算术函数

算术函数

Cloud Firestore 中的所有算术函数都具有以下行为：

  • 如果任一输入参数为 NULL，则计算结果为 NULL。
  • 如果有任何实参为 NaN，则计算结果为 NaN。
  • 如果发生溢出或下溢，则生成错误。

此外，当算术函数接收多个不同类型的数值实参（例如：add(5.0, 6)）时，Cloud Firestore 会将这些实参隐式转换为范围最广的输入类型。如果仅提供 INT32 类型的输入值，则返回类型为 INT64。

名称 说明
ABS 返回 number 的绝对值
ADD 返回 x + y 的值
SUBTRACT 返回 x - y 的值
MULTIPLY 返回 x * y 的值
DIVIDE 返回 x / y 的值
MOD 返回 x / y 相除所得的余数
CEIL 返回 number 的向上取整值
FLOOR 返回 number 的向下取整值
ROUND 将 number 四舍五入到 places 位小数
POW 返回 base^exponent 的值
SQRT 返回 number 的平方根
EXP 返回欧拉数的 exponent 次幂
LN 返回 number 的自然对数
LOG 返回 number 的对数
LOG10 返回以 10 为底的 number 的对数
RAND 返回一个伪随机浮点数

ABS

语法：

abs[N <: INT32 | INT64 | FLOAT64](number: N) -> N

说明：

返回 number 的绝对值。

  • 当函数可能导致 INT32 或 INT64 类型的值溢出时，将抛出错误。

示例：

数值 abs(number)
10 10
-10 10
10L 10L
-0.0 0.0
10.5 10.5
-10.5 10.5
-231 [error]
-263 [error]

添加

语法：

add[N <: INT32 | INT64 | FLOAT64](x: N, y: N) -> N

说明：

返回 x + y 的值。

示例：

x y add(x, y)
20 3 23
10.0 1 11.0
22.5 2.0 24.5
INT64.MAX 1 [error]
INT64.MIN -1 [error]

Web

const result = await execute(db.pipeline()
  .collection("books")
  .select(field("soldBooks").add(field("unsoldBooks")).as("totalBooks"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .select([Field("soldBooks").add(Field("unsoldBooks")).as("totalBooks")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .select(Expression.add(field("soldBooks"), field("unsoldBooks")).alias("totalBooks"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(Expression.add(field("soldBooks"), field("unsoldBooks")).alias("totalBooks"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .select(Field.of("soldBooks").add(Field.of("unsoldBooks")).as_("totalBooks"))
    .execute()
)
firestore_pipelines.py

SUBTRACT

语法：

subtract[N <: INT32 | INT64 | FLOAT64](x: N, y: N) -> N

说明：

返回 x - y 的值。

示例：

x y subtract(x, y)
20 3 17
10.0 1 9.0
22.5 2.0 20.5
INT64.MAX -1 [error]
INT64.MIN 1 [error]

Web

const storeCredit = 7;
const result = await execute(db.pipeline()
  .collection("books")
  .select(field("price").subtract(constant(storeCredit)).as("totalCost"))
);
test.firestore.js
Swift
let storeCredit = 7
let result = try await db.pipeline()
  .collection("books")
  .select([Field("price").subtract(Constant(storeCredit)).as("totalCost")])
  .execute()
PipelineSnippets.swift

Kotlin

val storeCredit = 7
val result = db.pipeline()
    .collection("books")
    .select(Expression.subtract(field("price"), storeCredit).alias("totalCost"))
    .execute()
DocSnippets.kt

Java

int storeCredit = 7;
Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(Expression.subtract(field("price"), storeCredit).alias("totalCost"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

store_credit = 7
result = (
    client.pipeline()
    .collection("books")
    .select(Field.of("price").subtract(store_credit).as_("totalCost"))
    .execute()
)
firestore_pipelines.py

MULTIPLY

语法：

multiply[N <: INT32 | INT64 | FLOAT64](x: N, y: N) -> N

说明：

返回 x * y 的值。

示例：

x y multiply(x, y)
20 3 60
10.0 1 10.0
22.5 2.0 45.0
INT64.MAX 2 [error]
INT64.MIN 2 [error]
FLOAT64.MAX FLOAT64.MAX +inf

