Implement elseif

ast/ast_test.go

@@ -33,8 +33,8 @@ func TestString(t *testing.T) {
 			"foreach i, e in [1, 2, 3] \n  puts(i)\nend",
 		},
 		{
-			"if (true)\n  return (true)\nelse\n  puts(false)\nend",
-			"if (true)\n  return (true)\nelse\n  puts(false)\nend",
+			"if (true)\n  return (true)\nelif (true)\n  return (true)\nelse\n  puts(false)\nend",
+			"if (true)\n  return (true)\nelif (true)\n  return (true)\nelse\n  puts(false)\nend",
 		},
 		{
 			"while (true)\n  puts(true)\nend",

ast/if.go

@@ -6,10 +6,14 @@ import (
 	"github.com/flipez/rocket-lang/token"
 )
 
-type If struct {
-	Token       token.Token // the if token
+type ConditionConsequencePair struct {
 	Condition   Expression
 	Consequence *Block
+}
+
+type If struct {
+	Token       token.Token // the if token
+	ConConPairs []ConditionConsequencePair
 	Alternative *Block
 }
 
@@ -18,9 +22,16 @@ func (ie *If) String() string {
 	var out bytes.Buffer
 
 	out.WriteString("if (")
-	out.WriteString(ie.Condition.String())
+	out.WriteString(ie.ConConPairs[0].Condition.String())
 	out.WriteString(")\n  ")
-	out.WriteString(ie.Consequence.String())
+	out.WriteString(ie.ConConPairs[0].Consequence.String())
+
+	for _, pair := range ie.ConConPairs[1:] {
+		out.WriteString("\nelif (")
+		out.WriteString(pair.Condition.String())
+		out.WriteString(")\n  ")
+		out.WriteString(pair.Consequence.String())
+	}
 
 	if ie.Alternative != nil {
 		out.WriteString("\nelse\n  ")

docs/docs/control_expressions/if.md

@@ -1,19 +1,29 @@
 ---
-title: "If"
+title: "If / elif / else"
 menu:
   docs:
     parent: "controls"
 ---
+import CodeBlockSimple from '@site/components/CodeBlockSimple'
+
 # If
 With `if` and `else` keywords the flow of a program can be controlled.
 
-```js
-🚀 > if (a.type() == "STRING")
-  puts("is a string")
+<CodeBlockSimple input='a="test"
+if (a.type() == "STRING")
+puts("is a string")
 else
-  puts("is not a string")
-end
+puts("is not a string")
+end' output='is a string' />
+
+# Elif
+`elif` allows providing of an additional consequence check  after `if` and before evaluating the alternative provided by `else`. There is no limit on how many `elif` statements can be used.
 
-// which prints
-is a string
-```
+<CodeBlockSimple input='a = "test"
+if (a.type() == "BOOLEAN")
+puts("is a boolean")
+elif (a.type() == "STRING")
+puts("is a string")
+else
+puts("i have no idea")
+end' output='is a string' />

evaluator/if.go

@@ -6,16 +6,17 @@ import (
 )
 
 func evalIf(ie *ast.If, env *object.Environment) object.Object {
-	condition := Eval(ie.Condition, env)
-
-	if object.IsError(condition) {
-		return condition
+	for _, pair := range ie.ConConPairs {
+		condition := Eval(pair.Condition, env)
+		if object.IsError(condition) {
+			return condition
+		}
+		if object.IsTruthy(condition) {
+			return Eval(pair.Consequence, env)
+		}
 	}
-	if object.IsTruthy(condition) {
-		return Eval(ie.Consequence, env)
-	} else if ie.Alternative != nil {
+	if ie.Alternative != nil {
 		return Eval(ie.Alternative, env)
-	} else {
-		return object.NIL
 	}
+	return object.NIL
 }

parser/block.go

@@ -11,7 +11,8 @@ func (p *Parser) parseBlock() *ast.Block {
 
 	p.nextToken()
 
-	for !p.curTokenIs(token.RBRACE) && !p.curTokenIs(token.EOF) && !p.curTokenIs(token.END) && !p.curTokenIs(token.ELSE) && !p.curTokenIs(token.RESCUE) {
+	for !p.curTokenIs(token.RBRACE) && !p.curTokenIs(token.EOF) && !p.curTokenIs(token.END) && !p.curTokenIs(token.ELSE) && !p.curTokenIs(token.ELIF) && !p.curTokenIs(token.RESCUE) {
+
 		stmt := p.parseStatement()
 		if stmt != nil {
 			block.Statements = append(block.Statements, stmt)

parser/if.go

@@ -6,23 +6,41 @@ import (
 )
 
 func (p *Parser) parseIf() ast.Expression {
-	expression := &ast.If{Token: p.curToken}
+	expression := &ast.If{Token: p.curToken, ConConPairs: make([]ast.ConditionConsequencePair, 1)}
 	if !p.expectPeek(token.LPAREN) {
 		return nil
 	}
 
 	p.nextToken()
-	expression.Condition = p.parseExpression(LOWEST)
+	expression.ConConPairs[0].Condition = p.parseExpression(LOWEST)
 
 	if !p.expectPeek(token.RPAREN) {
 		return nil
 	}
 
-	expression.Consequence = p.parseBlock()
+	expression.ConConPairs[0].Consequence = p.parseBlock()
 
