		if (txr_compile_expr(q[3])) return true;
-		if (txr_compile_expr(q[4])) return true;
-		ds_list_add(out, [txr_action.binop, q[1], q[2]]);
-		break;
-	default: return txr_throw_at("Cannot compile node type " + string(q[0]), q);
-}
-return false;
-
-#define txr_compile
-if (txr_parse(argument0)) return undefined;
-if (txr_build()) return undefined;
-var out = txr_compile_list;
-ds_list_clear(out);
-if (txr_compile_expr(txr_build_node)) return undefined;
-var n = ds_list_size(out);
-var arr = array_create(n);
-for (var i = 0; i < n; i++) arr[i] = out[|i];
-ds_list_clear(out);
-return arr;
-
-#define txr_exec
-/// @param actions
-var arr = argument0;
-var len = array_length_1d(arr);
-var pos = 0;
-var stack = ds_stack_create();
-while (pos < len) {
-	var q = arr[pos++];
-	switch (q[0]) {
-		case txr_action.number: ds_stack_push(stack, q[2]); break;
-		case txr_action.unop: ds_stack_push(stack, -ds_stack_pop(stack)); break;
-		case txr_action.binop:
-			var b = ds_stack_pop(stack);
-			var a = ds_stack_pop(stack);
-			switch (q[2]) {
-				case txr_op.add: a += b; break;
-				case txr_op.sub: a -= b; break;
-				case txr_op.mul: a *= b; break;
-				case txr_op.fdiv: a /= b; break;
-				case txr_op.fmod: if (b != 0) a %= b; else a = 0; break;
-				case txr_op.idiv: if (b != 0) a = a div b; else a = 0; break;
-				default: return txr_exec_exit("Can't apply operator " + string(q[2]), q, stack);
-			}
-			ds_stack_push(stack, a);
-			break;
-		case txr_action.ident:
-			var v = variable_instance_get(id, q[2]);
-			if (is_real(v) || is_int64(v) || is_bool(v)) {
-				ds_stack_push(stack, v);
-			} else return txr_exec_exit("Variable `" + q[2] + "` is not a number", q, stack);
-			break;
-		default: return txr_exec_exit("Can't run action " + string(q[0]), q, stack);
-	}
-}
-var r = ds_stack_pop(stack);
-ds_stack_destroy(stack);
-txr_error = "";
-return r;
-
-#define txr_exec_exit
-/// @param error_text
-/// @param action
-/// @param stack
-ds_stack_destroy(argument2);
-return txr_throw(argument0, argument1[1]);
Created by VadimD
View revision

File txr.hx Added

  • Ignore whitespace
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+#define txr_init
+#macro txr_error global.txr_error_val
+
+// parser:
+#macro txr_parse_tokens global.txr_parse_tokens_val
+txr_parse_tokens = ds_list_create();
+enum txr_token {
+	eof = 0, // <end of file>
+    op = 1, // + - * / % div
+    par_open = 2, // (
+    par_close = 3, // )
+    number = 4, // 37
+    ident = 5, // some
+}
+enum txr_op {
+    mul  = 0x01, // *
+    fdiv = 0x02, // /
+    fmod = 0x03, // %
+    idiv = 0x04, // div
+    add  = 0x10, // +
+    sub  = 0x11, // -
+	maxp = 0x20 // maximum priority
+}
+
+// builder:
+#macro txr_build_list global.txr_build_list_val
+#macro txr_build_node global.txr_build_node_val
+#macro txr_build_pos  global.txr_build_pos_val
+#macro txr_build_len  global.txr_build_len_val
+enum txr_node {
+	number = 1, // (number)
+	ident = 2, // (name)
+	unop = 3, // (unop, node)
+	binop = 4, // (binop, a, b)
+}
+enum txr_unop {
+	negate = 1, // -value
+}
+enum txr_build_flag {
+	no_ops = 1
+}
+
+// compiler:
+#macro txr_compile_list global.txr_compile_list_val
+txr_compile_list = ds_list_create();
+enum txr_action {
+	number = 1, // (value): push(value)
+	ident = 2, // (name): push(self[name])
+	unop = 3, // (unop): push(-pop())
+	binop = 4, // (op): a = pop(); b = pop(); push(binop(op, a, b))
+}
+
+#define txr_parse
+var str = argument0;
+var len = string_length(str);
+var out = txr_parse_tokens;
+ds_list_clear(out);
+var pos = 1;
+while (pos <= len) {
+    var start = pos;
+    var char = string_ord_at(str, pos);
+    pos += 1;
+    switch (char) {