Web

const result = await execute(db.pipeline()
  .collection("books")
  .select(field("price").multiply(field("soldBooks")).as("revenue"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .select([Field("price").multiply(Field("soldBooks")).as("revenue")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .select(Expression.multiply(field("price"), field("soldBooks")).alias("revenue"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(Expression.multiply(field("price"), field("soldBooks")).alias("revenue"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .select(Field.of("price").multiply(Field.of("soldBooks")).as_("revenue"))
    .execute()
)
firestore_pipelines.py

DIVIDE

语法：

divide[N <: INT32 | INT64 | FLOAT64](x: N, y: N) -> N

说明：

返回 x / y 的值。 整数除法的结果会被截断。

示例：

x y divide(x, y)
20 3 6
10.0 3 3.333...
22.5 2 11.25
10 0 [error]
1.0 0.0 +inf
-1.0 0.0 -inf

Web

const result = await execute(db.pipeline()
  .collection("books")
  .select(field("ratings").divide(field("soldBooks")).as("reviewRate"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .select([Field("ratings").divide(Field("soldBooks")).as("reviewRate")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .select(Expression.divide(field("ratings"), field("soldBooks")).alias("reviewRate"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(Expression.divide(field("ratings"), field("soldBooks")).alias("reviewRate"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .select(Field.of("ratings").divide(Field.of("soldBooks")).as_("reviewRate"))
    .execute()
)
firestore_pipelines.py

MOD

语法：

mod[N <: INT32 | INT64 | FLOAT64](x: N, y: N) -> N

说明：

返回 x / y 的余数。

  • 对于整数类型 (INT64)，当除数 y 为零时，系统会抛出 error。
  • 对于浮点类型 (FLOAT64)，当除数 y 为零时，函数返回 NaN。

示例：

x y mod(x, y)
20 3 2
-10 3 -1
10 -3 1
-10 -3 -1
10 1 0
22.5 2 0.5
22.5 0.0 NaN
25 0 [error]

Web

const displayCapacity = 1000;
const result = await execute(db.pipeline()
  .collection("books")
  .select(field("unsoldBooks").mod(constant(displayCapacity)).as("warehousedBooks"))
);
test.firestore.js
Swift
let displayCapacity = 1000
let result = try await db.pipeline()
  .collection("books")
  .select([Field("unsoldBooks").mod(Constant(displayCapacity)).as("warehousedBooks")])
  .execute()
PipelineSnippets.swift

Kotlin

val displayCapacity = 1000
val result = db.pipeline()
    .collection("books")
    .select(Expression.mod(field("unsoldBooks"), displayCapacity).alias("warehousedBooks"))
    .execute()
DocSnippets.kt

Java

int displayCapacity = 1000;
Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(Expression.mod(field("unsoldBooks"), displayCapacity).alias("warehousedBooks"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

display_capacity = 1000
result = (
    client.pipeline()
    .collection("books")
    .select(Field.of("unsoldBooks").mod(display_capacity).as_("warehousedBooks"))
    .execute()
)
firestore_pipelines.py

CEIL

语法：

ceil[N <: INT32 | INT64 | FLOAT64](number: N) -> N

说明：

返回大于或等于 number 的最小整数值。

示例：

数值 ceil(number)
20 20
10 10
0 0
24L 24L
-0.4 -0.0
0.4 1.0
22.5 23.0
+inf +inf
-inf -inf

Web

const booksPerShelf = 100;
const result = await execute(db.pipeline()
  .collection("books")
  .select(
    field("unsoldBooks").divide(constant(booksPerShelf)).ceil().as("requiredShelves")
  )
);
test.firestore.js
Swift
let booksPerShelf = 100
let result = try await db.pipeline()
  .collection("books")
  .select([
    Field("unsoldBooks").divide(Constant(booksPerShelf)).ceil().as("requiredShelves")
  ])
  .execute()
PipelineSnippets.swift

Kotlin

val booksPerShelf = 100
val result = db.pipeline()
    .collection("books")
    .select(
        Expression.divide(field("unsoldBooks"), booksPerShelf).ceil().alias("requiredShelves")
    )
    .execute()
DocSnippets.kt

Java

int booksPerShelf = 100;
Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(
        Expression.divide(field("unsoldBooks"), booksPerShelf).ceil().alias("requiredShelves")
    )
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

books_per_shelf = 100
result = (
    client.pipeline()
    .collection("books")
    .select(
        Field.of("unsoldBooks")
        .divide(books_per_shelf)
        .ceil()
        .as_("requiredShelves")
    )
    .execute()
)
firestore_pipelines.py

