If

A conditional statement.

声明

语法

If(identifier? name, expr test, stmt* body, stmt* orelse)

参数

Argument	描述
name	the construct name, or nil.
test	the condition, of a logical type.
body	the statements run when the condition is true.
orelse	the statements run when it is false. else if is an If nested in orelse.

返回值

无。

描述

test must already be logical: ASR has no notion of a value being truthy, so a frontend that allows one inserts the comparison itself.

There is no else if node. else if is an If whose parent’s orelse holds exactly it, which keeps the tree uniform for passes that rewrite conditionals.

示例

(If
  :name nil
  :test (IntegerCompare
    :left (Var
      :v (SymbolRef 1 "i")
    )
    :op :Eq
    :right (IntegerConstant
      :n 5
      :type (Integer
        :kind 4
      )
      :intboz_type :Decimal
    )
    :type (Logical
      :kind 4
    )
    :value nil
  )
  :body [
    (Cycle
      :stmt_name "loop"
    )
  ]
  :orelse []
)

It comes from this complete ASR text document:

(TranslationUnit
  :symtab (SymbolTable
    :id 0
    :symbols {
      "main" (Program
        :symtab (SymbolTable
          :id 1
          :symbols {
            "i" (Variable
              :parent_symtab 1
              :name "i"
              :dependencies []
              :intent :Local
              :symbolic_value nil
              :value nil
              :storage :Default
              :type (Integer
                :kind 4
              )
              :type_declaration nil
              :abi :Source
              :access :Public
              :presence :Required
              :value_attr false
              :target_attr false
              :contiguous_attr false
              :bindc_name nil
              :is_volatile false
              :is_protected false
              :pass_attr :NotMethod
              :self_argument nil
              :codims []
            )
            "j" (Variable
              :parent_symtab 1
              :name "j"
              :dependencies []
              :intent :Local
              :symbolic_value nil
              :value nil
              :storage :Default
              :type (Integer
                :kind 4
              )
              :type_declaration nil
              :abi :Source
              :access :Public
              :presence :Required
              :value_attr false
              :target_attr false
              :contiguous_attr false
              :bindc_name nil
              :is_volatile false
              :is_protected false
              :pass_attr :NotMethod
              :self_argument nil
              :codims []
            )
            "p" (Variable
              :parent_symtab 1
              :name "p"
              :dependencies []
              :intent :Local
              :symbolic_value nil
              :value nil
              :storage :Default
              :type (Logical
                :kind 4
              )
              :type_declaration nil
              :abi :Source
              :access :Public
              :presence :Required
              :value_attr false
              :target_attr false
              :contiguous_attr false
              :bindc_name nil
              :is_volatile false
              :is_protected false
              :pass_attr :NotMethod
              :self_argument nil
              :codims []
            )
          }
        )
        :name "main"
        :dependencies []
        :body [
          (DoLoop
            :name "loop"
            :head (do_loop_head
              :v (Var
                :v (SymbolRef 1 "i")
              )
              :start (IntegerConstant
                :n 1
                :type (Integer
                  :kind 4
                )
                :intboz_type :Decimal
              )
              :end (IntegerConstant
                :n 10
                :type (Integer
                  :kind 4
                )
                :intboz_type :Decimal
              )
              :increment (IntegerConstant
                :n 1
                :type (Integer
                  :kind 4
                )
                :intboz_type :Decimal
              )
            )
            :body [
              (If
                :name nil
                :test (IntegerCompare
                  :left (Var
                    :v (SymbolRef 1 "i")
                  )
                  :op :Eq
                  :right (IntegerConstant
                    :n 5
                    :type (Integer
                      :kind 4
                    )
                    :intboz_type :Decimal
                  )
                  :type (Logical
                    :kind 4
                  )
                  :value nil
                )
                :body [
                  (Cycle
                    :stmt_name "loop"
                  )
                ]
                :orelse []
              )
              (If
                :name nil
                :test (Var
                  :v (SymbolRef 1 "p")
                )
                :body [
                  (Exit
                    :stmt_name "loop"
                  )
                ]
                :orelse [
                  (Assignment
                    :target (Var
                      :v (SymbolRef 1 "j")
                    )
                    :value (Var
                      :v (SymbolRef 1 "i")
                    )
                    :overloaded nil
                    :realloc_lhs false
                    :move_allocation false
                  )
                ]
              )
            ]
            :orelse []
          )
          (WhileLoop
            :name nil
            :test (IntegerCompare
              :left (Var
                :v (SymbolRef 1 "j")
              )
              :op :Lt
              :right (IntegerConstant
                :n 100
                :type (Integer
                  :kind 4
                )
                :intboz_type :Decimal
              )
              :type (Logical
                :kind 4
              )
              :value nil
            )
            :body [
              (Assignment
                :target (Var
                  :v (SymbolRef 1 "j")
                )
                :value (IntegerBinOp
                  :left (Var
                    :v (SymbolRef 1 "j")
                  )
                  :op :Add
                  :right (IntegerConstant
                    :n 1
                    :type (Integer
                      :kind 4
                    )
                    :intboz_type :Decimal
                  )
                  :type (Integer
                    :kind 4
                  )
                  :value nil
                )
                :overloaded nil
                :realloc_lhs false
                :move_allocation false
              )
            ]
            :orelse []
          )
          (Assert
            :test (IntegerCompare
              :left (Var
                :v (SymbolRef 1 "j")
              )
              :op :GtE
              :right (IntegerConstant
                :n 0
                :type (Integer
                  :kind 4
                )
                :intboz_type :Decimal
              )
              :type (Logical
                :kind 4
              )
              :value nil
            )
            :msg (StringConstant
              :s "j is not negative"
              :type (String
                :kind 1
                :len (IntegerConstant
                  :n 17
                  :type (Integer
                    :kind 4
                  )
                  :intboz_type :Decimal
                )
                :len_kind :ExpressionLength
                :physical_type :DescriptorString
              )
            )
          )
        ]
      )
    }
  )
  :items []
)

也可以看看

IfExp, Select, Where, IfArithmetic