I want to define the block as a string, then create the lambda. The following example does not work. Is something like this possible?
code_string = "|x|x*2"
l = lambda {eval(code_string)}
l.call(3) => 6
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A:
This works
eval "lambda { " + code_string + " }"
I just don't know why this one does and the other does not.
fjs6
2010-03-17 00:37:32
Calling lambda on an eval argument results in a Proc object with the eval call 'inside' the Proc object. The resulting Proc object doesn't take an argument, as the expression `eval(code_string)` doesn't take an argument. When you call the Proc object, it evals the code_string!The eval of the string "lambda { " + code_string + " }" gives a Proc object that is expecting an argument, and returns 2*argument.
Fred
2010-03-17 00:55:21
Also, it's more idiomatic (and more efficient to boot) to use string interpolation, so it would be: `eval "lambda {#{code_string}}"`. Concatenating several strings with `+` is rarely done in Ruby.
Chuck
2010-03-17 02:37:36