FLOOR

语法：

floor[N <: INT32 | INT64 | FLOAT64](number: N) -> N

说明：

返回小于或等于 number 的最大整数值。

示例：

数值 floor(number)
20 20
10 10
0 0
2147483648 2147483648
-0.4 -1.0
0.4 0.0
22.5 22.0
+inf +inf
-inf -inf

Web

const result = await execute(db.pipeline()
  .collection("books")
  .addFields(
    field("wordCount").divide(field("pages")).floor().as("wordsPerPage")
  )
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .addFields([
    Field("wordCount").divide(Field("pages")).floor().as("wordsPerPage")
  ])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .addFields(
        Expression.divide(field("wordCount"), field("pages")).floor().alias("wordsPerPage")
    )
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .addFields(
        Expression.divide(field("wordCount"), field("pages")).floor().alias("wordsPerPage")
    )
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .add_fields(
        Field.of("wordCount").divide(Field.of("pages")).floor().as_("wordsPerPage")
    )
    .execute()
)
firestore_pipelines.py

ROUND

语法：

round[N <: INT32 | INT64 | FLOAT64 | DECIMAL128](number: N) -> N
round[N <: INT32 | INT64 | FLOAT64 | DECIMAL128](number: N, places: INT64) -> N

说明：

将数值 number 按 places 指定的位数进行舍入。如果 places 为正数，则对小数点右侧的数字进行舍入；如果为负数，则对小数点左侧的数字进行舍入。

  • 如果仅提供 number，则会四舍五入到最接近的整数。
  • 中间数向远离 0 的方向舍入。
  • 如果使用负 places 值进行舍入导致溢出，则会抛出 error。

示例：

数值 位数 round(number, places)
15.5 0 16.0
-15.5 0 -16.0
15 1 15
15 0 15
15 -1 20
15 -2 0
15.48924 1 15.5
231-1 -1 [error]
263-1L -1 [error]

Web

const result = await execute(db.pipeline()
  .collection("books")
  .select(field("soldBooks").multiply(field("price")).round().as("partialRevenue"))
  .aggregate(field("partialRevenue").sum().as("totalRevenue"))
  );
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .select([Field("soldBooks").multiply(Field("price")).round().as("partialRevenue")])
  .aggregate([Field("partialRevenue").sum().as("totalRevenue")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .select(Expression.multiply(field("soldBooks"), field("price")).round().alias("partialRevenue"))
    .aggregate(AggregateFunction.sum("partialRevenue").alias("totalRevenue"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(Expression.multiply(field("soldBooks"), field("price")).round().alias("partialRevenue"))
    .aggregate(AggregateFunction.sum("partialRevenue").alias("totalRevenue"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .select(
        Field.of("soldBooks")
        .multiply(Field.of("price"))
        .round()
        .as_("partialRevenue")
    )
    .aggregate(Field.of("partialRevenue").sum().as_("totalRevenue"))
    .execute()
)
firestore_pipelines.py

POW

语法：

pow(base: FLOAT64, exponent: FLOAT64) -> FLOAT64

说明：

返回 base 的 exponent 次幂。

  • 如果 base <= 0 且 exponent 不为整数，则会抛出错误。

  • 对于任何 exponent，pow(1, exponent) 均为 1。

  • 对于任何 base，pow(base, 0) 均为 1。

示例：

base exponent pow(base, exponent)
2 3 8.0
2 -3 0.125
+inf 0 1.0
1 +inf 1.0
-1 0.5 [error]
0 -1 [error]

Web

const googleplex = { latitude: 37.4221, longitude: 122.0853 };
const result = await execute(db.pipeline()
  .collection("cities")
  .addFields(
    field("lat").subtract(constant(googleplex.latitude))
      .multiply(111 /* km per degree */)
      .pow(2)
      .as("latitudeDifference"),
    field("lng").subtract(constant(googleplex.longitude))
      .multiply(111 /* km per degree */)
      .pow(2)
      .as("longitudeDifference")
  )
  .select(
    field("latitudeDifference").add(field("longitudeDifference")).sqrt()
      // Inaccurate for large distances or close to poles
      .as("approximateDistanceToGoogle")
  )
);
test.firestore.js
Swift
let googleplex = CLLocation(latitude: 37.4221, longitude: 122.0853)
let result = try await db.pipeline()
  .collection("cities")
  .addFields([
    Field("lat").subtract(Constant(googleplex.coordinate.latitude))
      .multiply(111 /* km per degree */)
      .pow(2)
      .as("latitudeDifference"),
    Field("lng").subtract(Constant(googleplex.coordinate.latitude))
      .multiply(111 /* km per degree */)
      .pow(2)
      .as("longitudeDifference")
  ])
  .select([
    Field("latitudeDifference").add(Field("longitudeDifference")).sqrt()
      // Inaccurate for large distances or close to poles
      .as("approximateDistanceToGoogle")
  ])
  .execute()
PipelineSnippets.swift

