Add spec parser

Currently, the parser only supports definitions of lexical specification.

1 files changed, 32 insertions, 0 deletions

diff --git a/spec/syntax_error.go b/spec/syntax_error.go
new file mode 100644
index 0000000..815b38f
--- /dev/null
+++ b/spec/syntax_error.go
@@ -0,0 +1,32 @@
+package spec
+
+import "fmt"
+
+type SyntaxError struct {
+	message string
+}
+
+func newSyntaxError(message string) *SyntaxError {
+	return &SyntaxError{
+		message: message,
+	}
+}
+
+func (e *SyntaxError) Error() string {
+	return fmt.Sprintf("syntax error: %s", e.message)
+}
+
+var (
+	// lexical errors
+	synErrUnclosedTerminal  = newSyntaxError("unclosed terminal")
+	synErrInvalidEscSeq     = newSyntaxError("invalid escape sequence")
+	synErrIncompletedEscSeq = newSyntaxError("incompleted escape sequence; unexpected EOF following \\")
+
+	// syntax errors
+	synErrInvalidToken     = newSyntaxError("invalid token")
+	synErrNoProduction     = newSyntaxError("a grammar must have at least one production")
+	synErrNoProductionName = newSyntaxError("a production name is missing")
+	synErrNoColon          = newSyntaxError("the colon must precede alternatives")
+	synErrNoSemicolon      = newSyntaxError("the semicolon is missing at the last of an alternative")
+	synErrNoElement        = newSyntaxError("an alternative must have at least one element")
+)