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eval

eval([m::Module], expr::Expr)

Evaluate an expression in the given module and return the result. Every Module (except those defined with baremodule) has its own 1-argument definition of eval, which evaluates expressions in that module.

Examples

1. Evaluate an expression in the current module:

   julia> x = 5;
   julia> eval(:(x + 10))
   15

   In this example, the expression x + 10 is evaluated in the current module, resulting in the value 15.

2. Evaluate an expression in a specific module:

   julia> mod = Module();
   julia> eval(mod, :(y = 20))
   20

   Here, the expression y = 20 is evaluated in the module mod, and the value 20 is returned.

3. Evaluate a dynamically constructed expression:

   julia> a = 2;
   julia> b = 3;
   julia> expr = :(a + b);
   julia> eval(expr)
   5

   This example demonstrates how to construct an expression using the : syntax and evaluate it using eval.

Common mistake example:

julia> eval([:x, :y, :z])
ERROR: MethodError: no method matching eval(::Array{Symbol,1})

In this example, an array of symbols [:x, :y, :z] is passed to eval instead of an Expr object. eval expects an expression, not an array of symbols. To evaluate multiple expressions, you can create a block expression using Expr(:block, ...) or use a loop to evaluate each symbol individually.

See Also

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