Kotlin

val googleplex = GeoPoint(37.4221, -122.0853)
val result = db.pipeline()
    .collection("cities")
    .addFields(
        field("lat").subtract(googleplex.latitude)
            .multiply(111 /* km per degree */)
            .pow(2)
            .alias("latitudeDifference"),
        field("lng").subtract(googleplex.longitude)
            .multiply(111 /* km per degree */)
            .pow(2)
            .alias("longitudeDifference")
    )
    .select(
        field("latitudeDifference").add(field("longitudeDifference")).sqrt()
            // Inaccurate for large distances or close to poles
            .alias("approximateDistanceToGoogle")
    )
    .execute()
DocSnippets.kt

Java

GeoPoint googleplex = new GeoPoint(37.4221, -122.0853);
Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("cities")
    .addFields(
        field("lat").subtract(googleplex.getLatitude())
            .multiply(111 /* km per degree */)
            .pow(2)
            .alias("latitudeDifference"),
        field("lng").subtract(googleplex.getLongitude())
            .multiply(111 /* km per degree */)
            .pow(2)
            .alias("longitudeDifference")
    )
    .select(
        field("latitudeDifference").add(field("longitudeDifference")).sqrt()
            // Inaccurate for large distances or close to poles
            .alias("approximateDistanceToGoogle")
    )
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

googleplexLat = 37.4221
googleplexLng = -122.0853
result = (
    client.pipeline()
    .collection("cities")
    .add_fields(
        Field.of("lat")
        .subtract(googleplexLat)
        .multiply(111)  # km per degree
        .pow(2)
        .as_("latitudeDifference"),
        Field.of("lng")
        .subtract(googleplexLng)
        .multiply(111)  # km per degree
        .pow(2)
        .as_("longitudeDifference"),
    )
    .select(
        Field.of("latitudeDifference")
        .add(Field.of("longitudeDifference"))
        .sqrt()
        # Inaccurate for large distances or close to poles
        .as_("approximateDistanceToGoogle")
    )
    .execute()
)
firestore_pipelines.py

SQRT

语法：

sqrt[N <: FLOAT64 | DECIMAL128](number: N) -> N

说明：

返回 number 的平方根。

  • 如果 number 为负数，函数将抛出 error。

示例：

数值 sqrt(number)
25 5.0
12.002 3.464...
0.0 0.0
NaN NaN
+inf +inf
-inf [error]
x < 0 [error]

Web

const googleplex = { latitude: 37.4221, longitude: 122.0853 };
const result = await execute(db.pipeline()
  .collection("cities")
  .addFields(
    field("lat").subtract(constant(googleplex.latitude))
      .multiply(111 /* km per degree */)
      .pow(2)
      .as("latitudeDifference"),
    field("lng").subtract(constant(googleplex.longitude))
      .multiply(111 /* km per degree */)
      .pow(2)
      .as("longitudeDifference")
  )
  .select(
    field("latitudeDifference").add(field("longitudeDifference")).sqrt()
      // Inaccurate for large distances or close to poles
      .as("approximateDistanceToGoogle")
  )
);
test.firestore.js
Swift
let googleplex = CLLocation(latitude: 37.4221, longitude: 122.0853)
let result = try await db.pipeline()
  .collection("cities")
  .addFields([
    Field("lat").subtract(Constant(googleplex.coordinate.latitude))
      .multiply(111 /* km per degree */)
      .pow(2)
      .as("latitudeDifference"),
    Field("lng").subtract(Constant(googleplex.coordinate.latitude))
      .multiply(111 /* km per degree */)
      .pow(2)
      .as("longitudeDifference")
  ])
  .select([
    Field("latitudeDifference").add(Field("longitudeDifference")).sqrt()
      // Inaccurate for large distances or close to poles
      .as("approximateDistanceToGoogle")
  ])
  .execute()
PipelineSnippets.swift

