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String concatenation now a thing.

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git-svn-id: https://svn.tlawal.org/svn/monkey@64 f6afcba9-9ef1-4bdd-9b72-7484f5705bac
This commit is contained in:
Tijani Lawal 2023-05-09 23:57:45 +00:00
parent ec6c1ce5aa
commit 64e048dfcd
2 changed files with 32 additions and 2 deletions
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14
evaluator/evaluator.go
View File

@ -86,7 +86,6 @@ func Eval(node ast.Node, env *object.Environment) object.Object {
}
return apply_function(function, args)
case *ast.StringLiteral:
return &object.String{Value: node.Value}
}
@ -232,6 +231,9 @@ func eval_infix_expression(operator string, left object.Object, right object.Obj
case left.Type() != right.Type():
return new_error("type mismatch: %s %s %s", left.Type(), operator, right.Type())
case left.Type() == object.STRING_OBJECT && right.Type() == object.STRING_OBJECT:
return eval_string_infix_expression(operator, left, right)
default:
return new_error("unknown operator: %s %s %s", left.Type(), operator, right.Type())
}
@ -287,6 +289,16 @@ func eval_if_expression(ie *ast.IfExpression, env *object.Environment) object.Ob
}
}
func eval_string_infix_expression(operator string, left, right object.Object) object.Object {
if operator != "+" {
return new_error("unknown operator: %s %s %s", left.Type(), operator, right.Type())
}
left_value := left.(*object.String).Value
right_value := right.(*object.String).Value
return &object.String{Value: left_value + right_value}
}
func is_truthy(object object.Object) bool {
switch object {
case NULL:

18
evaluator/evaluator_test.go
View File

@ -56,6 +56,10 @@ func TestErrorHandling(l_test *testing.T) {
}
`, "unknown operator: BOOLEAN + BOOLEAN"},
{"foobar", "identifier not found: foobar"},
{
`"Hello" - "World"`,
"unknown operator: STRING - STRING",
},
}
for _, tt := range tests {
@ -252,6 +256,20 @@ func TestStringLiteral(l_test *testing.T) {
}
}
func TestStringConcatenation(l_test *testing.T) {
input := `"Hello" + " " + "World!"`
evaluated := test_eval(input)
string, ok := evaluated.(*object.String)
if !ok {
l_test.Fatalf("object is not String. got=%T (%+v)", evaluated, evaluated)
}
if string.Value != "Hello World!" {
l_test.Errorf("String has wrong value. got=%q", string.Value)
}
}
// Helpers
func test_eval(input string) object.Object {
l_lexer := lexer.New(input)