How can one generate expression trees using lambda?

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One way to generate expression trees using lambda is to define a hierarchy of lambda functions that represent the nodes of the tree. Each lambda function would take one or more lambda expressions as arguments and return a higher-level lambda expression that combines them. For example, the lambda function for addition might take two lambda expressions as arguments and return a lambda expression that applies the plus operator to their evaluated results:

add = lambda x, y: (lambda: x() + y())

Similarly, the lambda function for multiplication might take two lambda expressions as arguments and return a lambda expression that applies the times operator to their evaluated results:

mul = lambda x, y: (lambda: x() * y())

By defining such functions for all the operations and using them recursively to build up more complex expressions, one could construct an expression tree entirely in lambda form. For instance, the expression tree for the expression "3 + 4 * 5" could be constructed as follows:

add(3, mul(4, 5))