+		case ord(" "): case ord("\t"): case ord("\r"): case ord("\n"): break;
+		case ord("("): ds_list_add(out, [txr_token.par_open, start]); break;
+		case ord(")"): ds_list_add(out, [txr_token.par_close, start]); break;
+        case ord("+"): ds_list_add(out, [txr_token.op, start, txr_op.add]); break;
+		case ord("-"): ds_list_add(out, [txr_token.op, start, txr_op.sub]); break;
+		case ord("*"): ds_list_add(out, [txr_token.op, start, txr_op.mul]); break;
+		case ord("/"): ds_list_add(out, [txr_token.op, start, txr_op.fdiv]); break;
+		case ord("%"): ds_list_add(out, [txr_token.op, start, txr_op.fmod]); break;
+		default:
+			if (char >= ord("0") && char <= ord("9")) {
+				while (pos <= len) {
+					char = string_ord_at(str, pos);
+					if (char >= ord("0") && char <= ord("9")) {
+						pos += 1;
+					} else break;
+				}
+				var val = real(string_copy(str, start, pos - start));
+				ds_list_add(out, [txr_token.number, start, val]);
+			}
+			else if (char == ord("_")
+				|| (char >= ord("a") && char <= ord("z"))
+				|| (char >= ord("A") && char <= ord("Z"))
+			) {
+				while (pos <= len) {
+					char = string_ord_at(str, pos);
+					if (char == ord("_")
+						|| (char >= ord("0") && char <= ord("9"))
+						|| (char >= ord("a") && char <= ord("z"))
+						|| (char >= ord("A") && char <= ord("Z"))
+					) {
+						pos += 1;
+					} else break;
+				}
+				var name = string_copy(str, start, pos - start);
+				switch (name) {
+					case "mod": ds_list_add(out, [txr_token.op, start, txr_op.fmod]); break;
+					case "div": ds_list_add(out, [txr_token.op, start, txr_op.idiv]); break;
+					default: ds_list_add(out, [txr_token.ident, start, name]); break;
+				}
+			}
+			else {
+				ds_list_clear(out);
+				return txr_throw("Unexpected character `" + chr(char) + "`", start);
+			}
+    }
+}
+ds_list_add(out, [txr_token.eof, len + 1]);
+return false;
+
+#define txr_throw
+/// @desc txr_throw(error_text, position)
+/// @param error_text
+/// @param position
+txr_error = argument0 + " at position " + string(argument1);
+return true;
+
+#define txr_build
+txr_build_list = txr_parse_tokens;
+txr_build_pos = 0;
+txr_build_len = ds_list_size(txr_build_list);
+if (txr_build_expr(0)) return true;
+if (txr_build_pos < txr_build_len - 1) {
+	return txr_throw_at("Trailing data", txr_parse_tokens[|txr_build_pos]);
+} else return false;
+
+#define txr_build_expr
+/// @param flags
+var flags = argument0;
+var tk = txr_build_list[|txr_build_pos++];
+switch (tk[0]) {
+	case txr_token.number: txr_build_node = [txr_node.number, tk[1], tk[2]]; break;
+	case txr_token.ident: txr_build_node = [txr_node.ident, tk[1], tk[2]]; break;
+	case txr_token.par_open: // (value)
+		if (txr_build_expr(0)) return true;
+		tk = txr_build_list[|txr_build_pos++];
+		if (tk[0] != txr_token.par_close) return txr_throw_at("Expected a `)`", tk);
+		break;
+	case txr_token.op: // -value, +value
+		switch (tk[2]) {
+			case txr_op.add:
+				if (txr_build_expr(txr_build_flag.no_ops)) return true;
+				break;
+			case txr_op.sub:
+				if (txr_build_expr(txr_build_flag.no_ops)) return true;
+				txr_build_node = [txr_node.unop, tk[1], txr_unop.negate, txr_build_node];
+				break;
+			default: return txr_throw_at("Unexpected token", tk);
+		}
+		break;
+	default: return txr_throw_at("Unexpected token", tk);
+}
+if ((flags & txr_build_flag.no_ops) == 0) {
+	tk = txr_build_list[|txr_build_pos];
+	if (tk[0] == txr_token.op) {
+		txr_build_pos += 1;
+		if (txr_build_ops(tk)) return true;
+	}
+}
+return false;
+
+#define txr_build_ops
+/// @param first
+var nodes = ds_list_create();
+ds_list_add(nodes, txr_build_node);
+var ops = ds_list_create();
+ds_list_add(ops, argument0);
