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I'm trying to define a block that I'll use to pass the the each method of multiple ranges. Rather than redefining the block on each range, I'd like to create a lamba, and pass the lambda as such:
count = 0 procedure = lambda {|v| map[count+=1]=v} ("A".."K").each procedure ("M".."N").each procedure ("P".."Z").each procedure However, I get the following error:
ArgumentError: wrong number of arguments(1 for 0) from code.rb:23:in `each'
Any ideas what's going on here?
804
When using parameters prefixed with ampersands, passing a block to a method results in a proc in the method's context. Procs behave like blocks, but they can be stored in a variable. Lambdas are procs that behave like methods, meaning they enforce arity and return as methods instead of in their parent scope.
Procs are objects, blocks are notA proc (notice the lowercase p) is an instance of the Proc class. This lets us call methods on it and assign it to variables. Procs can also return themselves. In contrast, a block is just part of the syntax of a method call.
In Ruby, a lambda is an object similar to a proc. Unlike a proc, a lambda requires a specific number of arguments passed to it, and it return s to its calling method rather than returning immediately. proc_demo = Proc.
With Ruby, the lambda keyword is used to create a lambda function. It requires a block and can define zero or more parameters. You call the resulting lambda function by using the call method. The literal operator is succinct and commonly used.
Tack an ampersand (&) onto the argument, for example:
("A".."K").each &procedure This signifies that you're passing it as the special block parameter of the method. Otherwise it's interpreted as a normal argument.
It also mirrors they way you'd capture and access the block parameter inside the method itself:
# the & here signifies that the special block parameter should be captured # into the variable `procedure` def some_func(foo, bar, &procedure) procedure.call(foo, bar) end some_func(2, 3) {|a, b| a * b } => 6 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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