style: no punctuation or capitalization in errors

internal/cli/arguments.go

@@ -24,9 +24,9 @@ func ParseOptions() (*Options, error) {
 
 	// Parse non-flag arguments.
 	if flag.NArg() == 0 {
-		return nil, fmt.Errorf("No input given.")
+		return nil, fmt.Errorf("no input given")
 	} else if flag.NArg() > 1 {
-		return nil, fmt.Errorf("More than 1 command-line argument.")
+		return nil, fmt.Errorf("more than 1 command-line argument")
 	}
 
 	return &Options{

internal/config/parse_from_args.go

@@ -14,9 +14,9 @@ func FromArgs() (*Config, error) {
 
 	// Parse non-flag arguments.
 	if flag.NArg() == 0 {
-		return nil, fmt.Errorf("No input given.")
+		return nil, fmt.Errorf("no input given")
 	} else if flag.NArg() > 1 {
-		return nil, fmt.Errorf("More than 1 command-line argument.")
+		return nil, fmt.Errorf("more than 1 command-line argument")
 	}
 
 	// Parse source type.

pkg/iterator/iterator.go

@@ -32,7 +32,7 @@ func (i Iterator[T]) Peek() (T, error) {
 	var null T
 
 	if i.IsDone() {
-		return null, fmt.Errorf("Iterator is exhausted.")
+		return null, fmt.Errorf("iterator is exhausted")
 	}
 
 	return i.data[i.index], nil

pkg/parser/parser.go

@@ -11,37 +11,37 @@ import (
 func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression, error) {
 	token, err := i.Next()
 	if err != nil {
-		return nil, fmt.Errorf("Could not get next token: %w", err)
+		return nil, fmt.Errorf("could not get next token: %w", err)
 	}
 
 	switch token.Type {
 	case tokenizer.TokenVariable:
 		return lambda.NewVariable(token.Value), nil
 	case tokenizer.TokenDot:
-		return nil, fmt.Errorf("Token '.' found without a corresponding slash (column %d).", token.Index)
+		return nil, fmt.Errorf("token '.' found without a corresponding slash (column %d)", token.Index)
 	case tokenizer.TokenSlash:
 		atoms := []string{}
 
 		for {
 			atom, atom_err := i.Next()
 			if atom_err != nil {
-				return nil, fmt.Errorf("Could not find parameter or terminator of function: %w", atom_err)
+				return nil, fmt.Errorf("could not find parameter or terminator of function: %w", atom_err)
 			} else if atom.Type == tokenizer.TokenVariable {
 				atoms = append(atoms, atom.Value)
 			} else if atom.Type == tokenizer.TokenDot {
 				break
 			} else {
-				return nil, fmt.Errorf("Expected function parameter or terminator, got '%v' (column %d).", atom.Value, atom.Index)
+				return nil, fmt.Errorf("expected function parameter or terminator, got '%v' (column %d)", atom.Value, atom.Index)
 			}
 		}
 
 		if len(atoms) == 0 {
-			return nil, fmt.Errorf("Every function must have atleast one parameter (column %d)", token.Index)
+			return nil, fmt.Errorf("every function must have atleast one parameter (column %d)", token.Index)
 		}
 
 		body, body_err := ParseExpression(i)
 		if body_err != nil {
-			return nil, fmt.Errorf("Could not parse function body: %w", body_err)
+			return nil, fmt.Errorf("could not parse function body: %w", body_err)
 		}
 
 		// Construction.
@@ -54,7 +54,7 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 	case tokenizer.TokenOpenParen:
 		fn, fn_err := ParseExpression(i)
 		if fn_err != nil {
-			return nil, fmt.Errorf("Could not parse call function: %w", fn_err)
+			return nil, fmt.Errorf("could not parse call function: %w", fn_err)
 		}
 
 		args := []lambda.Expression{}
@@ -66,7 +66,7 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 
 			arg, arg_err := ParseExpression(i)
 			if arg_err != nil {
-				return nil, fmt.Errorf("Could not parse call argument: %w", arg_err)
+				return nil, fmt.Errorf("could not parse call argument: %w", arg_err)
 			}
 
 			args = append(args, arg)
@@ -76,7 +76,7 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 		if close_err != nil {
 			return nil, fmt.Errorf("Could not parse call terminating parenthesis: %w", close_err)
 		} else if close.Type != tokenizer.TokenCloseParen {
-			return nil, fmt.Errorf("Expected call terminating parenthesis, got '%v' (column %v).", close.Value, close.Index)
+			return nil, fmt.Errorf("expected call terminating parenthesis, got '%v' (column %v)", close.Value, close.Index)
 		}
 
 		// Construction.
@@ -87,9 +87,9 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 
 		return result, nil
 	case tokenizer.TokenCloseParen:
-		return nil, fmt.Errorf("Token ')' found without a corresponding openning parenthesis (column %d).", token.Index)
+		return nil, fmt.Errorf("token ')' found without a corresponding openning parenthesis (column %d)", token.Index)
 	default:
-		return nil, fmt.Errorf("Unknown token '%v' (column %d).", token.Value, token.Index)
+		return nil, fmt.Errorf("unknown token '%v' (column %d)", token.Value, token.Index)
 	}
 }