builtin: implement array.pop()

vlib/builtin/array.v

@@ -256,6 +256,22 @@ pub fn (a array) last() voidptr {
 	}
 }
 
+// array.pop returns the last element of the array, and removes it
+pub fn (mut a array) pop() voidptr {
+	// in a sense, this is the opposite of `a << x`
+	$if !no_bounds_checking? {
+		if a.len == 0 {
+			panic('array.pop: array is empty')
+		}
+	}
+	new_len := a.len - 1
+	last_elem := unsafe { byteptr(a.data) + (new_len) * a.element_size }
+	a.len = new_len
+	// NB: a.cap is not changed here *on purpose*, so that
+	// further << ops on that array will be more efficient.
+	return memdup(last_elem, a.element_size)
+}
+
 // array.slice returns an array using the same buffer as original array
 // but starting from the `start` element and ending with the element before
 // the `end` element of the original array with the length and capacity

vlib/builtin/array_test.v

@@ -946,3 +946,29 @@ fn test_reverse_in_place() {
 	c.reverse_in_place()
 	assert c == [[5, 6], [3, 4], [1, 2]]
 }
+
+fn test_array_int_pop() {
+	mut a := [1,2,3,4,5]
+	assert a.len == 5
+	x := a.last()
+	y := a.pop()
+	assert x == y
+	assert a.len == 4
+	z := a.pop()
+	assert a.len == 3
+	assert z == 4
+	a.pop()
+	a.pop()
+	final := a.pop()
+	assert final == 1
+}
+
+fn test_array_string_pop() {
+	mut a := ['abc', 'def', 'xyz']
+	assert a.len == 3
+	assert a.pop() == 'xyz'
+	assert a.pop() == 'def'
+	assert a.pop() == 'abc'
+	assert a.len == 0
+	assert a.cap == 3
+}

vlib/v/checker/checker.v

@@ -859,10 +859,14 @@ pub fn (mut c Checker) call_method(mut call_expr ast.CallExpr) table.Type {
 		call_expr.return_type = left_type
 		call_expr.receiver_type = left_type.to_ptr()
 		return call_expr.return_type
-	} else if left_type_sym.kind == .array && method_name in ['first', 'last'] {
+	} else if left_type_sym.kind == .array && method_name in ['first', 'last', 'pop'] {
 		info := left_type_sym.info as table.Array
 		call_expr.return_type = info.elem_type
-		call_expr.receiver_type = left_type
+		if method_name == 'pop' {
+			call_expr.receiver_type = left_type.to_ptr()
+		} else {
+			call_expr.receiver_type = left_type
+		}
 		return call_expr.return_type
 	} else if left_type_sym.kind == .array && method_name in ['insert', 'prepend'] {
 		array_info := left_type_sym.info as table.Array

vlib/v/gen/fn.v

@@ -352,12 +352,12 @@ fn (mut g Gen) method_call(node ast.CallExpr) {
 	}
 	// TODO performance, detect `array` method differently
 	if left_sym.kind == .array && node.name in
-		['repeat', 'sort_with_compare', 'free', 'push_many', 'trim', 'first', 'last', 'clone', 'reverse', 'slice'] {
+		['repeat', 'sort_with_compare', 'free', 'push_many', 'trim', 'first', 'last', 'pop', 'clone', 'reverse', 'slice'] {
 		// && rec_sym.name == 'array' {
 		// && rec_sym.name == 'array' && receiver_name.starts_with('array') {
 		// `array_byte_clone` => `array_clone`
 		receiver_type_name = 'array'
-		if node.name in ['last', 'first'] {
+		if node.name in ['last', 'first', 'pop'] {
 			return_type_str := g.typ(node.return_type)
 			g.write('*($return_type_str*)')
 		}