Kotlin

val googleplex = GeoPoint(37.4221, -122.0853)
val result = db.pipeline()
    .collection("cities")
    .addFields(
        field("lat").subtract(googleplex.latitude)
            .multiply(111 /* km per degree */)
            .pow(2)
            .alias("latitudeDifference"),
        field("lng").subtract(googleplex.longitude)
            .multiply(111 /* km per degree */)
            .pow(2)
            .alias("longitudeDifference")
    )
    .select(
        field("latitudeDifference").add(field("longitudeDifference")).sqrt()
            // Inaccurate for large distances or close to poles
            .alias("approximateDistanceToGoogle")
    )
    .execute()
DocSnippets.kt

Java

GeoPoint googleplex = new GeoPoint(37.4221, -122.0853);
Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("cities")
    .addFields(
        field("lat").subtract(googleplex.getLatitude())
            .multiply(111 /* km per degree */)
            .pow(2)
            .alias("latitudeDifference"),
        field("lng").subtract(googleplex.getLongitude())
            .multiply(111 /* km per degree */)
            .pow(2)
            .alias("longitudeDifference")
    )
    .select(
        field("latitudeDifference").add(field("longitudeDifference")).sqrt()
            // Inaccurate for large distances or close to poles
            .alias("approximateDistanceToGoogle")
    )
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

googleplexLat = 37.4221
googleplexLng = -122.0853
result = (
    client.pipeline()
    .collection("cities")
    .add_fields(
        Field.of("lat")
        .subtract(googleplexLat)
        .multiply(111)  # km per degree
        .pow(2)
        .as_("latitudeDifference"),
        Field.of("lng")
        .subtract(googleplexLng)
        .multiply(111)  # km per degree
        .pow(2)
        .as_("longitudeDifference"),
    )
    .select(
        Field.of("latitudeDifference")
        .add(Field.of("longitudeDifference"))
        .sqrt()
        # Inaccurate for large distances or close to poles
        .as_("approximateDistanceToGoogle")
    )
    .execute()
)
firestore_pipelines.py

EXP

语法：

exp(exponent: FLOAT64) -> FLOAT64

说明：

返回欧拉数 (e) 的 exponent 次幂的值，该函数也称为自然指数函数。

示例：

exponent exp(exponent)
0.0 1.0
10 e^10 (FLOAT64)
+inf +inf
-inf 0

Web

const result = await execute(db.pipeline()
  .collection("books")
  .select(field("rating").exp().as("expRating"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .select([Field("rating").exp().as("expRating")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .select(field("rating").exp().alias("expRating"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(field("rating").exp().alias("expRating"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .select(Field.of("rating").exp().as_("expRating"))
    .execute()
)
firestore_pipelines.py

LN

语法：

ln(number: FLOAT64) -> FLOAT64

说明：

返回 number 的自然对数。 此函数等效于 log(number)。

示例：

数值 ln(number)
1 0.0
2L 0.693...
1.0 0.0
e (FLOAT64) 1.0
-inf NaN
+inf +inf
x <= 0 [error]

Web

const result = await execute(db.pipeline()
  .collection("books")
  .select(field("rating").ln().as("lnRating"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .select([Field("rating").ln().as("lnRating")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .select(field("rating").ln().alias("lnRating"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(field("rating").ln().alias("lnRating"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .select(Field.of("rating").ln().as_("lnRating"))
    .execute()
)
firestore_pipelines.py

LOG

语法：

log(number: FLOAT64, base: FLOAT64) -> FLOAT64
log(number: FLOAT64) -> FLOAT64

说明：

返回以 base 为底的 number 的对数。

  • 如果仅提供 number，则返回以 base 为底的 number 的对数（相当于 ln(number)）。

示例：

数值 base log(number, base)
100 10 2.0
-inf Numeric NaN
Numeric。 +inf NaN
number <= 0 Numeric [error]
Numeric base <= 0 [error]
Numeric 1.0 [error]

LOG10

语法：

log10(x: FLOAT64) -> FLOAT64

说明：

返回以 10 为底的 number 的对数。

示例：

数值 log10(number)
100 2.0
-inf NaN
+inf +inf
x <= 0 [error]

RAND

语法：

rand() -> FLOAT64

说明：

返回一个伪随机浮点数，该数均匀地取自 0.0（含）和 1.0（不含）之间。