+//
+var tk;
+while (1) {
+	// try to read the next expression and add it to list:
+	if (txr_build_expr(txr_build_flag.no_ops)) {
+		ds_list_destroy(nodes);
+		ds_list_destroy(ops);
+		return true;
+	}
+	ds_list_add(nodes, txr_build_node);
+	// if followed by an operator, add that too, stop otherwise:
+	tk = txr_build_list[|txr_build_pos];
+	if (tk[0] == txr_token.op) {
+		txr_build_pos++;
+		ds_list_add(ops, tk);
+	} else break;
+}
+// Nest operators from top to bottom priority:
+var n = ds_list_size(ops);
+var pmax = (txr_op.maxp >> 4);
+var pri = 0;
+while (pri < pmax) {
+	for (var i = 0; i < n; i++) {
+		tk = ops[|i];
+		if ((tk[2] >> 4) != pri) continue;
+		nodes[|i] = [txr_node.binop, tk[1], tk[2], nodes[|i], nodes[|i + 1]];
+		ds_list_delete(nodes, i + 1);
+		ds_list_delete(ops, i);
+		n -= 1; i -= 1;
+	}
+	pri += 1;
+}
+// Cleanup and return:
+txr_build_node = nodes[|0];
+ds_list_destroy(nodes);
+ds_list_destroy(ops);
+return false;
+
+#define txr_throw_at
+/// @param error_text
+/// @param token
+var tk = argument1;
+if (tk[0] == txr_token.eof) {
+	return txr_throw(argument0, "<EOF>");
+} else return txr_throw(argument0, tk[1]);
+
+#define txr_compile_expr
+/// @param node
+var q = argument0;
+var out = txr_compile_list;
+switch (q[0]) {
+	case txr_node.number: ds_list_add(out, [txr_action.number, q[1], q[2]]); break;
+	case txr_node.ident: ds_list_add(out, [txr_action.ident, q[1], q[2]]); break;
+	case txr_node.unop:
+		if (txr_compile_expr(q[3])) return true;
+		ds_list_add(out, [txr_action.unop, q[1], q[2]]);
+		break;
+	case txr_node.binop:
+		if (txr_compile_expr(q[3])) return true;
+		if (txr_compile_expr(q[4])) return true;
+		ds_list_add(out, [txr_action.binop, q[1], q[2]]);
+		break;
+	default: return txr_throw_at("Cannot compile node type " + string(q[0]), q);
+}
+return false;
+
+#define txr_compile
+if (txr_parse(argument0)) return undefined;
+if (txr_build()) return undefined;
+var out = txr_compile_list;
+ds_list_clear(out);
+if (txr_compile_expr(txr_build_node)) return undefined;
+var n = ds_list_size(out);
+var arr = array_create(n);
+for (var i = 0; i < n; i++) arr[i] = out[|i];
+ds_list_clear(out);
+return arr;
+
+#define txr_exec
+/// @param actions
+var arr = argument0;
+var len = array_length_1d(arr);
+var pos = 0;
+var stack = ds_stack_create();
+while (pos < len) {
+	var q = arr[pos++];
+	switch (q[0]) {
+		case txr_action.number: ds_stack_push(stack, q[2]); break;
+		case txr_action.unop: ds_stack_push(stack, -ds_stack_pop(stack)); break;
+		case txr_action.binop:
+			var b = ds_stack_pop(stack);
+			var a = ds_stack_pop(stack);
+			switch (q[2]) {
+				case txr_op.add: a += b; break;
+				case txr_op.sub: a -= b; break;
+				case txr_op.mul: a *= b; break;
+				case txr_op.fdiv: a /= b; break;
+				case txr_op.fmod: if (b != 0) a %= b; else a = 0; break;
+				case txr_op.idiv: if (b != 0) a = a div b; else a = 0; break;
+				default: return txr_exec_exit("Can't apply operator " + string(q[2]), q, stack);
+			}
+			ds_stack_push(stack, a);
+			break;
+		case txr_action.ident:
+			var v = variable_instance_get(id, q[2]);
+			if (is_real(v) || is_int64(v) || is_bool(v)) {
+				ds_stack_push(stack, v);
+			} else return txr_exec_exit("Variable `" + q[2] + "` is not a number", q, stack);
+			break;
+		default: return txr_exec_exit("Can't run action " + string(q[0]), q, stack);
+	}
+}
+var r = ds_stack_pop(stack);
+ds_stack_destroy(stack);
+txr_error = "";
+return r;
+
+#define txr_exec_exit
+/// @param error_text
+/// @param action
+/// @param stack
+ds_stack_destroy(argument2);
+return txr_throw(argument0, argument1[1]);
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