Merge pull request #198 from Flipez/implement-elseif

Implement `if / elif / else`

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,