:@eval
@eval
Evaluate an expression and return the value.
Examples
In the Julia programming language, the @eval
macro is used to evaluate an expression and return its value.
julia> x = 5;
julia> @eval x + 10
15
This example evaluates the expression x + 10
, where x
is a variable defined earlier as 5. The @eval
macro allows us to dynamically evaluate expressions at runtime.
Here are a few common examples of how @eval
can be used:

Dynamic code generation:
julia> for i in 1:3 @eval println("Loop iteration $i") end
This code dynamically generates and evaluates expressions to print different messages based on the loop iteration.

Evaluating mathematical expressions:
julia> a = 2; julia> b = 3; julia> @eval c = sqrt($a + $b) 2.23606797749979
Here, the expression
sqrt(a + b)
is dynamically evaluated using the values of variablesa
andb
.  Dynamic function creation:
julia> name = "add_numbers"; julia> @eval function $(Symbol(name))(x, y) return x + y end
This example demonstrates how a function named
add_numbers
is dynamically created using the@eval
macro.
Common mistake example:
julia> @eval 5 + 10
ERROR: syntax: missing comma or ) in argument list
In this example, the mistake is not using parentheses to enclose the expression within @eval
. Always ensure that the expression is properly enclosed to avoid syntax errors.
See Also
User Contributed Notes
Add a Note
The format of note supported is markdown, use triple backtick to start and end a code block.