Allow the use of local variables in expressions

4 files changed, 57 insertions, 2 deletions

diff --git a/GRAMMAR.txt b/GRAMMAR.txt
index bd7b4d4..68177fc 100644
--- a/GRAMMAR.txt
+++ b/GRAMMAR.txt
@@ -26,10 +26,11 @@ term -> numeral ( ( "<<" | ">>" ) numeral )*
 numeral -> factor ( ( "+" | "-" ) factor )*
 factor -> unary ( ( "*" | "/" ) unary )*
 unary -> ( "-" | "!" | "~" )? primary
-primary -> grouping | literal | call
+primary -> grouping | literal | call | variable
 grouping -> "(" expression ")"
 literal -> string | number
 string -> STRING*
 number -> NUMBER IDENTIFIER
 call -> IDENTIFIER "(" arg? ")"
 arg -> expression ( "," arg )?
+variable -> IDENTIFIER
diff --git a/expression.go b/expression.go
index 285cac3..9752730 100644
--- a/expression.go
+++ b/expression.go
@@ -323,3 +323,16 @@ type argument struct {
 	value exprExpr
 	next  *argument
 }
+
+type varExpr struct {
+	name string
+	ln   int
+}
+
+func (v *varExpr) markExpr() {}
+
+func (v *varExpr) markExprExpr() {}
+
+func (v *varExpr) markPrimaryExpr() {}
+
+func (v *varExpr) line() int { return v.ln }
diff --git a/generate.go b/generate.go
index 187ec8f..5701cb1 100644
--- a/generate.go
+++ b/generate.go
@@ -476,3 +476,18 @@ func (c *callExpr) generate(w io.Writer) (string, error) {
 
 	return ret, nil
 }
+
+func (v *varExpr) generate(w io.Writer) (string, error) {
+	ok, mutable := isDeclared(v.name, false)
+	if !ok {
+		return "", errUndeclared{name: v.name, line: v.line()}
+	}
+
+	if mutable {
+		reg := allocReg()
+		fmt.Fprintf(w, "%s =w loadl %%%s\n", reg, v.name)
+		return reg, nil
+	}
+
+	return localConsts[currentFunc][v.name], nil
+}
diff --git a/parse.go b/parse.go
index 7b4469e..c6b21f0 100644
--- a/parse.go
+++ b/parse.go
@@ -801,6 +801,14 @@ func parsePrimary(toks *tokens) (primaryExpr, error) {
 		return call, nil
 	}
 
+	variable, err := parseVariable(toks)
+	if err != nil {
+		return nil, err
+	}
+	if variable != nil {
+		return variable, nil
+	}
+
 	return nil, expectedPrimary{got: toks.current()}
 }
 
@@ -923,9 +931,14 @@ func parseCall(toks *tokens) (*callExpr, error) {
 		return nil, nil
 	}
 
-	if err := toks.mustMatch(lparen); err != nil {
+	ok, err := toks.match(lparen)
+	if err != nil {
 		return nil, err
 	}
+	if !ok {
+		toks.unreadTokens(2)
+		return nil, nil
+	}
 
 	args, err := parseArg(toks)
 	if err != nil {
@@ -970,3 +983,16 @@ func parseArg(toks *tokens) (*argument, error) {
 
 	return &argument{value: arg, next: next}, nil
 }
+
+func parseVariable(toks *tokens) (*varExpr, error) {
+	nameTok, ok := toks.consumeToken()
+	if !ok {
+		return nil, unexpectedEOF
+	}
+	if nameTok.kind != identifier {
+		toks.unreadToken()
+		return nil, nil
+	}
+
+	return &varExpr{name: nameTok.value, ln: nameTok.line}, nil
+}