发布日期: 09/18/2023

Expression Functions

Arg(expr, i)

Arg Expr(expr, i)

Description

Finds the argument numbered by i within the given expression.

Returns

The ith argument within the expression expr.

Empty() if that argument does not exist or is not specified.

Arguments

expr

An expression.

i

An integer that indicates which argument to return.

Notes

Arg Expr() is deprecated. Use Arg() instead.

Eval Expr(expr)

Description

Evaluates any expressions within expr, but leaves the outer expression unevaluated.

Returns

An expression with all the expressions inside expr evaluated.

Argument

expr

A valid expression.

Expr(expr, i)

Description

Returns the argument unevaluated (expression-quoting).

Returns

The argument, unevaluated.

Empty() if that argument does not exist or is not specified.

Argument

expr

An expression.

i

An integer that indicates which argument to return.

Extract Expr(expr, pattern)

Description

Find expr matching pattern.

Returns

A pattern that matches the specified pattern.

Arguments

expr

An expression.

pattern

Any pattern.

Head(exprArg)

Head Expr(exprArg)

Description

Returns the head of the evaluated expression, without its arguments.

Notes

Head Expr() is deprecated. Use Head() instead.

Head Name(expr)

Head Name Expr(expr)

Description

Returns the head of the evaluated expression as a quoted string.

Notes

Head Name Expr() is deprecated. Use Head Name() instead.

N Arg(exprArg)

Description

Returns the number of arguments of the evaluated expression head.

N Arg Expr(exprArg)

Description

Returns the number of arguments of the expression head.

Notes

N Arg Expr() is deprecated. Use N Arg() instead.

Name Expr(x)

Description

Returns the unevaluated expression of x rather than the evaluation of x.

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