Fortran 简明教程

Fortran - Operators

运算符是一个告诉编译器执行特定数学或逻辑操作的符号。Fortran 提供以下类型的运算符 -

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. Fortran provides the following types of operators −

Arithmetic Operators
Relational Operators
Logical Operators

让我们逐个查看所有这些类型的运算符。

Let us look at all these types of operators one by one.

Arithmetic Operators

下表显示了 Fortran 支持的所有算术运算符。假设变量 A 保存 5，变量 B 保存 3，则 -

Following table shows all the arithmetic operators supported by Fortran. Assume variable A holds 5 and variable B holds 3 then −

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Operator

Description

Example

Addition Operator, adds two operands.

A + B will give 8

Subtraction Operator, subtracts second operand from the first.

A - B will give 2

Multiplication Operator, multiplies both operands.

A * B will give 15

Division Operator, divides numerator by de-numerator.

A / B will give 1

Exponentiation Operator, raises one operand to the power of the other.

A ** B will give 125

Relational Operators

下表显示了 Fortran 支持的所有关系运算符。假设变量 A 为 10，变量 B 为 20，则 −

Following table shows all the relational operators supported by Fortran. Assume variable A holds 10 and variable B holds 20, then −

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Operator

Equivalent

Description

Example

.eq.

Checks if the values of two operands are equal or not, if yes then condition becomes true.

(A == B) is not true.

.ne.

Checks if the values of two operands are equal or not, if values are not equal then condition becomes true.

(A != B) is true.

.gt.

Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.

(A > B) is not true.

.lt.

Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.

(A < B) is true.

.ge.

Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.

(A >= B) is not true.

⇐

.le.

Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.

(A ⇐ B) is true.

Logical Operators

Fortran 中的逻辑运算符仅针对逻辑值 .true. 和 .false. 工作。

Logical operators in Fortran work only on logical values .true. and .false.

下表显示了 Fortran 支持的所有逻辑运算符。假设变量 A 为 .true.，变量 B 为 .false.，则 −

The following table shows all the logical operators supported by Fortran. Assume variable A holds .true. and variable B holds .false. , then −

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Operator

Description

Example

.and.

Called Logical AND operator. If both the operands are non-zero, then condition becomes true.

(A .and. B) is false.

.or.

Called Logical OR Operator. If any of the two operands is non-zero, then condition becomes true.

(A .or. B) is true.

.not.

Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.

!(A .and. B) is true.

.eqv.

Called Logical EQUIVALENT Operator. Used to check equivalence of two logical values.

(A .eqv. B) is false.

.neqv.

Called Logical NON-EQUIVALENT Operator. Used to check non-equivalence of two logical values.

(A .neqv. B) is true.

Operators Precedence in Fortran

运算符优先级确定表达式中项的分组。这会影响表达式的求值方式。某些运算符比其他运算符具有更高的优先级；例如，乘法运算符的优先级高于加法运算符。

Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator.

例如，x = 7 + 3 * 2；此处，x 被赋值为 13，而不是 20，因为运算符 * 优先级高于 +，因此其首先与 3*2 相乘，然后加到 7 中。

For example, x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has higher precedence than +, so it first gets multiplied with 3*2 and then adds into 7.

此处，优先级最高的运算符显示在表顶部，优先级最低的运算符显示在表底部。在表达式中，将首先评估优先级较高的运算符。

Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.

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