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if.go
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if.go
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package yakast
import (
yak "github.com/yaklang/yaklang/common/yak/antlr4yak/parser"
"github.com/yaklang/yaklang/common/yak/antlr4yak/yakvm"
"github.com/google/uuid"
)
func (y *YakCompiler) VisitIfStmt(raw yak.IIfStmtContext) interface{} {
if y == nil || raw == nil {
return nil
}
i, _ := raw.(*yak.IfStmtContext)
if i == nil {
return nil
}
ifBlock := i.Block(0)
if ifBlock == nil {
y.panicCompilerError(compileError, "no if code block")
}
recoverRange := y.SetRange(ifBlock)
defer recoverRange()
y.writeString("if ")
tableRecover := y.SwitchSymbolTableInNewScope("if", uuid.New().String())
ifCond := i.Expression(0)
if ifCond == nil {
y.panicCompilerError(compileError, "no if condition")
}
y.VisitExpression(ifCond)
y.writeString(" ")
// if 条件为真,执行 if 语句块
// 使用 jmpf 来实现,如果 pop stack 之后的值被认为是 false,则跳转
var jmpfCode = y.pushJmpIfFalse()
// 编译 block
y.VisitBlock(ifBlock)
var jmpToEnd []*yakvm.Code
jmpToEnd = append(jmpToEnd, y.pushJmp())
// 为 jmpf 实现操作
jmpfCode.Unary = y.GetNextCodeIndex()
tableRecover()
for index := range i.AllElif() {
tableRecover = y.SwitchSymbolTableInNewScope("elif", uuid.New().String())
// elif 和 if 逻辑是一摸一样的,读一个 expression
// 然后使用 jmpf 跳转
// 但是 elif 有一个特殊的地方,就是需要在 if 语句块执行完毕之后
// 跳过 elif 语句块,所以需要在 elif 语句块的最后添加一个 jmp 指令
y.writeStringWithWhitespace("elif")
y.VisitExpression(i.Expression(index + 1))
y.writeString(" ")
var jmpfCode = y.pushJmpIfFalse()
y.VisitBlock(i.Block(index + 1))
jmpToEnd = append(jmpToEnd, y.pushJmp())
jmpfCode.Unary = y.GetNextCodeIndex()
tableRecover()
}
// 为 else 设置好结尾符
if ielseBlock := i.ElseBlock(); ielseBlock != nil {
elseBlock := ielseBlock.(*yak.ElseBlockContext)
y.writeStringWithWhitespace("else")
block := elseBlock.Block()
elseIf := elseBlock.IfStmt()
if block != nil {
tableRecover = y.SwitchSymbolTableInNewScope("else", uuid.New().String())
y.VisitBlock(block)
tableRecover()
} else if elseIf != nil {
y.VisitIfStmt(elseIf)
}
}
endCode := y.GetCodeIndex()
for _, jmp := range jmpToEnd {
jmp.Unary = endCode
}
return nil
}