0 a number or quantity that has something done to it in a calculation. For example, in 7 + y, 7 and y are the operands. -- 运算对象
The first step is to evaluate the operator and operand.
In function application, the operator is first evaluated to a function; it is then applied to the operand whose evaluation is suspended in an abstraction.
So, two rewrites within the operator of a function application can be merged into one even when separated by a rewrite within the operand.
The chain of append operations in the last line is reasonably efficient since the first three operands usually are extremely short lists.
We want to emit instructions by name and to have the assembler make sure the types and values of the operands are sensible.
The generating code controls the order and number of the copies, and it overwrites certain operands in the template, called holes, with new values.
At a function application the value is only allowed to propagate when 'unchanged' is obtained for both the operator and the operand.
This suggests that operand intrusions were reduced when the cued language had been inhibited on the preceding trial.