-	if p.curTokenIs(token.ELSE) {
+	for p.curTokenIs(token.ELIF) {
+
+		if !p.expectPeek(token.LPAREN) {
+			return nil
+		}
+		p.nextToken()
+
+		var pair ast.ConditionConsequencePair
+		pair.Condition = p.parseExpression(LOWEST)
+
+		if !p.expectPeek(token.RPAREN) {
+			return nil
+		}
 
+		pair.Consequence = p.parseBlock()
+		expression.ConConPairs = append(expression.ConConPairs, pair)
+	}
+
+	if p.curTokenIs(token.ELSE) {
 		expression.Alternative = p.parseBlock()
 	}
+
 	return expression
 }

parser/parser_test.go

@@ -443,17 +443,17 @@ func TestIfExpression(t *testing.T) {
 		t.Fatalf("stmt.Expression is not ast.IfExpression. got=%T", stmt.Expression)
 	}
 
-	if !testInfix(t, exp.Condition, "x", "<", "y") {
+	if !testInfix(t, exp.ConConPairs[0].Condition, "x", "<", "y") {
 		return
 	}
 
-	if len(exp.Consequence.Statements) != 1 {
+	if len(exp.ConConPairs[0].Consequence.Statements) != 1 {
 		t.Errorf("consequence is not 1 statements. got=%d\n", len(program.Statements))
 	}
 
-	consequence, ok := exp.Consequence.Statements[0].(*ast.ExpressionStatement)
+	consequence, ok := exp.ConConPairs[0].Consequence.Statements[0].(*ast.ExpressionStatement)
 	if !ok {
-		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T", exp.Consequence.Statements[0])
+		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T", exp.ConConPairs[0].Consequence.Statements[0])
 	}
 
 	if !testIdentifier(t, consequence.Expression, "x") {

tests/if.expected

@@ -0,0 +1,2 @@
+"single if"
+nil

tests/if.rl

@@ -0,0 +1,3 @@
+if (true)
+  puts("single if")
+end

tests/ifelif.expected

@@ -0,0 +1,3 @@
+"if/elif: if block"
+"if/elif: elif block"
+nil

tests/ifelif.rl

@@ -0,0 +1,10 @@
+i = 0
+while (i<2)
+  if (i==0)
+    puts("if/elif: if block")
+  elif (i==1)
+    puts("if/elif: elif block")
+  end
+
+  i = i+1
+end

tests/ifelifelifelse.expected

@@ -0,0 +1,5 @@
+"if/elif/el: if block"
+"if/elif/elif/el: first elif block"
+"if/elif/elif/el: second elif block"
+"if/elif/else: else block"
+nil

tests/ifelifelifelse.rl

@@ -0,0 +1,14 @@
+i = 0
+while (i<4)
+  if (i==0)
+    puts("if/elif/el: if block")
+  elif (i==1)
+    puts("if/elif/elif/el: first elif block")
+  elif (i==2)
+    puts("if/elif/elif/el: second elif block")
+  else
+    puts("if/elif/else: else block")
+  end
+
+  i = i+1
+end

tests/ifelifelse.expected

@@ -0,0 +1,4 @@
+"if/elif/el: if block"
+"if/elif/el: elif block"
+"if/elif/el: else block"
+nil

tests/ifelifelse.rl

@@ -0,0 +1,12 @@
+i = 0
+while (i<3)
+  if (i==0)
+    puts("if/elif/el: if block")
+  elif (i==1)
+    puts("if/elif/el: elif block")
+  else
+    puts("if/elif/el: else block")
+  end
+
+  i = i+1
+end

tests/ifelse.expected

@@ -0,0 +1,3 @@
+"if/else: if block"
+"if/else: else block"
+nil

tests/ifelse.rl

@@ -0,0 +1,10 @@
+i = 0
+while (i<2)
+  if (i==0)
+    puts("if/else: if block")
+  else
+    puts("if/else: else block")
+  end
+
+  i = i+1
+end

token/token.go

@@ -56,6 +56,7 @@ const (
 	TRUE     = "TRUE"
 	FALSE    = "FALSE"
 	IF       = "IF"
+	ELIF     = "ELIF"
 	ELSE     = "ELSE"
 	END      = "END"
 	RETURN   = "RETURN"
@@ -90,6 +91,7 @@ var keywords = map[string]TokenType{
 	"true":    TRUE,
 	"false":   FALSE,
 	"if":      IF,
+	"elif":    ELIF,
 	"end":     END,
 	"else":    ELSE,
 	"return":  RETURN,